1 ` 2019 Neuroanatomy Objectives
Frontal Lobe Central Sulcus Precentral Gyrus (Primary Motor Cortex – M1) Precentral Sulcus Brocca’s Area (Expressive Speech) Prefrontal Cortex (Cognition)
Parietal Lobe Postcentral Sulcus Postcentral Gyrus (Primary Sensory Cortex – S1) Central Sulcus
Occipital Lobe Calcarine Fissure Primary Visual Cortex (V1)
Temporal Lobe Superior Temporal Sulcus Heschl’s Gyrus (Primary Auditory Area –A1) Wernicke’s Area (Comprehensive Speech Area)
Limbic Lobe Structures Cingulate Gyrus (Cognition). Cingulate Sulcus Parahippocampal Gyrus (Memory) Uncus – Near Primary Olfactory Cortex (Smell).
2 Head and Neck Sensory Perception – Post Central Gyrus (S1), head area receives sensory information largely from cranial nerve V. Speech – Broca’s Area (speech production) and Wernicke’s Area (speech comprehension). Hearing – Primary Auditory Cortex (A1) Vision – Primary Visual Cortex (V1) (within the depths of the calcarine fissure) Smell –Limbic Cortex (Near Uncus)
Interhemispheric Commissures Corpus Callosum Anterior and Posterior Commissures
Diencephalon Thalamus (sensory relay to cortex and motor relay to cortex) Hypothalamus (basic physiologic drives and homeostasis) 3rd Ventricle
Pons and Cerebellum Superior Cerebellar Peduncle - white matter pathway (i.e., nerve fibers) connecting midbrain and cerebellum. Middle Cerebellar Peduncle -white matter pathway connecting pons and cerebellum. Inferior Cerebellar Peduncle -white matter pathway connecting medulla and cerebellum. 4th Ventricle
Medulla Pyramids Olives 4th Ventricle
Anterior Circulation (Internal Carotid Artery) Internal Carotid Artery Anterior Cerebral Artery Anterior Communicating Artery Middle Cerebral Artery Posterior Communicating Artery
3 Posterior Circulation (Vertebral and Basilar Arteries) Vertebral Arteries Posterior Spinal Arteries Posterior Inferior Cerebellar Artery (PICA) Anterior Spinal Artery Basilar Artery Anterior Inferior Cerebellar Artery (AICA) Superior Cerebellar Artery Posterior Cerebral Artery
CSF Cavities and Passageways Lateral Ventricle Foramen of Monro 3rd Ventricle Cerebral Aqueduct 4th Ventricle Cisterna Magna Superior Sagittal Sinus
Interventricular Lateral Ventricles 3rd Ventricle Foramen of Monro
Cisterna Magna Aqueduct of Sylvius Superior Sagittal (Cerebral Aqueduct) Sinus (Arachnoid Granulations) 4th Ventricle
Confluence of Sinuses
4 Meninges Dura matter - The external covering that forms the outermost layer of the meninges. Is dense connective tissue. Contains the sinuses and forms folds of septa (i.e. falx cerebri). Arachnoid matter - Middle layer of meninges. Web-like connective tissue matrix that does not enter sulci of cerebral cortex. The arachnoid is partly separated from the pia matter by the subarachnoid space which contains cerebrospinal fluid (CSF). Pia matter - Inner layer of meninges. Thin connective tissue membrane that adheres to the nervous tissue (faithfully follows the underlying nervous tissue of the central nervous system).
Folds of Dura Matter Falx cerebri – Sickle shaped sheet of dura that forms a partition between the two cerebral (cortical) hemispheres. Tentorium cerebelli- Fold of dura that separates the cerebral hemisphere from the cerebellum. (Forms roof over posterior cranial fossa). Falx cerebelli-Small sickle shaped fold of dura that extends slightly between the cerebellar hemispheres.
Venous Sinuses of the Dura Matter Superior sagittal sinus-Located within superior part of falx cerebri. Contains many arachnoid villa that constitute the main site of passage of CSF into the venous blood. Drains into the confluens of sinuses. Inferior sagittal sinus- Located on the free margin (inferior border) of the falx cerebri. Drains into the straight sinus. Straight sinus- Located in the tentorium cerebelli. Drains into the confluens of sinuses. Transverse sinus- Drains into the sigmoid sinus. Sigmoid sinus – Drains into the internal jugular vein. Superior and inferior petrosal sinuses- Both drain posteriorly. The inferior petrosal sinus drains into internal jugular vein and the superior petrosal sinus into sigmoid sinus. Cavernous sinus- Drains posteriorly into the superior and inferior petrosal sinuses.
Cranial Nerves (CN’s)
CN I – Olfactory CN VII - Facial CN II – Optic CN VIII -Vestibulocochlear CN III – Oculomotor CN IX - Glossopharyngeal CN IV – Trochlear CN X - Vagus CN V – Trigeminal CN XI - Accessory CN VI - Abducens CN XII-Hypoglossal
I. Cranial Fossae:
Anterior, Middle and Posterior Cranial Fossae
B. Middle cranial fossa – Formed by the sphenoid bone (greater wings, sella turcica), and temporal bone (petrous part, inner surface of squamous part). 1. Foramen: a. Optic canal - CN II and ophthalmic artery. b. Superior orbital fissure - Ophthalmic vein, CN V1, CN III, CN IV, CN VI, sympathetic fibers. c. Foramen rotundum - CN V2. d. Foramen ovale - CN V3. e. Foramen spinosum - Middle meningeal artery. f. Foramen lacerum - Internal carotid artery and greater petrosal nerve. g. Carotid Canal – below middle cranial fossa, contains internal carotid artery. g. Hiatus of greater petrosal nerve - Greater petrosal nerve (of CN VII). i. Hiatus for the lesser petrosal nerve - Lesser petrosal nerve (of CN IX).
C. Posterior cranial fossa - Formed by occipital bone, temporal bone (petrous part, mastoid part), and sphenoid bone (body). a. Foramen magnum - Spinal cord, meninges, CN XI, and spinal arteries. b. Jugular foramen - CN’s IX, X and XI, internal jugular vein, sigmoid sinus, inferior petrosal sinus. c. Hypoglossal canal - CN XII. d. Internal acoustic meatus - CN VII, CN VIII, labyrinthine (auditory) artery.
6 Foramina of the Skull
Anterior Ethmoidal Forman
Located in the petrous portion of the temporal bone. Contains the internal carotid artery, internal carotid plexus (sympathetic), and deep petrosal nerve (sympathetic) arising from the internal carotid plexus.
Located posterior to occipital condyle. Contains emissary vein linking the vertebral vein with the sigmoid sinus. Also called the posterior condylar canal (see hypoglossal canal for anterior condylar canal). Also may contain an arterial branch from the occipital artery that supplies the dura of the posterior cranial fossa.
Located at the medial end or apex of the petrous portion of the temporal bone, basal portion of the occipital bone, and sphenoid bone. It is spatially continuous with the carotid canal. During life the lower part floor of the foramen lacerum is closed with dense fibrous connective tissue and only a few small vessels pass through this foramen from the cavity of the skull to the exterior base of the skull. The main portion contains the internal carotid artery (and internal carotid plexus, deep petrosal nerve) and greater (superficial) petrosal nerve of CN VII. Inferior and anterior the foramen lacerum is continuous with the pterygoid canal.
Located in the occipital bone. Contains the spinal cord and meninges, spinal portion of the accessory nerve (CN XI), right and left vertebral arteries, anterior and posterior spinal arteries, tectorial membrane and apical ligament of the odontoid process of the axis.
Located in the greater wing of the sphenoid bone. Contains the mandibular nerve (V3) lesser (superficial) petrosal nerve and accessory meningeal vessels.
Located in the greater wing of the sphenoid bone. Contains V2.
Located in the greater wing of the sphenoid bone. Contains the middle meningeal artery and vein, and a meningeal branch of the mandibular nerve (a recurrent sensory branch from V3 passing upward from the infratemporal fossa to innervate the cranial dura).
Located between the maxilla and the palatine bone at the posterior lateral border of the hard palate. Contains the greater (anterior) palatine nerve, greater palatine artery (know up to this point as the descending palatine artery) and corresponding veins.
Hiatus for the Greater Petrosal Nerve
Located in the tegmen tympani (roof of middle ear) of the petrous temporal bone, in front of the arcuate eminence. Contains the greater (superficial) petrosal nerve of CN VII.
Hiatus for the Lesser Petrosal Nerve
Located in the tegmen tympani of the petrous temporal bone, about 3 mm anterolateral to the hiatus for the greater petrosal nerve. Contains the lesser (superficial) petrosal nerve of CN IX.
Located in the occipital bone above the anterior part of the occipital condyle. Contains the hypoglossal nerve (CN XII) and posterior meningeal branch of the ascending pharyngeal artery. Also known as the anterior condylar canal.
Incisive Foramen and Canals
Located in the maxillary bone. The foramen is located in the anterior region of the hard palate, immediately behind the incisor teeth. The incisive canals are usually visible within the incisive foramen. This complex contains the nasopalatine nerve (branch of V2) and distal branches of the septal artery (from sphenopalatine artery) which descend on the vomer (bone) of the nasal septum, as well as the greater palatine nerves and vessels (traveling from the hard palate, below).
Inferior Orbital Fissure
Located between the greater wing of the sphenoid bone and maxilla. Contains the maxillary nerve (V2), branches from the pterygopalatine ganglion to the lacrimal gland, superior alveolar nerves (anterior and middle), infra-orbital artery and vein and inferior ophthalmic vein.
Located on the anterior orbital surface of the maxilla. Contains the infra-orbital nerve, artery and vein.
Located at the anterior opening of the infra-orbital canal, in the maxilla below the infra-orbital margin. Contains the infra-orbital nerve, artery and vein (supplies portion of the mid-face).
Internal Acoustic Meatus
Located in the posterior medial surface of the petrous temporal bone. Contains the facial nerve (CN VII), vestibulocochlear nerve (CN VIII), and labyrinthine (auditory) artery (commonly from AICA but can originate from the basilar artery, superior cerebellar artery or less often PICA).
Located between the petrous temporal and occipital bone. Contains the glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), sigmoid sinus, inferior petrosal sinus, and meningeal branches of the occipital and ascending pharyngeal arteries.
Lesser Palatine Foramen
Located in the posterior inferior aspect of the palatine bone. Contains the lesser palatine nerve and vessels which in part, supply the soft palate.
Located posterior to mastoid part of the temporal bone. Contains emissary vein linking occipital vein with sigmoid sinus.
Located in the sphenoid bone between the body and root of the lesser wing. Contains the optic nerve and ophthalmic artery. Most consider the foramen and canal as synonymous terms, yet another perspective is the optic foramen is the posterior opening to the optic canal portion.
Located in the temporal bone (specifically between tympanic part of the temporal bone and tegmen tympani). Contains the chorda tympani nerve and anterior tympanic artery (a branch from the maxillary artery)
Posterior Ethmoidal Foramen
Located approximately 1-2cm behind the anterior ethmoidal foramen, in or near the frontoethmoidal suture. Contains the posterior ethmoidal nerve and vessels.
9 Posterior Superior Alveolar Canal
Located in the posterior center of the infratemporal surface of the maxilla. Contains the posterior superior alveolar nerves (V2) and vessels (from maxillary artery/vein).
Located at the root of the pterygoid processes of the sphenoid bone in line with the medial pterygoid plate. Contains the nerve in the pterygoid canal (also known as the Vidian nerve). It is formed by the joining of the greater petrosal nerve (parasympathetic branch from the facial nerve) and deep petrosal nerve (sympathetic branch from the carotid plexus).
Pterygopalatine Foramen (Sphenopalatine Foramen)
Located at the upper end of the perpendicular plate of the palatine bone between its orbital and sphenoid processes. The foramen is located in the medial wall of the pterygopalatine fossa, and in the lateral wall of the nasal cavity. Contains the sphenopalatine artery and lateral, posterior superior nasal branches of V2.
Pterygopalatine Fossa (Sphenopalatine Fossa)
Is a large pyramidal space behind and below the apex of the orbit. It communicates laterally with the infratemporal fossa through the pterygomaxillary fissure, medially with the nasal cavity through the sphenopalatine (or pterygopalatine) foramen, posteriorly with the cranial cavity through the foramen rotundum, and anteriorly with the orbit through the inferior orbital fissure. It transmits branches of the maxillary nerve (V2), facial nerve and carotid plexus (nerve in the pterygoid canal or Vidian nerve) and maxillary vessels.
Opening between the lateral pterygoid plate of the sphenoid bone and the infratemporal (posterior) surface of the maxilla and is continuous above with the inferior orbital fissure. It transmits the maxillary artery (entering the pterygopalatine fossa), and the posterior superior alveolar nerve (a branch from V2 which leaves the pterygopalatine fossa to enter the maxilla on its infratemporal surface).
Located between the styloid process and the mastoid process of the temporal bone. Contains the facial nerve (CNVII: motor branches to muscles of facial expression; and a sensory + motor branch of VII termed the posterior auricular nerve) and the stylomastoid arterial branch of the posterior auricular artery.
Superior Orbital Fissure
Located in the sphenoid bone between the body and the greater and lesser wings. Contains the occulomotor nerve (CN III), trochlear nerve (CN IV), abducens (or abducent) nerve (CN VI). Also contains the lacrimal nerve, frontal nerve and nasociliary nerve of the trigeminal nerve (all branches of V1). Finally, contains the superior ophthalmic vein, orbital branch of the middle meningeal artery, and nerve branch (or ramus) from the internal carotid plexus (sympathetic – innervation to the orbit).
10 Superior Orbital Notch or Foramen
Located on the anterior lateral surface of the zygomatic bone (also referred to as the external surface, facial surface, or malar surface of zygomatic bone). Contains the zygomaticofacial nerve (branch of V2) and vessels.
Located in the orbital surface of the zygomatic bone (internal surface facing the orbital cavity). Contains the zygomatic branch of the maxillary nerve (branch of V2).
Located near the base of the frontal process of the zygomatic bone, specifically on the temporal surface of the zygomatic bone in the infratemporal fossa (i.e., external posterior surface of the zygomatic bone facing the infratemporal fossa). Contains the zygomtic-temporal nerve (branch of V2).
11 Introduction to the Head, Scalp and Face
I. Nerves to the Face
A. Trigeminal Nerve (cranial nerve V) -Divides into three major branches: Ophthalmic, Maxillary and Mandibular. As a note, the three branches will in turn, divide into additional branches that exit skull to supply skin with somatic sensory fibers (pain, temperature and touch receptors). One branch (Mandibular) will also supply muscles.
1. Ophthalmic Nerve - A sensory nerve which supplies orbit, face and nose. a. Lacrimal Nerve (in lateral orbit). Terminal branches supply sensation to the skin over the lateral superficial eye. b. Frontal Nerve (in midline of orbit). Supplies sensation to the forehead and front of the scalp (via terminal branches of the supraorbital and supratrochlear nerves). c. Nasociliary Nerve (in medial orbit) - Supplies sensation to the tip of nose (via terminal branches of the anterior ethmoidal nerve) and the skin over the superior medial aspect of the nose (via terminal branches of the infratrochlear nerve). Posterior ethmoidal nerve also branches from nasociliary nerve to supply the posterior superior nasal cavity nasal sphenoid sinus.
2. Maxillary Nerve - A sensory nerve which supplies tissues associated with maxillary bone. Divides into several branches to the face: a. Infraorbital Nerve - Supplies sensation to upper lip, lower lid, upper cheek, and lateral nose. b. Zygomaticotemporal Nerve – Supplies sensation to skin over anterior part of temporal fossa. c. Zygomaticofacial Nerve – Supplies sensation to skin over zygomatic bone (cheek).
3. Mandibular Nerve – A sensory and motor nerve which supplies tissues associated with the mandible. The motor part innervates the muscles of mastication (i.e. muscles associated with chewing). Divides into several major branches: a. Buccal Nerve (some refer to this as the long buccal nerve) - Supplies sensation to skin over cheek (i.e., over buccinator muscle). b. Auriculotemporal Nerve-Supplies sensation to parts of the ear and skin over temporal region. c. Inferior Alveolar Nerve - Enters mandible to supply sensation to the teeth. The nerve passes through mental foramen to form the Mental Nerve (see below). d. Nerve to the Mylohyoid – Motor branch that innervates the mylohyoid muscle and anterior belly of the digastric muscle. e. Lingual Nerve - Supplies the anterior 2/3’s of the tongue and floor of the mouth with sensory fibers. f. Mental Nerve- Supplies skin over the chin and lower mandible. Represents the terminal part of the inferior alveolar nerve. g. Motor Nerves to Muscles – Temporalis, masseter, medial pterygoid, lateral pterygoid, mylohyoid, anterior belly of digastric, tensor palatini and tensor tympani muscles.
12 B. Facial Nerve (Cranial Nerve VII) - A motor nerve to the muscles of facial expression which include the muscles directly over the facial skeleton, as well as the platysma muscle (neck), occipitofrontalis muscle (back of scalp) and external auricular (ear) muscles. The nerve emerges from the stylomastoid foramen and divides into 5 general branches that are purely motor: 1. Temporal 2. Zygomatic 3. Buccal (Do not confuse with the buccal branch of the trigeminal which is sensory!) 4. Marginal Mandibular 5. Cervical
Mnemonic: To Zanzibar By Motor Car (Please – posterior auricular n)
Note, another branch of facial nerve arising from stylomastoid foramen courses posteriorly as the posterior auricular nerve which innervates occipital belly of occipitofrontalis muscle. This nerve also contains sensory fibers to external ear and skin posterior to ear. There is also a short motor nerve of the facial nerve to the stylohyoid muscle and posterior belly of the digastric muscle.
II. Major Arteries to the Face
A. Facial Artery – Main artery of the face (including lip and nose). It is a branch of the external carotid system. Gives rise to inferior labial and superior labial branches and continues upward running along the lateral part of the nose and eventually to the medial angle of the eye. Along the lateral part of the nose it is called the angular artery.
B. Superficial Temporal Artery- One of the two terminal branches of the external carotid artery (the other is the maxillary). Supplies temporal region (over squamous [smooth] part of temporal bone and scalp).
C Transverse Facial Artery- Small artery that arises from the superficial temporal artery and passes under the zygomatic arch to lateral angle of eye.
III. Major Veins of the Face
A. Facial Vein - Courses posterior to facial artery and empties into the internal jugular vein. It often sends a communicating branch to the retromandibular vein. It provides the major venous drainage of the face. (Once was commonly called anterior facial vein).
B. Superficial Temporal Vein - Drains temporal region and scalp and joins the retromandibular vein (see below).
C. Retromandibular Vein - Formed by union of superficial temporal and maxillary veins. It joins facial vein anteriorly and external jugular vein posteriorly. (Once was commonly called posterior facial vein).
IV. Lymphatic Drainage of the Face
A. The mid-face drains through lymphatic vessels that empty into the submandibular and submental lymph nodes.
B. The lateral face drains into parotid lymph nodes.
13 C. Submandibular and parotid nodes in turn drain into cervical nodes.
V. Basic Organization of the Scalp - Consists of 5 layers from superficial to deep (S-C-A-L-P).
A. Skin B. Connective Tissue C. Aponeurosis - Specifically referred to as Galea Aponurotica or Epicranial Aponeurosis. Strong membranous sheet of connective tissue that covers the dome of the calvaria from the highest nuchal line posteriorly (a bony attachment) to the eyelids anteriorly (no bony attachment). It links together the paired muscular frontal bellies (located anteriorly over the frontal bone) with the paired occipital bellies (located posteriorly over the occipital bone). Collectively the muscle is called the occipitofrontalis and is innervated by the facial nerve. D. Loose Connective Tissue- Loose, sponge-like connective tissue which permits free movement of the scalp. This is a danger area of the scalp since pus or blood can spread easily throughout the scalp. E. Pericranium - Fibrous periosteum (also connective tissue) of the skull (calvaria).
Muscles of Facial Expression
Facial nerve (CN VII) innervates all facial muscles and 3 deep muscles (stylohyoid, posterior belly of the digastric, and stapedius muscles). Muscles of the face vary in their development. The superficial fascia closely invests a number of the facial muscles. The fascia is so tightly adherent to the muscle and skin that all practical purposes, there are no potential spaces for infection within this area. (The exception is around the eyes where the fascia is not tightly adherent). The nerves generally enter the muscles on deep surfaces and typically do so close to the posterior border of the muscle. In general, the muscles of facial expression originate from bone and insert into skin (exceptions are platysma, risorius and procerus). The terminal fibers of the muscles that insert into the skin often interdigitate with fibers of other adjacent muscles of facial expression. The facial artery lies deep to the platysma, risorius, and the zygomaticus major and minor, but crosses superficial to the buccinator and the levator anguli oris. SMAS – Superficial Muscular Aponeurotic System- plane of tissue in face/neck containing facial muscle fibers, and elsewhere fibrous or fibro-aponeurotic tissue. It is not directly attached to bone. (e.g., see Perkins and Waters, Facial Plast. Surg. Clin. North Am., 2014, 22:253-268; Broughton and Fyfe, Anat. Res. Int., 2013; Pessa, Anesthet. Surg. J., 2016, 36:515-526; Hwang Choi, J. Craniofac. Surg. 2018, 29:1378-1382).
The facial muscles are divided into 6 broad categories based upon region.
I – Mouth II – Nose III – Eye (orbital group) IV – Ear V – Scalp VI- Cervical (neck)
14 Facial Muscles (learn specific origins and insertions only if it is beneficial to you)
- Lower Group (depressors) - All muscles arise (or originate) from mandible and are innervated by the marginal mandibular branch of CN VII.
1. Depressor Anguli Oris Originates from the mandible and inserts on the corner of the mouth and skin. Its function is to depress the corner of the mouth. It is often well developed, the most superficial and the most lateral of the depressor group.
2. Depressor Labii Inferioris Originates from the mandible in part from under the depressor anguli. It inserts into the skin of the chin. It functions to depress the lower lip.
3. Mentals This is the deepest lying muscle of the group. It originates from the mandible. It inserts the skin of the chin. Its function is to draw the lower lip to the gingiva.
-Middle (lateral) Group
1. Risorius This is a thin and poorly defined muscle and different in that it does not arise from the bone. It arises from subcutaneous skin over the parotid and inserts on the corner of the mouth into the skin and mucosa. Like the platysma it crosses superficial to the facial vein and artery. Its function is to draw the corner of the mouth laterally and upward (similar to the zygomatic muscles). Innervated by the buccal branch of CN VII.
2. Zygomaticus Major Originates from the zygomatic bone, anterior to the zygomaticotemporal suture and passes obliquely down to insert onto the corner of the mouth where it attaches to the skin and mucosa. It is positioned superficial to the buccinator muscle and facial vessels. Innervated by the zygomatic and buccal branches of CN VII.
3. Zygomaticus Minor Originates from the zygomatic bone posterior to the zygomaticomaxillary suture. It passes downward and medially to insert into the muscular substance of the upper lip. The action of the zygomaticus major and minor is to draw the angle of the mouth upwards and laterally. Innervated by the buccal branch (and possibly the zygomatic branch in some cases) of CN VII.
Upper Group (levators) – All muscles innervated by the buccal branch of CN VII
1. Levator Labii Superioris Alaeque Nasi Originates from the frontal process of the maxilla lateral to the nose. It inserts into the skin and alar cartilage of the nose but primarily into the skin of the upper lip. Its primary action is to raise and evert the upper lip.
15 2. Levator Labii Superioris It originates from the infraorbital margin of the maxilla, under the orbicularis oculi. It inserts into the orbicularis oris muscle and into the skin along the lateral half of the upper lip. Its action is to raise and evert the upper lip
3. Levator Anguli Oris Originates from the canine fossa of the maxilla. It attaches to the corner of the mouth and skin. Its action is to raise the angle of the mouth.
Other muscles of the mouth
1. Orbicularis Oris This muscle is made up of several strata which surround the orifice of the mouth but have different directions. It consists partly of fibers derived from the other facial muscles which pass into the lips, and the circumferential fibers proper . The orbicularis oris in its ordinary action affects the direct closure of the lips. By its deep and oblique fibers it compresses the lip against the teeth. The superficial part, consisting principally of the decussating fibers, brings the lips together and protrudes them. Innervated by the buccal branch of CN VII.
2. Buccinator Posteriorly originates from the lateral posterior alveolar processes of the maxilla and mandible and from the pterygomandibular ligament (will discuss this ligament in more detail with the pharynx). The buccinator inserts into and becomes continuous with the orbicularis oris at the lateral angle of the mouth. Noteworthy is that the parotid duct passes laterally and eventually pierces the buccinator muscle adjacent to the second upper molar on its course to enter the oral cavity. In general, the buccinator forms the substance of the soft cheek. Its function is to hold the cheek against the teeth during chewing and to keep the cheeks close against the teeth when forcefully exhaling. Innervated by the buccal branch of CN VII.
II. Nose - All muscles innervated by the buccal branches of CN VII
1. Depressor Septi Originates from the incisive fossa of the maxilla and inserts into the moveable septum. It function is to dilate the nasal opening.
2. Nasalis It is composed of 2 parts: a transverse part and an alar part. The transverse part arises from the maxilla lateral to the nasal notch. The fibers proceed upward and medially into a thin aponeurosis, which is continuous on the bridge of the nose with that of the same muscle of the opposite side, and with the aponeurosis of the procerus. The alar part arises from the maxilla, below and medial to the transverse part. It inserts into the lower lateral cartilage. Its function is to dilate the nose.
3. Procerus Originates from the fascia overlying the bridge of the nose. It inserts into the frontalis muscle. Its action is to assist the frontalis and aids in the reduction of the glare from bright light.
1. Orbicularis Oculi
16 Is divided into 3 portions: 1) an orbital portion (circular fibers around the orbital rim); 2) a palpebral portion (fibers lying in the region of the eye lid) and; 3) a pars lacrimalis portion (fibers which form a slip of muscle that attaches to the lacrimal crest behind the lacrimal sac – will cover when discussing organization of the superficial eye). The orbital portion arises from the medial palpebral ligament, nasal part of the frontal bone and frontal process of the maxilla. It forms a fairly broad ring with some circular fibers. The palpebral portion arises largely from the medial palpebral ligament but also in part from the posterior lacrimal crest. The fibers interdigitate along the lateral palpebral raphe. The vessels of the superficial eye region lie deep in this muscle. The pars lacrimalis will be discussed in detail when the orbit is dissected. Innervated primarily by the temporal and zygomatic branches of CN VII. Action is to close the eyelids. The palpebral portion acts involuntarily, closing the lids gently (sleep or blink), the orbital portion is involved with conscious (voluntary) control of eyelid closure.
2. Corrugator Supercilii Originates from the medial frontal bone and inserts into the surface of the skin above the middle of the supra-orbital margin. Its function is to draw the eyebrow medially and downwards. Innervated by the temporal branch of CN VII.
Extrinsic Muscles of the Ear
1. Anterior auricular muscle – innervated by the temporal branch of CN VII
2. Posterior auricular muscle – innervated by the posterior auricular branch of CN VII
3. Superior auricular muscle – innervated by both the temporal and posterior auricular branches of the CN VII
1. Occipitofrontalis Muscle
This is a broad muscle covering the dome of the skull. It consists of 4 parts, 2 occipital muscular bellies and 2 frontal muscular bellies that are connected by the galea aponeurotica (or epicranial aponeurosis). Posteriorly, the occipital part arises from the highest nuchal line of the occipital bone to the mastoid part of the temporal bone. Each frontal belly is attached to the galea aponeurosis (posteriorly) and inserts into the skin at about the level of the eyebrows (anteriorly). Thus, the frontalis portion has no bony attachment. The occipital part is innervated by the posterior auricular branch of CN VII and the frontal part by the temporal branch of CN VII. Draws scalp back, raises eyebrow and wrinkles forehead as in facial expression.
VI. Cervical Region (Neck)
1. Platysma Originates from the upper border of the thorax (over clavicle) and inserts into the superficial fascia at the level of the lower mandible. It lies in the superficial fascia of the neck. It is innervated by the cervical brand of CN VII. Functions to wrinkle skin of neck, assists in depressing mandible and plays a minor role in drawing coroners of mouth down and laterally.
Parotid Region, Facial Nerve and the Glossopharyngeal Nerve
I. The Parotid Gland A. General Comments: 1. Largest salivary gland that secretes saliva into the oral cavity via the parotid duct. 2. Located anterior to the auricle. 3. Roughly pyramidal in shape. 4. Encased in the parotid fascia which is an extension of the superficial layer of deep cervical fascia. Posterior thickening of the parotid fascia forms the stylomandibular ligament. 5. Superficial and deep lobes have been described. 6. The parotid duct (Stensen’s duct) emerges anteriorly from the gland, continues horizontally and passes over the masseter muscle. It then descends into the buccal fat pad to course through the buccinator muscle to the lateral wall of the oral cavity. The papilla or aperture of the duct at the oral cavity is located near the second upper (maxillary) molar. 7. A short distance above the duct, running horizontal across the face and in parallel with the duct is the transverse facial artery and vein. 8. The relationship of the parotid gland to the facial nerve constitutes the chief hazard of surgery of this gland
B. Internal contents of the parotid gland (Structures embedded in gland) 1. Facial nerve – Discussed below 2. Auriculotemporal nerve – Sensory branch of V3 that innervates the skin over the auricle, external acoustic meatus, temporomandibular joint and temporal fossa. 3. Great auricular nerve - Sensory nerve from the cervical plexus – C2 and C3. 4. External carotid artery. 5. Maxillary artery and vein. 6. Deep auricular artery and vein – A branch of the maxillary artery that supplies the external acoustic meatus. 7. Superficial temporal artery and vein 8. Transverse facial artery and vein 9. Retromandibular vein 10. Parotid lymph nodes
Note: although the posterior auricular artery (a branch of the external carotid) is in close proximity to the parotid, it is usually not embedded within the parotid gland.
C. Blood supply and innervation of the parotid gland. 1. The parotid receives blood supply from arteries traversing it (see above). 2. It’s sensory (pain, temperature and touch) and secretory (autonomic [involuntary] innervation of secretory units) fibers are from the auriculotemporal nerve. However it is important to note that the sensory fibers are true trigeminal nerve fibers, whose cells of origin are located in the trigeminal ganglion. The secretory fibers are originally derived from the glossopharyngeal nerve (CN IX). The course by which the glossopharyngeal nerve fibers take to eventually join the auriculotemporal nerve is complicated and will be discussed below (see part III).
18 II. Facial Nerve A. General functions of facial nerve: 1. Sensory –Provides somatosensory sensation to skin of the external ear (via posterior auricular nerve). 2. Motor – Innervates the muscles of facial expression. 3. Special Sensory – Provides taste fibers to the anterior 2/3rds of the tongue. 4. Autonomic – Parasympathetic innervation to all the major glands of the head (submandibular, sublingual and lacrimal) except the parotid gland which is innervated by fibers originating from CN IX (glossopharyngeal nerve).
B. Course of the motor part of the facial nerve and its branches. 1. The facial nerve leaves the brainstem and enters the internal acoustic meatus and travels within the petrous portion of the temporal bone. 2. The facial nerve emerges from the petrous portion of the temporal bone through the stylomastoid foramen. 3. The nerve sends a posterior auricular branch to innervate the occipital belly of the occipitofrontalis and posterior and superior auricular muscles (also contains some sensory fibers to external ear). 4. The main (motor) branch enters the parotid gland and divides into two divisions, an upper division (temporofacial division) and lower division (cervicofacial division). 5. Branches of CN VII appear at the anterior edge of the parotid gland and radiate forward, downward and upward. The main branches which emerge from the parotid are commonly called temporal, zygomatic, buccal, marginal mandibular, and cervical nerves (To Zanzibar By Motor Car).
C. General innervation patterns of the facial nerve: 1. Cervical branch innervates the platysma. 2. Marginal mandibular branch innervates the lower (depressor) perioral group of muscles. 3. Buccal branch innervates the middle (lateral action) and upper group (levators) of the mouth as well as those muscles acting on the nose. 4. Zygomatic branch innervates the zygomatic major and orbicularis oculi. 5. Temporal branch innervates the anterior auricular, orbicularis oculi, frontal belly of the occipitofrontalis and corrugator muscles.
Note: Vertical incisions over the anterior part of the gland carry greater danger to the branches of CN VII as well as the parotid duct, while horizontal incisions render either of these unlikely.
III. Glossopharyngeal nerve (CN IX) and parasympathetic innervation of the parotid gland. A. General Functions of the glossopharyngeal nerve: 1. Sensory – Provides somatosensory sensation to skin of the ear, visceral sensation to the pharynx, posterior one-third of the tongue, and palatine tonsil. 2. Motor – innervates the stylopharyngeus muscle (a pharyngeal muscle to be dissected later). 3. Special sense – Provides taste fibers to the posterior 1/3rd of tongue. 4. Autonomic Innervation – Parasympathetic innervation of the parotid which causes secretion of parotid contents by activation of secretory units (modified myoepithelial contraction). The result is that muscle squeezes secretory cells and forces secretory product into ductule system).
19 B. Parasympathetic innervation of parotid gland 1. Preganglionic parasympathetic cell bodies in the brain stem give rise to the preganglionic parasympathetic fibers that form a component of CN IX. 2. CN IX (and the preganglionic parasympathetic fibers) exits the cranial cavity through the jugular foramen. 3. CN IX gives rise to the tympanic nerve (which contains the preganglionic parasympathetic fibers) which enters the middle ear through the tympanic canaliculus (a foramen between the jugular foramen and carotid canal). 4. The tympanic nerve changes name to the lesser petrosal nerve which leaves the middle ear to enter the middle cranial fossa through the hiatus for the lesser petrosal nerve (thus, the lesser petrosal nerve contains the preganglionic parasympathetic fibers originating from CN IX). 5. The lesser petrosal nerve exits the middle cranial fossa by traversing the foramen ovale to enter the infratemporal fossa (fossa located below the zygomatic arch). 6. In the infratemporal fossa is the Otic Ganglion. Preganglionic parasympathetic fibers from the lesser petrosal nerve terminate on postganglionic parasympathetic cell bodies in the Otic ganglion. 7. Postganglionic parasympathetic cell bodies in the Otic Ganglion give rise to postganglionic parasympathetic fibers which finally join the auriculotemporal nerve (a nerve of the trigeminal system). The auriculotemporal nerve passes through the parotid gland to deliver parasympathetic fibers to innervate the secretory component of the gland.
IV. Sympathetic innervation of parotid gland. A. Basic concepts and general function of sympathetic innervation. 1. Regulate diameter of blood vessels and therefore, influence blood flow. 2. In general preganglionic sympathetic nerve fibers to the head arise from cell bodies in the thoracic spinal cord. The fibers travel upward in the neck, and within sympathetic chain, to terminate on postganglionic sympathetic cell bodies located in the superior cervical ganglion. 3. Postganglionic cell bodies in the superior cervical ganglion give rise to postganglionic sympathetic fibers that travel on the major blood vessels (internal and external carotid arteries) to get to their target tissues.
B. Specific pathway of sympathetic innervation of parotid gland.
Preganglionic sympathetic nerve fibers arise from cell bodies in the thoracic spinal cord. The fibers travel upward in the sympathetic chain and terminate on cell bodies in the superior cervical ganglion. Cell bodies in the superior cervical ganglion give rise to postganglionic sympathetic fibers that join the external carotid artery, travel to the maxillary artery (branch of the maxillary artery) then finally join the auriculotemporal nerve (of the trigeminal system) to innervate the parotid blood vessels.
20 Superficial Eye and Orbital Contents
SUPERFICIAL EYE CONTENTS (and some orbital relationships)
I. Both lids are similar in construction
II. External landmarks include: A Palpebral fissure. B. Palpebral fold. C. Lateral canthus – rests on sclera. D. Medial canthus – not on sclera. 1. Forms the lacrimal lake. 2. Plica semilunaris – thought to be a vestige of the moveable 3rd lid. 3. Lacrimal caruncle - large modified sweat and sebaceous glands. E. Eyelashes (Cilia) - -arranged in 2-3 rows from lateral canthus to plica semilunaris. F. Associated with the cilia are: 1. Sebaceous glands. 2. Rudimentary sweat glands. 3. Stye – a result from blockage of either duct type. G. Lacrimal papilla – located at level of plica semilunaris. 1. Located within each lid is an opening called the lacrimal punctum. a. Origin of lacrimal canaliculi which drain tears from lacrimal lake. H. Yellow lines along posterior edge of free margin of eye lids (i.e., rim of eyelids) represent opening of tarsal glands of Meibomian. Blockage of this gland results in a chalazion. I. Conjunctiva - lines the inside of the eyelids and covers the sclera (white of the eye). It is composed in part, epithelium and assists in lubricating the eye by producing mucous and tears. Also serves an immune function preventing microbes from entering the eye.
III. Orbicularis Oculi A. Thin in the lids. B. Attached medially to the medial palpebral ligament. C. Attached laterally to the lateral palpebral raphe (not the lateral palpebral ligament). D. A small amount of muscle emerges from orbicularis oculi body which attaches to the posterior lacrimal crest. This is known as the pars lacrimalis muscle, or muscle of Horner, and will be discussed further under the lacrimal apparatus heading (see below).
IV. Orbital Septum A. Fascia that extends into upper and lower lids. B. Continuous with periorbita and periosteum of skull. C. Originates from the orbital rim of bone and forms a continuous membrane. D. In upper lid blends with the aponeurosis of the levator palpebrae superioris. E. Medially extends down to posterior lacrimal crest behind pars lacrimalis – excluding the lacrimal sac from the orbital contents. F. The orbital septum forms a weak barrier between the lid and orbital contents.
V. Tarsal Plates A. Dense connective tissue that contains sebaceous (oily) glands (of Meibomian). B. Main support for the lids.
21 VI. Medial Palpebral Ligament A. Anchors the tarsal plates medially to the frontal process of the maxilla and the anterior lacrimal crest. B. Important landmark for identifying the lacrimal sac (which lies behind the ligament). C. Lower border is better developed.
VII. Lateral Palpebral Ligament A. Ligament is frequently confused with the lateral palpebral raphe with is merely an interlacing of muscle fibers of the orbicularis oculi. B. The ligament is completely separate from the raphe. C. It lies behind the orbital septum. D. Attaches medially to the tarsal plates and laterally to the zygomatic bone at the orbital tubercle and much less distinct than medial palpebral ligament.
VIII. Levator Palpebrae Superioris Muscle (LPSM) A. Upper lid contains the LPSM in addition to the tarsal plate and orbital septum. B. Muscle originates from boney orbital roof/lesser wing of sphenoid bone. C. Muscle body lies between the roof and the superior rectus and is innervated by CN III. D. Aponeurosis (anterior to muscle body) descends behind the orbital septum and inserts into the orbital septum, tarsal plate and skin of the upper eyelid. E. Muscle supports the superior palpebral fold that disappears with its paralysis (ptosis). F. Aponeurosis is much wider than the muscle. 1. The lateral cornu (or horn) divides the lacrimal gland into thin palpebral and thick orbital portions. 2. Attaches to the orbital tubercle where the lateral palpebral ligament also attaches. 3. The weaker medial cornu (or horn) blends into the orbital septum at the level of the posterior lacrimal crest. G. Superior Tarsal Muscle (or superior palpebral muscle of Müller). 1. Thin sheet of smooth muscle. 2. Attached to the inferior surface of levator palpebrae superioris (LPSM) muscle. 3. Inserts into the superior border of superior tarsal plate. 4. Distinct from LPSM in that it is smooth muscle and is innervated by sympathetic, autonomic nerve fibers from cells in the superior cervical ganglion. 5. Paralysis of Müller’s muscle (Horner’s syndrome) leads to ptosis (drooping) of the upper eye lid.
IX. Conjunctiva A. Forms posterior surface of the eye lids then extends onto the anterior surface of the globe. B. Space between the lid and the globe is termed the fornix.
X. Innervation of Lids (Review) A. Temporal and zygomatic branches of facial nerve (CN VII) enter the orbicularis oculi near the lateral palpebral raphe and on the inferior surface of the muscle providing motor innervation. B. Upper lid is also innervated by : 1. Oculomotor nerve (CN III) – innervates the levator palpebrae superioris muscle. 2. Sympathetic nerves (from the superior cervical sympathetic ganglion) – innervate the superior tarsal muscle (Müller’s muscle). C. Paralysis of either levator palpebrae superioris and superior tarsal muscle give ptosis. Ptosis is an abnormally low (drooping) upper eyelid.
22 D. Only with paralysis of the LPSM is there the loss of superior palpebral fold. E. Cutaneous innervation is via V1 (supratrochlear, supraorbital, lacrimal and infratrochlear nerves to upper lid) and V2 (infraorbital nerve to lower lid).
XI. Major Arteries of Eyelids: A. Inferior Medial – Angular branch of the facial artery. B. Inferior Lateral –Transverse facial artery. C. Superior Lateral – Superficial temporal artery. D. Superior Medial – Supraorbital artery (branch of the ophthalmic artery).
XII. Veins – larger and less constant. A. Inferior Medial – Angular branch of the facial vein. B. Inferior Lateral – Transverse facial vein. C. Superior Lateral– Superficial temporal vein. D. Superior Medial- Supraorbital vein (branch of superior ophthalmic vein).
XIII. Lacrimal Apparatus A Lacrimal Gland: 1. Divided into 2 portions by the lateral portion of the levator palpebrae superioris. a. Orbital portion (larger). b. Palpebral portion. 1) 6-12 lacrimal ducts emerge from palpebrae portion. B. Lacrimal Vessels: 1. Lacrimal artery (via ophthalmic artery). C. Lacrimal Drainage: 1. Movement of the lids distributes excess tears to lacrimal lake (medially). 2. Lacrimal canaliculi (ducts) originate at lacrimal punctum and drain into lacrimal sac. 3. Lacrimal sac: a. Lies behind medial palpebral ligament and partly surrounded by pars lacrimalis (Horner’s muscle). b. Lacrimal sac lies in lacrimal fossa between anterior and posterior lacrimal crest and posterior to the medial palpebral ligament as noted above. 4. Lacrimal pump: a. Tension (pull) on the sac by pars lacrimalis muscle produces negative pressure in the sac. E. Lacrimal Duct: 1. Always a narrowing of the passage at the junction of the sac and duct. 2. Duct terminates by eventing the nasal mucosa at the inferior nasal meatus.
XIV. Bony Orbit A. Roof: 1. Orbital part of the frontal bone. 2. Lesser wing of sphenoid bone. B. Lateral Wall: 1. Greater wing of sphenoid bone. 2. Zygomatic bone. C. Floor: 1. Zygomatic bone.
23 2. Maxilla. 3. Orbital process of palatine bone. D. Medial Wall: 1. Frontal process of maxilla. 2. Lacrimal bone. 3. Orbital plate of ethmoid bone (lamina papyracea). 4. Body of sphenoid bone.
XV. Orbital Fissures and Foramen A. Superior orbital fissure- Contents: 1. Trochlear, lacrimal, frontal and nasociliary nerves (CN V1 nerve branches) 2. Upper and lower divisions of oculomotor nerve (CN III). 3. Abducens (or abducent) nerve (CN VI). 4. Superior ophthalmic vein (drains into cavernous sinus of middle cranial fossa). B. Inferior orbital fissure- Contents: 1. Infraorbital nerve (V2 nerve branch). 2. Inferior ophthalmic vein (drains into the pterygoid plexus of infratemporal fossa). C. Anterior and Posterior Ethmoidal Foramina: 1. Contains anterior and posterior ethmoidal nerves, arteries and veins respectively. D. Optic Canal: 1. Contains optic nerve and ophthalmic artery.
XVI. Orbital Fascia: A. Periorbita 1. Periosteum - but within orbit. 2. Less firmly attached – allows for abscess formation. 3. Continuous with periosteum proper of skull. 4. Forms orbital septum of lid (curtain like extension, or septa). 5. Thickened posteriorly to form annular tendon of Zinn. a. Common attachment of the 4 rectus muscles.
XVII. Bulbar Sheath (Tenon’s capsule – posterior surface of globe) A. Thin membrane which envelops the eyeball from the optic nerve to the limbus, separating it from the orbital fat and forming a socket in which it moves. B. Pierced by the orbital muscles. C. Pierced by ciliary nerves and vessels. D. Bulbar sheath thickens to form: 1. Suspensory ligament of Lockwood – Attaches to the periosteum by the check ligament which are continuous with lateral rectus and medial rectus, encompasses the inferior rectus and inferior oblique and is a hammock-like part of the bulbar sheath strongly attached to the orbital wall thus supports the eyeball. 2. Medial check ligament – Broad sheet of fascia attaching the medial rectus to orbital wall just posterior to posterior lacrimal crest, anteriorly fused with medial horn of levator palpebrae superioris muscle. 3. Lateral check ligament – stronger than medial check ligament, is an expansion from lateral surface of lateral rectus at marginal (orbital) tubercle of zygomatic bone, fuses with lateral horn of levator muscle. 4. One major function of check ligaments is to prevent retropulsion of globe.
24 XVIII. Motor Nerves of the Orbit A. All 3 motor nerves (CN’s III, IV and VI) enter through the superior orbital fissure. 1. Oculomotor (CN III) and abducens (CN VI) nerve enter through the oculomotor foramen (annular tendon of Zinn) and therefore lie within the muscle cone. 2. Trochlear (CN IV) enters above the ring and never included within the muscle cone. 3. Trochlear and abducens nerve supply only 1 muscle. 4. Oculomotor supplies the remainder (including the LPSM). B. Oculomotor Nerve (CN III) 1. Courses between the posterior cerebral and superior cerebellar arteries. 2. Penetrates dura just lateral to posterior clinoid process to enter lateral wall of cavernous sinus. 3. At anterior part of cavernous sinus divides into 2 main subdivisions (superior and inferior). 4. Superior division innervates: a. Levator palpebrae superioris. b. Superior rectus. 5. Inferior division innervates: a. Medial rectus. b. Inferior rectus. c. Inferior oblique. d. Ciliary ganglion – parasympathetic fibers of the oculomotor nerve which innervate the sphincter and ciliary smooth muscles. C. Trochlear Nerve (CN VI) 1. Supplies superior oblique muscle. 2. Penetrates dura near posterior clinoid process to enter the lateral wall of the cavernous sinus. D. Abducens Nerve (CN VI) 1. Supplies the lateral rectus muscle. 2. Penetrates dura on clivus in posterior cranial fossa. Ascends on the deep surface of dura to the posterior clinoid process region and passes over the petrous tip and into Dorello’s canal (opening in cavernous sinus for Abducens nerve and inferior petrosal sinus). The canal is in part formed by the petrosphenoidal (Gruber’s) ligament and posterior clinoid process. 3. Lies against the lateral wall of internal carotid (only cranial nerve to be within the cavernous sinus as the rest are embedded in the dura that forms lateral wall of cavernous sinus). 4. Can be injured at several points a. At sharp turn over the petrous tip cells. b. Cerebellar abscesses frequently cause paralysis.
XIX. Sensory Nerves (pain, temperature touch) of the Orbit A. Frontal nerve of V1 divides to give rise to the supraorbital and supratrochlear nerves. B. Lacrimal nerve of V1. C. Nasociliary nerve of V1 gives rise to short and long ciliary nerves (supply globe), posterior and anterior ethmoidal nerves (supply nasal cavity and sinuses) and infratrochlear nerve (supply skin below inferior orbital margin). D. Infraorbital nerve of V2.
XX. Autonomic Innervation of Eye. A. Ciliary Ganglion- parasympathetic ganglion only (sensory fibers pass through).
25 B. Lies between the optic nerve and lateral rectus adjacent to the ophthalmic artery. C. Ciliary ganglion receives a contribution from 3 incoming nerves: 1. Sensory fibers from nasociliary nerve (branch of V1.). a. Fibers pass through the ganglion to form part of the short ciliary nerves. 2. Parasympathetic motor fibers from CN III (innervate smooth muscle). a. Preganglionic fibers arising from nucleus of Edinger-Westphal. b. Course with the branch going to the inferior oblique muscle. c. These nerves enter and synapse on cell bodies within the ganglion. d. Postganglionic parasympathetic fibers leave the ganglion and join the short ciliary nerves (of trigeminal nerve origin). e. Distributed to the sphincter muscle of the pupil and ciliary muscle. 3. Sympathetic ramus fibers. a. Preganglionic sympathetic fibers from the thoracic spinal cord ascend in sympathetic chain and end by synapsing in the superior cervical ganglion. b. Postganglionic sympathetic fibers from the superior cervical ganglion run on the internal carotid artery (internal carotid plexus) and branch in the cavernous sinus to form the sympathetic ramus. c. Sympathetic ramus enters the oculomotor foramen (formed by the annular tendon of Zinn) then pass through the ciliary ganglion to join the short and long ciliary nerves. e. Distributed to dilator muscle of pupil, ciliary muscle and blood vessels. 4. Summary of nerves leaving (emerge from) the Ciliary ganglion: a. Short Ciliary nerves extend from the ganglion and contain sensory, sympathetic and para-sympathetic nerve fibers. b. Long Ciliary nerves extend from the ganglion and contain sensory and sympathetic nerves fibers.
XXI. Summary of Arteries of Orbit 1. Ophthalmic Artery and branches: a. Central artery of retina. b. Ciliary arteries. c. Lacrimal artery. d. Supraorbital artery. e. Posterior and anterior ethmoidal arteries. f. Dorsal nasal artery. g Supratrochlear artery.
XXII. Summary of Veins of Orbit 1. Superior Ophthalmic Vein (drains into cavernous sinus via superior orbital fissure). 2. Inferior Ophthalmic Vein (drains into cavernous sinus and pterygoid plexus via inferior orbital fissure).
XXIII. Muscles of Orbit (LR6SO4)3. [4 recti, 2 oblique, 1 levator] 1. Superior Rectus 2. Inferior Rectus. 3. Lateral Rectus. 4. Medial Rectus. 5. Superior Oblique. 6. Inferior Oblique. 7. Levator Palpebrae Superioris.
26 Triangles of the Neck I. Anterior Triangle of the Neck
Boundaries: Superior: Mandible Posterior: Sternocleidomastoid (SCM) muscle Midline: Median plane Inferior: Sternum
A. Muscular Triangle - Borders Superior: Hyoid bone Inferior-lateral: Sternocleidomastoid muscle Superior-lateral: Superior (or anterior) belly of omohyoid muscle Midline: Median plane Floor: Sternothyroid and thyrohyoid muscles Inferior: Sternum and clavicle
Muscular Triangle – Contents: Muscles: (2 layers, named according to inferior and superior connective tissue attachments) Sternohyoid muscle – from sternum and first rib to the hyoid bone. Omohyoid muscle – from suprascapular ligament of scapula to the body and greater horn of hyoid bone (omos = shoulder). The intermediate tendon is attached to the posterior surface of the SCM. Sternothyroid muscle – from sternum and first rib to the oblique line of the lateral surface of the thyroid cartilage. Thyrohyoid muscle – (upward continuation of sternothyroid muscle ) from oblique line of thyroid cartilage to grater horn of hyoid bone.
General Function of the infrahyoid muscles: 1) Fix the hyoid bone to stabilize the base of the tongue (via action on hyoglossus muscle). 2) Draws the larynx to hyoid bone early in swallowing phase. 3) Draws the larynx down with the fixed hyoid in late swallowing phase.
Major Structures in Muscular Triangle (located in the floor of muscular triangle): Thyroid gland and frequent pyramidal lobe. Thyroid cartilage and enclosed larynx – Respiratory, vocalization system. Trachea – Respiratory system (inferior continuation of larynx). Esophagus – Digestive System (inferior continuation of pharynx).
Nerves of Muscular Triangle: Ansa cervicalis nerve – Motor nerve to hyoid muscles of muscular triangle. Originates from cervical spinal cord. Specifically, consists of ventral rami of C2 and C3 (inferior root) and from C1 (superior root) of which latter temporarily runs with the hypoglossal nerve.
27 Collectively the superior and inferior roots form a “loop” (ansa = any structure in the form of a loop or arc).
note: The nerve to thyrohyoid (originates from C1) courses anteriorly in the hypoglossal nerve sheath then “drops off” the hypoglossal nerve to innervate the thyrohyoid muscle then geniohyoid muscle. General rule: All muscles with “hyoid” in the name are innervated by ansa cervicalis (C1-C3) except the stylohyoid (facial nerve-cranial nerve VII), mylohyoid (trigeminal nerve-cranial nerve V) and hyoglossus (hypoglossal nerve-cranial nerve XII).
Internal and external laryngeal nerves – Both are branches of the vagus nerve (CN X). The internal laryngeal nerve provides sensory innervation to the larynx (above level of vocal cord) and the external laryngeal nerve provides motor innervation to the cricothyroid muscle and inferior constrictor muscle.
Recurrent laryngeal nerve – Branch of the vagus nerve (CN X). Provides sensory innervation to larynx (below level of vocal cord) and motor to all intrinsic laryngeal muscles except the cricothyroid muscle.
Vascular Structures of Muscular Triangle: Superior and inferior thyroid arteries – Superior thyroid artery is branch of the external carotid arterial system and the inferior thyroid artery is branch of subclavian arterial system (via thyrocervical trunk). The superior thyroid artery is commonly accompanied by the external laryngeal nerve.
Located below (e.g., deep to) the infrahyoid muscles and arches across the trachea and esophagus and is invested in a fibrous capsule. The thyroid gland is an endocrine gland which produces thyroxin, an important compound for controlling the metabolic rate (oxidation) of the body. Upper parts of the lobes are molded against the cricoid and thyroid cartilages. Pretracheal layer of fascia (also known as the visceral fascia) is attached anteriorly, laterally and posteriorly. Thus, encircling the trachea, esophagus and thyroid gland. This forms the visceral compartment (or visceral space). Blood supply is rich and arises from the paired superior thyroid arteries (from external carotid system) and inferior thyroid arteries (from subclavian arterial system). An unpaired and variable thyroidea ima artery (10% of cases) may arise from the brachiocephalic artery or from the arch of the aorta. When present it ascends on the ventral surface of the trachea which it supplies, and distributes to the isthmus (midline) of the gland. Veins are variable, but always include superior and inferior thyroid veins and usually a middle thyroid vein as well. The superior thyroid artery accompanies the external laryngeal nerve. The inferior thyroid nerve accompanies the recurrent laryngeal nerve. Nerves to the thyroid gland are postganglionic sympathetic fibers from the middle cervical ganglion (vasomotor to follicles of the gland).
28 Parathyroid Glands
Two to six, flattened, oval bodies lying against the dorsum of the thyroid gland. Located under the sheath of the thyroid but have their own capsule as well. Have only a spatial relationship to the gland as they are their own microscopic structure and endocrine function. Produces the hormone parathormone (or parathyroid hormone) which regulates and maintains the normal metabolic relationship between the blood and skeletal calcium. Also regulates phosphorus metabolism. Blood supply arises from the superior and inferior thyroid arteries. Nerve supply is abundant and arises from the cervical sympathetic ganglia of sympathetic chain.
B. Carotid Triangle - Borders Posterior: Sternocleidomastoid (SCM) muscle Superior: Posterior belly of digastric muscle Anterior (Midline): Superior belly of omohyoid muscle Floor: Thyrohyoid, hyoglossus, middle and superior constrictor muscles
Carotid Triangle - Contents Nerves of Carotid Triangle: Ansa cervicalis nerve (C1-C3) superior and inferior roots. Internal and external laryngeal nerves of Vagus. Cranial nerve X (Vagus nerve) in carotid sheath. Cranial nerve XI (Spinal Accessory nerve) – innervates the SCM and trapezius. Cranial nerve XII (Hypoglossal nerve)- innervates all tongue muscles (muscles whose name ends with the suffix “glossus” ) except the palatoglossus (which is innervated by cranial nerve X). C1 nerve branch that innervates the thyrohyoid muscle and geniohyoid muscle. The cervical branch of C1 briefly travels along with (e.g., joins) cranial nerve XII.
Vascular Structures of Carotid Triangle: Common Carotid artery. Bifurcation of carotid artery (occurs at approximately the C4-C5 level). Internal carotid artery (no branches in neck). External carotid artery. Ascending pharyngeal artery – Branch of external carotid artery. Superior thyroid artery – Branch of external carotid artery. Lingual artery – Branch of external carotid artery. Occipital artery – Branch of external carotid artery. Internal jugular vein (in carotid sheath with internal carotid artery and vagus nerve). Superior thyroid vein. Lingual vein. Lymph nodes – Drain lower lip, anterior tongue and floor of mouth.
Muscles of Carotid Triangle: Thyrohyoid muscle – See muscular triangle Hyoglossus muscle – Only the very inferior part of this muscle is located in the carotid triangle. Superior and Middle Constrictor muscles – Will cover in detail during pharynx dissection.
Carotid sheath encloses 3 structures: (1) Internal jugular vein, (2) Internal carotid artery, (3) Vagus nerve (CN X).
C. Submandibular (or Digastric) Triangle - Borders Posterior-inferior: Posterior belly of digastric muscle Anterior-inferior: (Midline): Anterior belly of digastric muscle Superior: Border of mandible Floor: Mylohyoid, hyoglossus and middle constrictor muscles
Submandibular Triangle – Contents: General Structures: Tail of parotid gland Submandibular gland (covered below) Lymph nodes
Vascular Structures of Submandibular Triangle: Facial artery and vein Submental artery and vein (branches of facial artery and vein respectively)
Muscles of Submandibular Triangle:
Anterior and posterior belly of the digastric muscle – For the entire muscle, the anterior belly is attached superiorly to the mental spine (or genial tubercle) of the mandible and the posterior belly is attached inferiorly to the mastoid notch of the temporal bone. The intermediate tendon, which links the two muscular bellies, is attached to the greater horn and body of the hyoid bone. The anterior belly is innervated by the nerve to the mylohyoid f the trigeminal system and the posterior belly is innervated by a branch from the facial nerve as it emerges from the stylomastoid foramen (cranial nerve VII). This muscle depresses the mandible when the hyoid is fixed and elevates hyoid bone when the mandible is fixed during swallowing.
Stylohyoid – Superior attachment is the styloid process of the temporal bone and inferior attachment is the body of the hyoid bone. It is innervated by the facial nerve (cranial nerve VII). It elevates and retracts the hyoid bone, therefore elongates the floor of the mouth.
Mylohyoid muscle – Superior attachment is the mylohyoid line and inferior attachment is the body of the hyoid bone. Is innervated by the mylohyoid nerve of the trigeminal nerve system (i.e., CN V). Specifically, the nerve to the mylohyoid is a branch from the inferior alveolar nerve in the infratemporal fossa. The mylohyoid muscle elevates hyoid bone, floor of mouth and tongue during swallowing and speaking. When hyoid bone is “fixed” the mylohyoid muscle depresses the mandible.
Hyoglossus- It originates from the body and greater horn of the hyoid bone and inserts into the inferiolateral part of the tongue. It is innervated by the hypoglossal nerve (cranial nerve
30 XII). It depresses and retracts the tongue. General rule: all the tongue muscles whose name ends with the suffix “glossus” are innervated by cranial nerve XII except the platoglossal muscle which is innervated by cranial nerve X (the vagus). (Glossal, glossa - refers to tongue)
D. Submental Triangle - Borders Superior: Mandible Inferior: Body of hyoid bone Lateral: Anterior belly of digastric muscle Midline: midline Floor: Mylohoid muscle
Note: this is the only unpaired triangle.
Submental Triangle – Contents: Anterior jugular vein. Submental artery and vein (branches of facial artery and vein respectively). Lymph nodes. Mylohyoid muscle (see above). Anterior belly of the digastric muscle (see above).
Geniohyoid muscle – This muscle is below the floor of the submental triangle. Its superior attachment is the mental spine (or genial tubercle) of the mandible and inferior attachment is the body of the hyoid bone. (mentum = chin; genial = chin) It is innervated by fibers from C1 of the ansa cervicalis which hitch a ride on part of the hypoglossal nerve (cranial nerve XII). Elevates hyoid bone (when mandible is stabilized) and assists in depressing the mandible (when hyoid bone is stabilized).
E. Submandibular Gland
Superficial lobe lies within the digastric triangle covered by the investing layer of the deep cervical fascia. Mandibular branch of CN VII and facial vein are within this fascia. Medial to the gland is mylohyoid muscle, hyoglossus muscle, lingual artery, lingual nerve, hypoglossal nerve and deep lingual vein.
Submandibular duct (Wharton’s) is approximately 5 cm long. The duct arises superficially near the mylohyoid muscle and passes between the mylohyoid and hyoglossus muscles. Anteriorly the duct passes between sublingual gland and genioglossus muscle and opens lateral to frenulum of tongue. The large superficial lobe and smaller deep lobe are separated by the mylohyoid muscle. Will cover again in oral cavity lecture/dissection.
Note: Facial artery courses through the submandibular triangle and is usually transected twice during resection of the submandibular gland.
31 II. Posterior Triangle of the Neck
Boundaries Posterior: Trapezius muscle Anterior: SCM muscle Inferior: Clavicle Floor: Scalene Muscles (Ant., Mid. Post.), Levator Scapulae, Splenius Capitis Subdivisions: A) Occipital Triangle B) Subclavian (or Omoclavicular, Supraclavicular) Triangle
A. Occipital Triangle – borders (basically above omohyoid m.): Inferior: Posterior (or inferior) belly of omohyoid muscle Posterior-Superior: Trapezius muscle Anterior-Superior SCM muscle
B. Subclavian (supraclavicular) triangle – borders (basically below omohyoid m.): Posterior: Trapezius muscle Superior: Posterior belly of the omohyoid muscle Inferior: Clavicle Anterior: SCM muscle
C. Posterior Triangle and root of the Neck – General Contents: Nerves: Lesser occipital nerve (C2-C3) (sensory nerve). Transverse cervical nerve (C2-C3) (sensory nerve). Greater auricular nerve (C2-C3) (sensory nerve. Supraclavicular nerves (lateral, intermediate and medial branches) (C3-C4) (sensory) Cranial nerve X (Vagus Nerve) contained within the carotid sheath. Cranial Nerve XI (Spinal Accessory Nerve - innervates SCM and Trapezius muscles.). Phrenic nerve (C3, C4 C5 keeps the diaphragm alive) (motor nerve). Brachial plexus (C5-T1). Sympathetic chain (motor to visceral structures – smooth muscle in blood vessels, Müllers muscle, dilator pupillae).
Arterial System: Common carotid artery Subclavian artery and its branches which include: Vertebral artery. Internal thoracic artery. Transverse cervical artery-from thyrocervical trunk of subclavian artery. Suprascapular artery-From thyrocervical trunk of the subclavian artery. Inferior thyroid artery-From thyrocervical trunk of the subclavian artery. Costocervical trunk- A branch of the subclavian that eventually divides into deep cervical and highest intercostal arteries. Dorsal scapular artery-A branch of the subclavian artery. Occipital artery (a branch of the external carotid artery).
Venous System: External jugular vein – Opens into the subclavian vein. Subclavian vein - Unites with internal jugular to form the brachiocephalic vein. Internal jugular vein – Unites with subclavian to form the brachiocephalic vein.
32 Anterior jugular vein – Opens into either the external jugular or subclavian vein. Transverse cervical vein – Opens into the external jugular vein. Suprascapular vein – Opens into the external jugular vein. Inferior thyroid vein – Opens into the brachiocephalic vein. Vertebral vein – Opens into the brachiocephalic vein. Internal thoracic vein – Opens into the brachiocephalic vein.
Lymphatic System: Thoracic duct (on left) – Drains the entire body except the right side of the head, neck and thorax (above the diaphragm). Commonly located at the junction of the left internal jugular vein and left subclavian vein.
Right lymphatic duct (on right) - Drains the right side of the head, neck and thorax (above diaphragm). Commonly located at the junction of the right internal jugular vein and right subclavian vein.
Lymph Nodes - Superficial group of cervical lymph nodes are located in the vicinity of the external jugular vein. The superficial nodes drain into the deep nodes (deep nodes are located in the vicinity of the internal jugular vein). On the right, the deep nodes drain into the right lymphatic duct and on the left the deep nodes drain into the thoracic duct.
Muscles: Scalene muscles: (3) all arise from transverse processes of cervical vertebrae. All insert onto rib. All innervated by ventral rami of cervical plexus. All muscles flex neck laterally and elevate associated rib during forced inspiration. Anterior Scalene – Originates from transverse processes of C3-C6 and inserts on the first rib. Innervated by ventral rami of C5 – C8. This structure is the “key to the root of the neck” since many other structures assume predictable positions in relation to it and therefore helps organize the anatomy of the region. Middle Scalene – Originates from transverse processes of C2-C7 and inserts on first rib. Innervated by ventral rami of C3-C8. This is the largest of the scalene muscles. Posterior Scalene – Originates from transverse processes of C4-C6 and inserts on second rib. Innervated by ventral rami of C7-C8.
Levator Scapulae – Originates from the posterior tubercles of transverse processes of C1-C4 and inserts on superior part of medial border of scapula. Innervated by the dorsal scapular nerve (C5 of the brachial plexus). Elevates scapula.
Splenius Capitis – Originates from inferior half of ligamentum nuchae and spinous processes of superior 6 thoracic vertebrae and inserts onto the lateral part of the mastoid process (of temporal bone) and lateral third of superior nuchal line (of occipital bone). Innervated by dorsal rami of middle cervical spinal nerves. Lateral flexion of the head and neck (unilaterally) and extension of the head and neck (bilaterally).
33 III. Fascial Planes of the Neck
Superficial fascia – Lies beneath the skin, thus includes the subcutaneous tissues. Surrounds the neck and encompasses the platysma muscle, external jugular vein and cervical branch of cranial nerve VII (which innervates the platysma).
Superficial layer of deep cervical fascia – Also known as investing fascia because this fascia splits to invest the trapezius and SCM muscles. Firmly attached to hyoid, mandible and zygomatic arch. Inferiorly it splits to enclose the hyoid muscles and eventually attaches to clavicle and the acromion and spine of scapula. Invests the parotid and submandibular gland. Forms the stylomandibular ligament. The infrahyoid muscles are considered by some authorities as being invested within the superficial layer of deep cervical fascia. It is also common to name the fascia which invests the infrahyoid muscles as “the fascia of the infrahyoid muscles” (Grodinsky and Holyoke, Am. J. Anat., 1938).
Middle layer of deep cervical fascia – Also known as pretracheal or visceral fascia.
Envelopes the viscera of the neck forming visceral compartment. (i.e., pharynx, esophagus, larynx, trachea, thyroid and parathyroids). Woodburne and Burkel (Essentials of Human Anatomy) describe the visceral fascia as being composed of: 1) the “pretracheal fascia” which covers the larynx and trachea and splits to enclose and form the sheath of the thyroid and; 2) the buccopharyngeal fascia” which covers the external surface of the upper digestive tract (the pharynx and buccinator muscles). The buccopharyngeal fascia is continuous with the pretracheal fascia below. Thus, represents an upward extension of the same fascial plane.
Deep layer of deep cervical fascia – Also known as the prevertebral fascia.
Encloses the vertebral column and associated muscles. Separates vertebral muscles from the esophagus. Fascia extends from the base of the skull to the coccyx. Anteriorly, and in front of the body of the vertebrae the prevertebral fascia splits into two laminae:1) an “alar layer of fascia” (anterior laminae) which is located anteriorly and ;2) “prevertebral layer of fascia” (posterior laminae) which is located posteriorly. Between the two is the alar space. Clinically, the alar space is known as the “danger space” because it is very susceptible to abscess penetration and it extends from the base of the skull to the diaphragm. (Abscess refers to pus formation which is an inflammation product made up of leucocytes or white blood cells). Therefore, infections can spread once entering this space, from the head to the thorax.
Carotid sheath Encloses the carotid artery, internal jugular vein and vagus nerve. Fuses with prevertebral layer of deep cervical fascia (posteriorly), pretracheal layer of deep cervical fascia (anterior- medially) and superficial layer of deep cervical fascia (anterior-laterally).
IV. Lymphatics of the Neck: Levels and Sublevels
Level I Submental (Ia) and Submandibular (Ib) Triangles.
Level II Upper Jugular Chain (Upper third). Region bound by the digastric muscle superiorly and the hyoid bone (clinical landmark) or the carotid bifurcation (surgical landmark) inferiorly. Contains jugulodigastric node which is by far the most commonly involved node for
34 head and neck cancer. IIa contains nodes in the region anterior to the spinal accessory nerve and IIb posterior to the nerve.
Level III Mid-jugular Chain (Middle third). Region extends from the carotid bifurcation superiorly to the cricothyroid notch (clinical landmark) or omohyoid muscle (surgical landmark) inferiorly.
Level IV Lower Jugular Chain (Lower third). From cricoid/omohyoid to the clavicle inferiorly.
Level V Posterior Triangle. Posterior triangle group of lymph nodes are located along the lower half of the spinal accessory nerve and the transverse cervical artery. The supraclavicular nodes are also included in this group. The posterior boundary is the anterior border of the trapezius muscle, the anterior boundary is the posterior border of the sternocleidomastoid muscle, and the inferior boundary is the clavicle. Posterior neck- retroauricular and suboccipital (both superficial as well as deep to trap) regions are important for skin cancer.
Level VI Anterior (or Central) Compartment. Anterior compartment group comprises lymph nodes surrounding the midline visceral structures of the neck extending from the level of the hyoid bone superiorly to the suprasternal notch inferiorly. On each side, the lateral boundary is the medial border of the carotid sheath. Located within this compartment are the perithyroidal lymph nodes, paratracheal lymph nodes, lymph nodes along the recurrent laryngeal nerves, and precricoid lymph nodes. Hyoid to sternum, carotid to carotid.
Level VII Superior Mediastinum
35 Temporal and Infratemporal Regions
I. Connective Tissue Components of the Temporal and Infratemporal Regions
A. Osteology: 1. Temporal Fossa – Is located above the zygomatic arch. a. Frontal bone. b. Parietal bone. c. Temporal bone. d. Greater wing of the sphenoid bone. e. Zygomatic bone. 2. Infratemporal Fossa – Is located below the zygomatic arch. a. Maxillary bone. b. Sphenoid bone. c. Temporal bone (including tegmen tympani and tympanic plate). d. Palatine bone (pyramidal process). e. Zygomatic bone. 3. Mandible a. Head (condyle). b. Neck. c. Coronoid Process. d. Ramus. e. Angle. f. Mental Foramen. g. Lingula. h. Mylohyoid Groove. i. Mylohyoid Line. j. Mental Spine (Genial Tubercle).
B. Foramen of, or associated with the Infratemporal region: a. Foramen Ovale - For V3, lesser petrosal nerve (parasympathetic innervation is from CN IX) and accessory meningeal artery. b. Foramen Spinosum - For middle meningeal artery. c. Mandibular Foramen - For inferior alveolar nerve, artery and vein which courses in mandible to mental foramen. d. Petrotympanic Fissure - For anterior tympanic (Gasarian) artery and chorda tympani nerve. e. Pterygomaxillary Fissure - For infraorbital part of maxillary artery and posterior superior alveolar nerve branching from V2. f. External Acoustic Meatus - For the deep auricular artery. g. Posterior Superior Alveolar Foramina – For posterior superior alveolar nerve, artery and vein.
C. Fascia of Infratemporal Fossa-Masticator Space: a. Space formed by splitting of superficial layer of deep cervical fascia. b. External layer covers external surface of masseter muscle and continues up over zygomatic arch to cover external surface of temporalis muscle. c. Internal layer covers internal surface of medial pterygoid muscle.
36 d. Collectively, internal and external layers form masticator space which contains all structures dissected in the infratemporal fossa.
D. Ligaments of infratemporal fossa: 1. Stylomandibular ligament- Thickened superficial fascia of neck attached superiorly to styloid process and inferiorly to angle of mandible. 2. Sphenomandibular ligament- Runs inferiorly –anteriorly from sphenoid spine to lingula (near mandibular foramen on ramus). 3. Together these two ligament allow the mouth to open as it is protracted by the lateral pterygoids.
E. Temporomandibular Joint (TMJ):
1. Unusual because the articular surfaces are fibrocartilage instead of hyaline cartilage. 2. Continually undergoes remodeling as teeth are lost. 3 Articular capsule is a fibrous membrane that surrounds the joint. a. Attached to edges of the mandibular (glenoid) fossa. b. Attached to articular tubercle. c. Attached to neck of mandible. d. Thin above articular disk (meniscus). e. Thick inferiorly, therefore, disk moves with mandible. f. Capsule is reinforced laterally by temporomandibular ligament (or external lateral ligament). This extends from the zygomatic arch to neck of mandible. 4. Articular disk – located between the mandibular fossa of temporal bone and condyle of mandible. a. Takes on the size and shape of the joint. b. Composed primarily of dense fibrous connective tissue. c. Consists of thickened posterior band, thin intermediate zone and moderate sized anterior band. d. Disk anchored anteriorly and posteriorly to the temporal bone and mandible through anterior and posterior attachments. However, attachments allow disk to move about within capsule. 5. Blood and nerve supply enter joint posteriorly. Chief blood supply is from the superficial temporal and maxillary arteries and chief nerve supply is from the auriculotemporal nerve (branch of V3).
II. Myology of the Temporal and Infratemporal Region – 4 muscles
- Masseter - Temporalis - Lateral (external) pterygoid - Medial (internal) pterygoid
Note: All muscles of infratemporal fossa (listed above) are innervated by motor branches of V3. All receive blood supply from muscular branches of the maxillary artery.
A. Masseter Muscle: 1. Superficial portion: a. Origin arises inferior part of anterior 2/3 of zygomatic arch. b. Inserts on ramus and angle of mandible.
37 2. Deep portion: a. Origin arises from deep and inner surface of posterior 1/3 of zygomatic arch. b. Inserts on ramus and coronoid process of mandible. 3. Nerve supply a. Motor branches of CN V (specifically V3) enter deep (medial) surface by passing through the mandibular notch with masseteric artery and vein.
B. Temporalis Muscle: 1. Origin: From temporal fascia and temporal fossa on lateral side of skull. 2. Insertion: On lateral coronoid process and anterior border of ramus of mandible. 3. Nerves: Motor branch of CN V (V3), 2-3 branches that course superior to the two heads of the lateral pterygoid to insert on medial surface. 4. Arteries: Usually course with the nerves.
C. Lateral Pterygoid: 1. Origin: Upper part: Inferior lateral part of greater wing of sphenoid bone. Lower part: Lateral surface of lateral pterygoid plate. 2. Insertion: Both parts into neck of mandible and articular disk of TMJ. 3. Nerves: Motor branch of CN V (V3) just as it leaves the foramen. 4. Artery: Second part of maxillary artery.
D. Medial Pterygoid: 1. Origin: Medial surface of lateral pterygoid plate and posterior part of maxillary tuberosity. 2. Insertion: Lower medial ramus of mandible to the posterior-inferior border of the angle. 3 Nerves: Motor branch of CN V (V3) via a short branch medial to lingual and inferior alveolar branches. Anatomically close to the otic ganglion. Lingual nerve is joined by the chorda tympani nerve at the upper border of the medial pterygoid muscle E. General actions of masticator muscles: 1. Masseter, temporalis and medial pterygoid all act to close the jaw forcefully. 2. Lateral pterygoid protracts mandible (assisted by masseter and medial pterygoid) 3. Medial pterygoid and masseter deviate jaw to opposite side. 4. Temporalis deviates jaw to same side and retracts.
III. Neurology of Temporal and Infratemporal Region A. Mandibular Nerve (V3) Emerges from foramen ovale, medial (deep) to lateral pterygoid muscle and lateral to tensor veli palatine muscle (innervated by V3). It contains motor and sensory fibers. The motor division lies anteriorly (arching toward muscles) and the sensory division lies posteriorly.
SENSORY BRANCHES of the infratemporal fossa:
a. Buccal Nerve - Courses between the two heads of lateral pterygoid muscle and passes to the lateral surface of buccinator muscle. It does not innervate the buccinator muscle (innervated by buccal nerve of facial nerve) but it does provide sensory innervation (pain temperature and touch) to lateral cheek (over buccinator region).
38 b. Auriculotemporal Nerve - Arises from 2 stems which surround the middle meningeal artery then unite posteriorly. It continues to course posteriorly then superiorly to run between TMJ and external acoustic meatus (EAC). It supplies sensation to the auricle, TMJ as well as skin over the zygomatic arch, parotid, and temporal regions.
c. Inferior Alveolar Nerve - Enters the mandibular foramen on medial surface of the ramus 1.5-2cm below the mandibular notch. Prior to entering the mandibular foramen it gives off the mylohyoid nerve (which innervates the mylohyoid muscle and the anterior belly of digastric muscle). Soon after entering the foramen the inferior alveolar nerve gives off branches that form the inferior dental plexus which in turn give off small gingival and dental nerves to innervate the teeth. The incisors innervated by a separate plexus that forms before the nerve exits the mental foramen.
d. Mental Nerve - Large terminal branch of the inferior alveolar nerve that exits mandible via the mental foramen to supply the skin of the chin, lower lip, mucosa of lip and adjacent gingiva.
e. Lingual Nerve - Emerges from V3 and receives the chorda tympani nerve (at the superior border of medial pterygoid). The lingual nerve descends on lateral surface of medial pterygoid muscle and anterior to the inferior alveolar nerve. It curves anteriorly at the level of mylohyoid and laterally to tongue. At this location preganglionic parasympathetic fibers (originally from facial-chorda tympani nerve) leave the lingual nerve to synapse in the submandibular ganglion. The lingual nerve continues anteriorly to base of tongue. It distributes sensory fibers (pain, temperature and touch) to the anterior 2/3’s of the tongue. As will be noted below, taste fibers are also distributed in this same region of the tongue. These fibers originated from the facial nerve (specifically via the chorda tympani nerve).
MOTOR BRANCHES of the infratemporal fossa
f. Nerve to the Mylohyoid – Emerges from the inferior alveolar nerve, courses in the mylohyoid groove and innervates the mylohyoid muscle and anterior belly of the digastric muscle.
g. Nerves to the Muscles of Mastication – Emerge from the mandibular nerve once it passes through the foramen ovalae and innervates the masseter, temporalis, medial pterygoid and lateral pterygoid muscles.
B. Maxillary Nerve (V2) Gives rise to one nerve that enters the infratemporal fossa by traversing the pterygomaxillary fissure:
a. Posterior Superior Alveolar Nerve - Enters maxillary bone through posterior superior alveolar foramen located on the maxillary tuberosity. Provides sensory (pain, temperature and touch) fibers to the upper (maxillary) posterior teeth and gingiva.
C. Otic Ganglion (Innervates parotid gland, origin of fiber system is associated with CN IX)
1. Anatomically lies on medial side of V3 just below the level of the foramen ovale.
39 2. Is functionally parasympathetic therefore a synapse occurs within this ganglion between parasympathetic preganglionic fiber terminals and parasympathetic postganglionic cell bodies. a. Preganglionic parasympathetic fibers are not from mandibular nerve but from CN IX via the lesser petrosal nerve which passed through the foramen ovale. b. Postganglionic parasympathetic fibers arise from the otic ganglion and travel to the parotid by joining the auriculotemporal nerve of V3. 3. Postganglionic sympathetic fibers from the middle meningeal artery pass through the otic ganglion and join the auriculotemporal nerve as do the postganglionic parasympathetic fibers.
D. Chorda Tympani - Branch of the Facial Nerve.
1. Major branch of the facial nerve that arises from the facial nerve in the middle ear (tympanic cavity). 2. The chorda tympani leaves the middle ear through the petrotympanic fissure (found medial to the spine of the sphenoid, actually makes a groove in the medial surface of the spine), enters the infratemporal fossa and then joins the lingual nerve. 3. Functional contribution of the chorda tympani nerve: a. Special sensory fibers (taste) whose cell bodies reside in the geniculate ganglion. The terminal fibers from the chorda tympani are distributed to the anterior 2-/3’s of the tongue. Therefore, facial nerve (CN VII) provides taste to the anterior 2/3’s of the tongue (via chorda) and the trigeminal (CN V) provides pain, temperature and touch fibers to the anterior 2/3’s of the tongue (via lingual nerve) for taste. b. The chorda tympani also contains autonomic preganglionic parasympathetic fibers which are destined to terminate on postganglionic cell bodies located in the submandibular ganglion.
IV. Angiology of the Temporal and Infratemporal Region A. Arterial supply-Maxillary Artery 1. Maxillary artery arises as 1 of 2 of the terminal branches of external carotid (other terminal branch is the superficial temporal artery). 2. It branches horizontally from the external carotid at upper 1/3 of ramus of mandible. 3. It may course lateral or medial to inferior division of the lateral pterygoid muscle. B. Maxillary artery is divided into 3 major parts or segments: 1. First Part (Mandibular portion) - 5 branches that all pass through foramen: a. Deep Auricular Artery – Supplies the external acoustic meatus. b. Anterior Tympanic Artery- Supplies the middle ear (tympanic cavity by coursing with the chorda tympani nerve through the petrotympanic fissure). c. Middle Meningeal Artery – To meninges (specifically the dura matter) and calvaria (roof of skull). 1) Most important arterial supply to dura mater – supplies 4/5ths. 2) Enters skull through foramen spinosum. Note: anterior meningeal artery is a branch of the anterior ethmoid artery and posterior meningeal artery is formed by branches from the vertebral artery and ascending pharyngeal artery. d. Accessory Meningeal Artery- When present, runs through foramen ovale to supply dura.
40 e. Inferior Alveolar Artery – Enters mandible via manduibular foramen with nerve to supply the mandible, inferior dental arcade, and chin. 2. Second part (Pterygoid portion) – Muscular branches: a. Masseteric branches. b. Deep temporal branches. c. Buccal branches. d. Branches to both pterygoids (medial and lateral). 3. Third Part (Pterygopalatine portion) – to maxillary bone: a. Passes deep to 2 heads of the lateral pterygoid into the pterygopalatine fossa. b. Give rise to the: i. Posterior superior alveolar artery. ii. Infraorbital artery. iii. Descending palatine artery – supplies palate. iv. Artery of pterygoid canal (Vidian artery) – supplies pharynx and auditory tube. v. Sphenopalatine artery- Supplies nasal cavity and is the most common source of hemorrhage from maxillary artery. vi. Pharyngeal branch - supplies pharynx and auditory tube.
Note: We will cover vessels ii-v in the next section of the head and neck unit.
C. Venous Drainage 1. Pterygoid Plexus: a. Large venous plexus that surrounds maxillary artery in the infratemporal fossa and lies on both sides of lateral pterygoid muscle. Chief drainage is via the maxillary vein. b. The maxillary vein joins the superficial temporal vein to form the retromandibular vein. 2. Also connected to: a. Facial vein via deep facial vein, which runs with the buccal artery and nerve. b. Cavernous sinus by a plexus through the foramen ovale and rotundum. c. Inferior ophthalmic vein through the inferior orbital fissure.
I. Divided into three major sections: A. Nasopharynx. B. Oropharynx. C. Laryngopharynx (Hypopharynx).
General function of pharynx is to conduct food to the esophagus and air to the larynx (and eventually the lungs).
II. Entire pharyngeal wall is composed of 4 major layers. From lumen (anteriorly) towards the posterior neck they include: A. Mucous membrane layer (mucosa). 1. In nasopharynx and oropharynx it contains tonsils. 2. It is tightly adherent to the next (deeper) layer called the pharyngobasilar fascia. B. Pharyngobasilar fascial layer - This is a connective tissue layer or sheet. 1. It lies between the mucosal and muscular layers. Note, where there is no muscle superiorly at base of skull, the pharyngobasilar fascia is adjacent to the buccopharyngeal fascia (for buccopharyngeal fascia see D. below). 2. Originates at the pharyngeal tubercle (on the base of the occipital bone) and laterally from this point on the base of the skull. 3. It forms the fibrous tonsillar bed. 4. Inferiorly it is thin and attaches to the pterygomandibular raphe (or ligament), hyoid bone and thyroid cartilage. C. Muscular layer (three external muscles): Originates from the pharyngeal tubercle of the occipital bone. 1. Superior constrictor. 2. Middle constrictor. 3. Inferior constrictor. D. Buccopharyngeal fascial layer - Upward extension of visceral (pretracheal) fascial layer. 1. It is the most external layer (will readily see and appreciate during dissection). Therefore, it covers the external surface of pharyngeal constrictor muscles. 2. Contains pharyngeal plexus (nerves of CN IX, CN X, and sympathetic chain including extensive plexus of veins).
III. Nasopharynx- Located posterior to nasal cavity, above soft palate. A. Boundaries: 1. Anterior: Posterior opening of the nasal cavity (choanae). 2. Inferior: Inferior surface of soft palate (note uvula). 3. Roof: Skull. 4. Posterior: Spinal column. B. Lateral wall has opening of the Eustachian tube (E.T.). Also known as auditory tube or pharyngotympanic tube. 1. The cartilage of the tube has an inverted J shape. 2. The cartilage forms the torus tubarius (torus = swelling, rounded elevation). 3. Fossa behind the torus tubarius is the pharyngeal recess (fossa of Rosenmüller). C. Posterior wall is covered with lymphoid tissue that forms the pharyngeal tonsil (also known as adenoids or adenoid pad). 1. Enlargement may result in nasal obstruction.
42 2. May also occlude the eustachian tube orifice. D. Pharyngeal Bursa 1. Midline sac-like depression just at the superior margin of superior constrictor.
IV. Oropharynx – General region - located posterior to the tongue/oral cavity. A. Borders: 1. Roof- Soft palate (note uvula). 2. Anterior – Posterior part of oral cavity. 3. Lateral – Palatine arches and palatine tonsil. 4. Inferior – Superior tip of epiglottis. B. Area between epiglottis and the tongue is the vallecula. It is formed by three folds: 1. Two lateral glossoepiglottic folds. 2. Median glossoepiglottic fold. C. Lingual tonsils – Occur in base of tongue, anterior to vallecula. D. Palatine tonsils – On lateral wall of oropharynx. 1. The palatine tonsils are enclosed by tonsillar pillars (or tonsillar arches): a. Anterior pillar – Formed by the palatoglossus muscle. b. Posterior pillar – Formed by the palatopharyngeus muscle. 2. Relations to adjacent structures: a. Located between the tonsillar pillars. b. Folds of mucosa around the tonsil may be present. i. Anterior fold is known as the triangular fold. ii. Superior fold is known as the semilunar fold. c. Superior constrictor is superior. d. Lateral to palatine tonsil is glossopharyngeal nerve, stylopharyngeus and styloglossus muscles, stylohyoid ligament, ascending pharyngeal artery and ascending palatine branch of facial artery. e. Styloid process: i. Normally does not reach the tonsillar fossa. f. Vascular supply of palatine tonsils: i. Dorsal lingual artery (branch from lingual artery). ii. Ascending palatine artery (branch from facial artery). iii. Tonsillar artery (branch from facial artery). iv. Ascending pharyngeal artery. v. Lesser palatine artery (branch of from descending palatine artery that arises from the maxillary artery in the pterygopalatine fossa). Note: italicized arteries above are all direct branches of the external carotid artery. g. Venous drainage of palatine tonsils is via plexus that connects primarily by the tonsillar branch of the lingual vein. h. Nerve supply of palatine tonsils: i. Primarily from the tonsillar branch of glossopharyngeal nerve. ii Some small branches from the lesser palatine nerves (derived from V2 of the pterygopalatine fossa) supply sensation. iii. The main trunk of the glossopharyngeal nerve (CN IX) may be exposed at the inferior lateral pole of palatine tonsil and may be damaged during tonsillectomy. i. Lymphatics: i. Majority pass into deep cervical chain.
V. Laryngopharynx (Hypopharynx) – Located posterior to larynx. A. Extends from superior tip of epiglottis (level of hyoid bone) to lower border of cricoid cartilage. B. Larynx located anterior.
43 C. Contains piriform recess.
VI. Waldeyer’s tonsillar ring (pronounced Vol-di-erz): Ring of lymphatic tissue that encircles the nasopharynx and oropharynx. Consists of 2 palatine tonsils, lingual and pharyngeal tonsils. Waldeyer’s ring is specifically formed by: 1. Anterior inferior: Lingual tonsil. 2. Lateral: Palatine tonsils. 3. Posterior superior: Pharyngeal tonsil (adenoids).
VII. Musculature of the Pharynx – Categorized as External and Internal groups. A. General comments: 1. Superior, middle and inferior constrictors insert into corresponding muscle posteriorly, at the pharyngeal raphe. The pharyngeal raphe is attached to the pharyngeal tubercle of the basilar part of the occipital bone. All constrictors constrict wall of pharynx. 2. The palatopharyngeus, salpingopharyngeus and stylopharyngeus fan out to insert on the inner surface of pharynx. All elevate pharynx. 3. All pharyngeal muscles (external and internal), except for the stylopharyngeus muscle (which is innervated by CN IX), are innervated by CN X via the pharyngeal plexus.
B External Muscles of Pharynx: 1. Superior constrictor: a. Arises from hamulus of medial pterygoid process, pterygomandibular raphe, mandible located posterior to mylohyoid line. b. Inserts into pharyngeal raphe posteriorly. 2. Middle constrictor: a. Arises from greater and lesser cornu of the hyoid bone and the lower part of stylohyoid ligament. b. Inserts into pharyngeal raphe posteriorly. c. Overlaps with superior and inferior constrictors 3. Inferior constrictor: a. Arises from the oblique line of the thyroid cartilage and the posterior part of the cricoid cartilage. b. Inserts into pharyngeal raphe posteriorly. c. Lower part forms the cricopharyngeal sphincter (is actively closed except when swallowing).
C. Internal Muscles of Pharynx: 1. Palatopharyngeus (forms the posterior tonsillar pillar): a. Arises from hard and soft palate. b. Inserts into wall of pharynx and thyroid cartilage. 2. Salpingopharyngeus (absent in 30% of cases). a. Arises from end of the eustachian tube. b. Inserts into wall of pharynx (fibers interdigitate with palatopharyngeus). 3. Stylopharyngeus: a. Arises from medial side of styloid process. b. Inserts into wall of pharynx medial to middle constrictor. c. Assists in defining the boundary between the superior and middle constrictors.
44 d. Only pharyngeal muscle NOT innervated by CNX. It receives its motor innervation from CN IX (Glossopharyngeal nerve).
VIII. Arterial Supply to Pharynx: A. Primarily from the ascending pharyngeal and superior thyroid arteries.
IX. Pharyngeal Venous Plexus: A. Extensive plexus of veins surrounding pharynx (externally) that communicates with: 1. Pterygoid plexus, superior thyroid veins, lingual veins, facial veins and directly with internal jugular veins.
X. Lymphatics of Pharynx: A. Rich, especially around the tonsil. B. Drainage path is: 1. Roof and posterior wall: Through pharyngeal wall and to lateral pharyngeal node (located just medial to internal carotid at base of skull) and retropharyngeal nodes (located posterior to constrictors). 2. Tonsillar (lateral) region: Drain lateral directly into deep cervical chain. 3. Inferiorly into larynx.
XI. Nerve Supply to Pharynx: Pharyngeal Plexus. A. Plexus formed by contributions from CN IX, CN X and postganglionic sympathetic branches from the superior cervical ganglion. 1. CN IX (Glossopharyngeal Nerve): a. Provides major sensory supply to pharynx. b. Provides motor innervation to the stylopharyngeus muscle. 2. CN X (Vagus Nerve): a. Provides major motor innervation to pharynx. Innervates all external and internal pharyngeal muscles except the stylopharyngeus (CN IX). The inferior constrictor also receives motor branches from the external branch (external laryngeal nerve) of the superior laryngeal nerve. The superior laryngeal nerve is also a branch of the vagus. 3. Sympathetic Chain – Superior Cervical Ganglion: a. Postganglionic sympathetic fibers from the superior cervical ganglion join the pharyngeal plexus to innervate vasculature.
XII. Pharyngeal Spaces A. Lateral pharyngeal space (continuous with retropharyngeal space). B. Retropharyngeal space (continuous with retroesophageal/visceral space.
45 Nasal Cavity
A. Respiration – Air is warmed, humidified and filtered. B. Olfaction – Detects special sensation of smell. C. Phonation – Amplifies and alters sound initially produced by larynx.
II. Structural support – Formed of bone and cartilage. A. External Nose 1. Nasal bones- narrower and thicker above, wider and thinner below. Articulate firmly with frontal bone 2. Nasal Cartilages- usually described as being formed by several major cartilages (lateral, greater alar) and a variable number of smaller (accessory or lesser) ones. B. Lateral Nasal Wall: (bones-maxillary, ethmoid, sphenoid, lacrimal) 1. Bounds the paranasal sinuses and drains them. 2. 3-4 turbinates (conchae) present to channel airflow. 3. Beneath turbinates are spaces that are named according to the turbinate they are associated with (superior meatus, middle meatus and inferior meatus). 4. Inferior turbinate and meatus: a. Independent bone that is covered with thick mucous membrane. b. Typically, only lacrimal duct empties in inferior meatus (the anterior part) via nasolacrimal ostium. 5. Middle turbinate and meatus: a. Formed by part of ethmoid bone. b. At anterior end is frontal recess opening for frontonasal duct. The duct drains the frontal sinus and anterior ethmoid cells. c. Landmarks in middle meatus: 1) Uncinate process – curved laminar process of ethmoid bone. 2) Ethmoid bulla - rounded projection of lateral wall with ethmoid air cells just laterally. 3) Ethmoid infundibulum – curved channel that drains frontal sinus, ethmoidal cells, and maxillary sinus (via maxillary hiatus or ostium). 4) Semilunar hiatus. 6. Superior turbinate and meatus: a. Formed by part of ethmoid bone b. Shorter, thinner, less vascular than other turbinates. c. Includes olfactory epithelium. d. Posterior ethmoid air cells open into shallow meatus. 7. Supreme turbinate: a. Formed by part of ethmoid bone. b. Rarely represents more than a fold of mucosa. c. Sphenoethmodial recess is a small space posterior and superior.
C. Nasal septum (midline) - Formed by: 1. Perpendicular plate of ethmoid bone. a. Forms upper 1/3 of septum and is continuous with cribriform plate. b. Articulates with: 1) Anterior with nasal and frontal bones.
46 2) Posterior with sphenoid bone. 3) Posterior inferior with vomer. 4) Anterior inferior with septal cartilage. 2. Vomer (Plow bone): a. Articulates with ethmoid bone (perpendicular plate), sphenoid bone, maxillary (crest) bone, palatine bone and septal cartilage. 3. Septal cartilage (quadrangular cartilage): a. Articulates with vomer, ethmoid bone (perpendicular plate) and maxillary bone (crest and anterior nasal spine).
III. Neural Innervation of Nasal Cavity A. Sensory Innervation: Ophthalmic division of CN V (V1). 1. Distributes the nasociliary nerve which branches into posterior and anterior ethmoidal nerves. a. Posterior ethmoidal nerve supplies posterior ethmoidal and sphenoid sinuses and mucosa over superior/supreme turbinate. b. Anterior ethmoidal nerve supplies anterior ethmoidal sinus and anterior nasal cavity. 1) Leaves orbit via anterior ethmoid foramen. 2) Enters cranial cavity below dura. 3) Courses anterior along cribriform plate. 4) Leaves cranial cavity through ethmoidal slit near crista galli to enter the anterior region of the nasal cavity. 5) Supplies anterior and superior part of lateral and medial walls. 6) Small branch leaves the nasal cavity to course between the nasal bone and upper lateral cartilages to innervate the skin at the tip of the nose (external nasal nerve).
B. Sensory Innervation: Maxillary division of CN V (V2). 1. Maxillary division supplies vestibule of nose (anterior part of nostrils) and nasal cavity proper. 2. The maxillary division (maxillary nerve) courses through the foramen rotundum to the pterygopalatine fossa. 3. The maxillary nerve then provides all the nerves which leave the pterygopalatine fossa with sensory fibers. a. Sensory nerves, which are from maxillary division, do not synapse within the pterygopalatine ganglion (only parasympathetic component via nerve in the pterygoid canal synapse in the pterygopalatine ganglion) but pass through the ganglion. b. Most nasal branches arising from the pterygopalatine fossa exit the pterygopalatine fossa through the sphenopalatine (or pterygopalatine ) foramen. 1. The foramen can be found just posterior and superior to the middle turbinate. 2. Nerves coursing through the sphenopalatine foramen are classified as: i. Posterior superior lateral nasal branches which supply superior and middle turbinates and posterior part of the ethmoid bone.
47 ii. Posterior superior medial nasal branches which supply the septum, posteriorly and superiorly iii. Nasopalatine nerve which supplies septum and enters incisive foramen to innervate anterior hard palate. c. Posterior inferior lateral nasal branches arise from the descending nerves in the palatine canal (from greater palatine nerve). C. Autonomic Innervation: Primary autonomic innervation (sympathetic and parasympathetic) is through nerve fibers branching from the pterygopalatine ganglion. However, only parasympathetic nerve terminals (preganglionic) will synapse on cell bodies (postganglionic parasympathetic cell bodies) found within the pterygopalatine ganglion. Sympathetic fibers (axons) pass through ganglion without synapsing. 1. Parasympathetic Innervation Pathway: a. Preganglionic parasympathetic fibers arise from the facial nerve. b. The greater petrosal nerve (GPN) emerges from the facial nerve (at the level of the geniculate ganglion) and passes through the hiatus of the GPN to enter the middle cranial fossa. Therefore the GPN is composed of preganglionic parasympathetic fibers. c. The GPN courses along the petrous part of the temporal bone then leaves the middle cranial fossa by entering the foramen lacerum. d. Within the foramen lacerum the GPN is joined by the deep petrosal nerve (sympathetic fibers from the carotid plexus) to form the nerve in the pterygoid canal (also called the Vidian nerve). Therefore, the nerve in the pterygoid canal contains both parasympathetic (preganglionic) and sympathetic (postganglionic) components. e. The nerve in the pterygoid canal (Vidian nerve) passes completely through the pterygoid canal of the sphenoid bone. f. Immediately after coursing through the pterygoid canal, the nerve enters the pterygopalatine fossa. g. Parasympathetic fibers (preganglionic) end to synapse in the pterygopalatine ganglion and sympathetic fibers (postganglionic) pass through the ganglion. 2. Sympathetic Innervation Pathway: a. Preganglionic sympathetic fibers originate form preganglionic sympathetic cell bodies located at upper thoracic levels of the spinal cord (i.e., T1). b. Preganglionic sympathetic fibers ascend in the sympathetic chain to reach the superior cervical ganglion. Once in the ganglion the fibers end and synapse on postganglionic sympathetic cell bodies located in the ganglion. c. Postganglionic cell fibers arise from the ganglion, course along the internal carotid artery to form the internal carotid plexus (plexus is entirely postganglionic sympathetic nerve fibers). d. In the carotid canal, the deep petrosal nerve arises from the internal carotid plexus on the internal carotid artery. Therefore, the deep petrosal nerve is sympathetic. e. The deep petrosal nerve (sympathetic division) is joined by greater petrosal nerve of CNVII (parasympathetic branch of facial nerve) in the bottom of the foramen lacerum. Once joined the nerve is referred to as the nerve of the pterygoid canal (or Vidian nerve). f. After coursing through the pterygoid canal, the nerve of the pterygoid canal enters the pterygopalatine fossa.
48 g. Sympathetic fibers do not synapse within the pterygopalatine ganglion but pass through it (only parasympathetic fibers end to synapse on parasympathetic cell bodies in the ganglion). 3. In the pterygopalatine fossa, parasympathetic nerve fibers and sympathetic nerve fibers distal to the pterygopalatine ganglion then travel within the sheathes of sensory branches of V2 to supply the nose (see branches of V2 to the nose in section “B) above, “Sensory Innervation” above).
D. Special Sensory Innervation: (CN I, Olfactory nerve) a. Olfactory epithelial cells (receptor cells) located in roof, or superior region of the nasal cavity (embedded in mucosal lining). These specialized cells detect smell (the surface receptors sense specific, unique molecules) and conduct this odorant-related information through fibers passing through cribriform foramina and to the olfactory bulb in the cranial cavity.
IV. Arteries of Nasal Cavity (general vascular supply is from both external and internal carotid arterial systems) A. Internal Carotid Supply. Anterior and posterior ethmoidal arteries. 1. Arise from ophthalmic artery in the orbit. 2. Pass through respective canals into anterior cranial fossa. 3. Course anterior and medial to cribriform plate to enter nose. 4. Posterior Ethmoid Artery: a. Small in size. b. Supplies area located medial and lateral to superior/supreme turbinate. 5. Anterior Ethmoid Artery: a. Larger and supplies anterior 1/3 of lateral wall and septum. b. Anastomoses with sphenopalatine artery branches posteriorly. c. Anteriorly, a small arterial branch (external nasal artery) may leave the nasal cavity by coursing between the nasal bone and upper lateral cartilages to supply the skin at the tip of the nose. The external nasal artery accompanies the external nasal nerve (branch of V1). B. External Carotid Supply: Arises from the maxillary artery of the infratemporal fossa. The maxillary artery enters the pterygopalatine fossa by first traversing the pterygomaxillary fissure. 1. Sphenopalatine Artery - A branch of the maxillary artery which leaves the pterygopalatine fossa through the sphenopalatine foramen to enter the nasal cavity. In general, the artery supplies the posterior part of the nasal cavity. 2. Septal Artery – Medial continuation of the sphenopalatine artery that courses on the septum (vomer) toward the anterior midline region of the nasal cavity. Terminal branches enter the incisive foramen/canals.
V. Venous Drainage A. Sphenopalatine veins drain into pterygoid plexus (in infratemporal fossa) which empties into the maxillary vein (then into the internal jugular vein). B. Anterior and posterior ethmoidal veins drain into the superior ophthalmic vein (then cavernous sinus).
VI. Frontal Sinus A. Several sinuses may exist in frontal bone and are rarely symmetrical with a deviated septum to one side or the other side of the midline.
49 B. Normally extends superiorly into bone and posteriorly over orbit. C. Drained by frontonasal duct to infundibulum in middle meatus. D. Supraorbital nerve and vessels supply the frontal sinuses.
VII. Ethmoid Sinus: Drained by many ostia (openings) located on lateral nasal wall. A. Anterior ethmoid cells. Drain through ostia under middle turbinate (into middle meatus). B. Middle ethmoidal cells. Drain through ostia under middle turbinate (into middle meatus). C. Posterior ethmoid cells. Drain through ostia under superior turbinate (into superior meatus). D. Arterial and nerve supply to ethmoids: 1. Anterior and middle cells are supplied by the anterior ethmoidal nerves and vessels. 2. Posterior cells are supplied by the posterior ethmoidal nerves and vessels.
VIII. Sphenoid Sinus A. Drain through ostia (small openings) at the sphenoethmodial recess (above the superior turbinate) (note: ostium – is a small opening, singular). B. Usually separated by a bony septum. C. Relationships of sphenoid: 1. Superior: Middle cranial fossa and pituitary gland 2. Lateral: Cavernous sinus and interior carotid artery. 3. Posterior: Posterior cranial fossa and brainstem. 4. Inferior: Roof of nasopharynx. D. Blood supply and innervation is the same as the posterior ethmoidal cells (posterior ethmoidal artery, vein, and nerve).
IX Maxillary Sinus: A. Largest of sinuses. B. Drains into middle meatus (via ostia located high on medial wall and open into infundibulum and semilunar hiatus then middle meatus). C. Relationships: 1. Anterior: Facial surface 2. Superior: Orbit 3. Media: Nasal Cavity 4. Inferior: Alveolar and palatine process. 5. Posterior: Infratemporal fossa D. Blood supply and innervation through posterior superior alveolar, middle superior alveolar and anterior superior alveolar nerves and vessels.
50 Oral Cavity I. Palate:
A. Hard (Bony) Palate 1. Formed by palatine processes of the two maxillae that are continuous anterior and lateral with alveolar process of maxilla. 2. Marked anterior by the incisive fossa. 3. Two sutures: a. Longitudinal Suture - Between two adjacent maxillary bones. b. Transverse Suture - Between maxillary and palatine bones. 4. Palatine bone forms the greater and lesser palatine foramen. 5. Posterior midline of the two palatine bones forms the posterior nasal spine. 6. Hard palate forms ¾ of total length of the palate.
B. Soft (Fibromuscular) Palate 1. Fibromuscular shelf of tissue that projects posterior/inferior from the hard palate. 2. Continuous with lateral pharyngeal walls. 3. The cord of the soft palate is the palatine aponeurosis which is firmly attached to hard palate, hamulus and tendon of tensor veli palatini and the levator veli palatini. 4. Musculus uvulae- midline muscle that extends posteriorly and inferiorly from nasal spine of palatine bone. 5. Palatopharyngeus muscle - forms the posterior tonsillar pillar (or arch). Pulls the pharynx forward preventing food from entering the nasopharynx while simultaneously forming an inclined plane directing the bolus of food posteriorly and inferiorly. 6. Palatoglossus muscle - forms the anterior tonsillar pillar (or arch). In general, the muscular fibers are arranged in a sphincter-like arrangement. Elevates tongue, closes oropharyngeal isthmus and participates in the initiation of swallowing. 7. Levator veli palatine: a. Contributes the main bulk of muscle to the soft palate. b. Arises from the petrous apex of the temporal bone in front of the carotid canal and a few fibers from the lower middle part of Eustachian tube. c. It inserts into the palatine aponeurosis. 8. Tensor veli palatine: a. Muscle is of significance for opening of the Eustachian tube. b. Lies anterior and lateral to levator veli palatini. c. Arises from sphenoid spine, scaphoid fossa (base of medial pterygoid plate) and from the cartilaginous wall of Eustachian tube. d. From this broad base it tapers down to a tendon which courses around the hamulus of the medial pterygoid plate. e. Tendon turns at nearly right angles to insert into the tendon from the other side. f. Tendons of this muscle form the bulk of the palatine aponeurosis.
C. General Actions 1. Palatoglossus and palatopharyngeus assist in swallowing (see above). 2. Musculus uvulae draws soft palate up (elevates) and forward (shortens or retracts). 3. The levator veli palatini lifts and pulls the soft palate posterior to come in contact with the posterior pharyngeal wall preventing food from entering the nasopharynx.
51 4. The tensor veli palatini tenses the palate, slightly depresses it and opens the Eustachian tube. D. Nerves of Palate 1. Motor nerves of soft palate: a. All muscles (except the tensor veli palatini which is innervated by CN V3) are innervated by motor fibers from CN X via the pharyngeal plexus. 2. Sensory and Autonomic Nerves associated with Palate: a. Sensory and autonomics arise primarily from pterygopalatine fossa and descend from fossa within the palatine canal. b. Greater palatine nerve: 1. Exits the greater palatine foramen. 2. Courses anteriorly along hard palate. c. Lesser palatine nerve: 1. Runs parallel to the greater palatine nerve in palatine canal and exits the canal via the lesser palatine foramen. 2. Courses posteriorly to soft palate and upper pole of palatine tonsil. 3. Thought to consist primarily of sensory afferents but also special sense taste afferents to the soft palate (via CN VII – greater petrosal nerve).
E. Arterial Supply: 1. Descending palatine artery a. Arises from maxillary artery in the pterygopalatine fossa not far from the sphenopalatine artery (which enters the nasal cavity). b. Inferiorly in the palatine canal the descending palatine artery branches into: 1) Lesser palatine artery: a) Exits palatine canal through lesser palatine foramen. b) Supplies posterior alveolus, hard and soft palate. 2) Greater palatine artery: a) Exits palatine canal through greater palatine foramen. c) Supplies hard palate as it courses forward to incisive foramen. d) Terminal branch passes through incisive foramen/canals to supply anterior floor of nose. Overlaps with terminal branches of septal artery.
F. Venous and Lymphatic Drainage: 1. Venous drainage from the palate is into the pterygoid plexus (via pterygopalatine fossa) and into the pharyngeal plexus posteriorly (which in turn communicates with the pterygoid plexus). 2. Lymphatics from hard palate drain down and anteriorly to the deep cervical chain. 3. Lymphatic drainage from anterior soft palate is to deep cervical chain. 4. Posterior soft palate drains to the retropharyngeal space.
I. General Features A. Consists of three parts, the root, body and tip (apex). B. Covered by Mucosa (mucous membrane) and lingual follicles (tonsils) within mucosa. C. Concerned with mastication (chewing), taste, swallowing, speech and respiration (and possibly - emotional expression). D. Is situated in the oral cavity and partly in the oropharynx. E. Is loosely attached to the floor of the mouth by the lingual frenulum. F. Dorsum of tongue: 1. There are several types of papillae (taste buds): a. Papilla in anterior 2/3’s of tongue are innervated by CN VII. b. Papilla in posterior 1/3rd of tongue are innervated by CN IX. These are referred to as the vallate papilla and are arranged in a V-like configuration at the junction of the anterior 2/3 and posterior 1/3 of the tongue. c. Groove or sulcus behind the vallate papilla is known as the terminal sulcus. The foramen cecum (pit of the outgrowth of the thyroid gland) is located at tongue the midline, where the left and right extensions of the terminal sulcus join. The lingual tonsils are located posterior to the terminal sulcus.
II. Extrinsic Muscles of the Tongue A. Consist of four (paired) muscles. B. Two muscles (genioglossus and hyoglossus) arise inferiorly and extend upward into the tongue. Both represent the largest of the extrinsic tongue muscles. 1. Genioglossus muscle: a. Arises from internal portion of the anterior mandible, specifically from the mental spine (or genial tubercle). (genial = chin) b. Fibers course posteriorly from mandible, arch superiorly with some terminal fibers curving anteriorly . c. Lowest branches extending posteriorly insert into the hyoid bone. 2. Hyoglossus muscle: a. Arises from the body and the greater horn of the hyoid bone. b. Passes into the lateral part of the tongue to interlace with fibers of the styloglossus muscle. c. Lingual nerve and hypoglossal nerve lie lateral to the muscle. d. Lingual artery lies deep to hyoglossus but lateral to genioglossus. e. Submandibular duct, submandibular gland and sublingual gland are also located lateral to the hyoglossus muscle.
C. Two muscles (styloglossus and palatoglossus) arise superiorly, laterally and posteriorly: 1. Styloglossus muscle: a. Arises from lower end of styloid process and stylohyoid ligament. b. Passes medial to medial pterygoid muscle and lingual nerve inserting into the superior lateral region of the posterior tongue. 2. Palatoglossus muscle: a. Small muscle that forms the anterior tonsillar pillar (or arch). b. Arises from the palatine aponeurosis. c. Inserts into the superior lateral region of the posterior tongue.
III. Intrinsic Muscles of the Tongue A. Complicated bundles of heavily interlaced fibers commixed amongst connective tissue septa (strongest is in midline). Lingual septum (septum linguae) lies in the midline between nerves and vessels of the tongue. B. Superior and inferior longitudinal muscles are present. 1. Superior attach to the mucosa of tongue. 2. Inferior lies lower in tongue between genioglossus and hyoglossus and attach to hyoid bone. C. Transverse and vertical muscles are heavily interlaced. In general the bulk of these fibers are located between the superior and inferior longitudinal fibers.
IV. General Actions of the Tongue A. Intrinsic muscles produce fine and detailed changes in shape for chewing, swallowing, speaking and singing for example. B. Extrinsic muscles primarily pull the tongue forward (genioglossus), backward (styloglossus), upward (styloglossus and palatoglossus) and downward (genioglossus and hyoglossus).
V. Innervation of the Tongue Muscles A. Muscular: 1. Both groups (extrinsic and intrinsic) are innervated by the hypoglossal nerve (CN XII) except the palatoglossus muscle which is innervated by CN X. B. General Sensation (pain, temperature and touch) of Tongue: 1. Trigeminal fibers (CN V) of lingual nerve innervate the anterior 2/3 of tongue. 2. Glossopharyngeal nerve (CN IX) fibers are distributed to posterior 1/3 of tongue. C. Taste (Special Sense) 1. Anterior 2/3 of tongue: Pseudounipolar cell bodies in geniculate ganglion (of facial nerve) give rise to peripherally directed fibers that leave facial nerve and form the chorda tympani nerve. The chorda tympani then joins the lingual nerve and enter anterior 2/3 of tongue to provide taste sensation to this part of the tongue. 2. Posterior 1/3 of tongue: Pseudounipolar cell bodies in the inferior ganglion of glossopharyngeal nerve (CN IX) give rise to peripherally directed fibers that continue within the glossopharyngeal nerve to enter the posterior region of the tongue. At this location the taste fibers are distributed to specialized cells located on the dorsal surface of tongue.
VI. Blood Supply and Venous Drainage of the Tongue A. Lingual Artery – Gives rise to dorsal lingual artery posteriorly and divides into sublingual artery and deep lingual artery anteriorly. Located deep (medial) to the hyoglossus muscle as it courses from the external carotid artery. B. Lingual Vein – Same branches as lingual artery. That part which accompanies the hypoglossal nerve in the neck is referred to as the vena comitans of the hypoglossal nerve. This portion of the vein is located superficial (lateral) to the hyoglossus muscle.
54 VII. Teeth A. Divided into upper and lower jaws and their dental arcades. B. Gingivae (gums) - fibrous tissue covered by mucous membrane and is attached to bony alveolar processes and the neck of the teeth. C. Inferior (Mandibular) alveolar arch - is supplied by the inferior alveolar nerve (V3), artery and vein. D. Superior (Maxillary) alveolar arch - is supplied by the posterior superior alveolar, middle superior alveolar and anterior superior alveolar nerves (V2), arteries and veins.
VIII. Sublingual Gland A. Are the smallest of the paired salivary glands. B. Lie in floor of the mouth between the mandible and genioglossus muscle. C. Form horseshoe-shaped mass around frenulum of the tongue. D. Glandular tissue is innervated by parasympathetic fibers from the facial nerve. a. Preganglionic parasympathetic fibers emerge from facial as chorda tympani nerve. b. Chorda tympani nerve joins the lingual nerve (of trigeminal) in infratemporal fossa. c. Preganglionic fibers leave the lingual nerve and synapse on postganglionic parasympathetic cell bodies in the submandibular ganglion (ganglion suspended off the lingual nerve). d. Postganglionic parasympathetic fibers leave the ganglion to get back on lingual nerve and terminate in sublingual gland. Some fibers leave the ganglion and directly enter the submandibular gland. E. Postganglionic sympathetic fibers innervate blood vessels of the gland by traveling with the lingual artery.
IX. General Spaces of Oral Cavity A. Submandibular Space – Divided into Sublingual Space (above mylohyoid m.) and Submaxillary Space (below mylohyoid m. containing the main part of the submandibular gland). Note: To help understand this terminology, the mandible used to be called the submaxillary bone. Thus, the “submandibular gland” is synonymous with the “submaxillary gland” which was commonly used many years ago. Likewise, the submandibular ganglion was also referred to as the submaxillary ganglion many years ago. B. Lateral Pharyngeal Space – Lateral to buccinator muscle and lateral to anterior part of superior constrictor. The lateral pharyngeal space is potentially continuous with the retropharyngeal space (located posterior to the constrictors muscles of the pharynx). The retropharyngeal space in turn, is potentially continuous with the alar space (“danger space”). The alar space is located anterior to the vertebral bodies of the spinal column which we will also see in our dissection.
I. Functions of Larynx A. Phonation – Vibration of the true vocal cords (TVC) for voice production. B. Respiration – Adjustment of glottic aperture according to need. C. Swallowing – Protects upper airway.
II. Laryngeal Cartilages A. Thyroid Cartilage (unpaired): 1. Structurally consists of two lamina united anteriorly and with superior and inferior horns posteriorly. 2. Laryngeal prominence (Adams apple) is the protruding anterior-superior union of the two laminae. 3 Above the laryngeal prominence is the laryngeal (or thyroid) notch. 4. The oblique line identifies the insertion of the sternothyroid muscle and origin of the inferior constrictor muscle (inferiorly). 5. The oblique line identifies the inferior attachment of the thyrohyoid muscle (superiorly). 6. The inferior horns of the thyroid cartilage articulate with the sides of the cricoid cartilage. 7. Thyroid (as well as the cricoid and most of arytenoids cartilages) is composed of hyaline cartilage which later undergoes calcification.
B. Cricoid Cartilage (unpaired): 1. Shaped like a signet ring with an arch anteriorly and lamina posteriorly. 2. Only portion of the larynx and trachea that forms a complete ring around the airway. 3. Cricoid cartilage is attached to thyroid cartilage by the cricothyroid membrane, and the cricothyroid muscle. 4. Cricoid is attached to the trachea by the cricotracheal ligament which is a ligament similar in structure to the other annular ligaments of the trachea. 5. Adult at C6-C7, child at C3-C4.
C. Arytenoid Cartilages (paired): 1. Roughly shaped as a pyramid. a. Base – Cricoarytenoid joint (synovial). b. Anteriorly is vocal process – Attachment of vocal ligament. c. Lateral is muscular process – Insertion of PCAM and LCAM (muscles discussed later). d. Posteriorly – Attachment of oblique and transverse arytenoids muscles.
D. Epiglottis (unpaired): 1. Forms the anterior wall of the laryngeal aditus (entrance). 2. Inferior pointer is called petiolus. 3. Epiglottis contains numerous perforations and provides a poor barrier to disease. 4. Anterior-superiorly is glossoepiglottic folds (one median and two lateral) created by mucosal folding. Vallecula (little ditch) is the depressed space located between the folds (i.e., on right and left side of median glossoepiglottic fold). 5. Anterior region to epiglottis is clinically significant because epiglottis is a poor barrier to carcinoma.
E. Corniculate Cartilages (paired): 1. Small elastic cartilage on top of arytenoids cartilages. 2. Considered nonfunctional in the human.
F. Cuneiform Cartilages (paired): 1. Located within the aryepiglottic fold and of no significant importance.
G. Triticeal Cartilage (paired): 1. Small elastic cartilage embedded in the lateral region of the thyrohyoid ligament (posterior thickening of the thyrohyoid membrane). May calcify and be mistaken for a foreign body on an image.
A. Ossification 1. Thyroid cartilage: a. Occurs at 20-30 years of age. b. Begins at inferior margin and progresses cranially. 2. Cricoid cartilage: a. Ossifies after thyroid cartilage. b. Begins at superior margin and progresses caudally. 3. Arytenoid cartilage: a. Occurs at 30 years of age. b. Superior portion is elastic. 4. Hyoid cartilage: a. Ossifies from 6 centers. b. Starts at birth and complete by two years.
IV. Major Joints of the Larynx 1. Cricoarytenoid Joints (CAJ): a. Between cricoid and arytenoids cartilages. b. Synovial joint. Therefore contains capsule and synovial fluid for lubrication. c. CAJ allows for anterior and lateral as well as posterior and medial sliding of the arytenoid cartilage. In addition, when these movements are combined, the result is rotation of the arytenoid cartilage. 2. Cricothyroid Joints: a. Between cricoid and thyroid cartilages. b. Synovial joints (therefore has capsule and lubricating fluid). c. Permits slight rotation and gliding movement.
V. Major Ligaments and Membranes of the Larynx 1. Thyrohyoid Membrane: a. Membrane connecting the thyroid cartilage to the hyoid bone. b. Thickened at the midline and is called the median thyrohyoid ligament. c. Thickened at lateral most part (where membrane connects superior horn of thyroid cartilage to tips of greater horn of hyoid bone) and is called lateral thyrohyoid ligament.
57 2. Cricothyroid Attachments: a. Thick ligament located anteriorly called the anterior cricothyroid ligament that connects the cricoid cartilage to thyroid cartilage. b. Laterally the cricoid is attached to the inferior horns of the thyroid cartilage by the anterior inferior cricoid ligament and posterior superior cricothyroid ligaments. 3. Cricotracheal Ligament: a. Circular ligament (discontinuous posteriorly) linking cricoid to first trachea ring. 4. Ligaments of Epiglottis: a. Hyoepiglottic ligaments anchors epiglottis anteriorly to the hyoid bone. b. The pointer of the interior stalk is the petiolus and is anchored via the thyro- epiglottic ligament. 5. Vocal Ligament (True Cords): a. Extend from angle of thyroid cartilage anteriorly to the vocal process of the arytenoids cartilages posteriorly. b. Vocalis muscle is attached to ligament and lies parallel to the ligament. c. Directly involved with voice production and respiratory protection. 6. Quadrangular Membrane (located on interior of larynx): a. Two quadrangular sheets of elastic tissue which bridge the gap between the lateral border of the arytenoids and epiglottic cartilages. b. The superior border is free. c. The inferior limit is the weak vestibular ligament which supports the vestibular fold (forms the false vocal chords) 7. Conus Elasticus (located on interior of larynx): a. Is the lateral portion of the cricothyroid ligament. b. Specifically, elastic tissue arising from the cricoid cartilage runs superiorly to the vocal ligament and vocal process of the arytenoid. c. Anteriorly it forms part of the cricothyroid ligament. d. Collectively this tissue then forms an “elastic cone” from the vocal ligament down onto the cricoid cartilage.
VI. Interior Spaces of the Larynx 1. Vestibule – Between inlet and false cords (also called supraglottic area). 2. Ventricle of larynx – Deep spindle recess between false and true cords. a. Saccule – Conical pouch at anterior part of ventricle. i. Extends superiorly between the inner surface of thyroid cartilage and false cord. ii. Contains mucous glands and thought to lubricate the cords. iii. Enlargement of saccule is the source of laryngocele. 3. Glottis = true vocal folds and the rima glottidis (opening between true vocal folds). a. Anterior 3/5 composed of vocal ligament. b. Posterior 2/5 composed of vocal process. 4. Subglottic space – Below TVC and lower border of cricoid cartilage.
VII. Muscles of the Larynx
Primarily concerned with alterations in tension and length of the vocal cords in the production of voice and to facilitate or prevent the passage of air through the glottis. Also involved with protecting the laryngeal inlet. In general sound production occurs through adduction and tension adjustment of vocal fold/cord and respiration via abduction of the vocal fold.
58 All the laryngeal muscles are innervated by the vagus nerve (CN X).
Laryngeal muscles are divided into extrinsic and intrinsic muscles. Extrinsic muscles include the suprahyoid muscles (stylohyoid, digastric, mylohyoid and geniohyoid) which elevate the hyoid bone and larynx and the infrahyoid muscles (omohyoid, thyrohyoid, sternothyroid, and sternothyroid) which depress the hyoid bone and larynx. Inferior constrictor, which attached to the thyroid cartilage, is also considered an extrinsic laryngeal muscle. The intrinsic muscles are described below.
A. Cricothyroid Muscles (CTM paired): 1. Only muscle not innervated by the recurrent laryngeal nerve of vagus. 2. Innervated by the external laryngeal nerve (a branch of the superior laryngeal nerve of the vagus). 3. Originates from anterolateral part of cricoid cartilage. 4. Inserts on the inferior margin and inferior horn of the thyroid cartilage. 5. Action-Draws the arch of the cricoid posteriorly and thyroid cartilage anteriorly. This results in tightening and elongating the vocal cords. This is the primary tensor of the true vocal cord (TVC) and allows one to reach a higher note. B. Posterior Cricoarytenoid Muscle (paired): 1. Innervated by the recurrent laryngeal nerve. 2. Arises from posterior lamina of cricoid cartilage. 3. Inserts into the muscular process of the arytenoids cartilage. 4. Contraction pulls the muscular process posteriorly, medially and down, thereby sliding the arytenoids cartilage laterally and posteriorly to open (ABDUCT) the glottis. THIS IS THE ONLY ABDUCTOR OF THE GLOTTIS. C. Lateral Cricoarytenoid Muscle (paired): 1. Innervated by the recurrent laryngeal nerve. 2. Arises from the upper lateral border of the cricoid arch and the conus elastus. 3. Inserts on the muscular process of the arytenoid cartilage. 4. Contraction causes the muscular process to rotate anteriorly and laterally there by approximating (ADDUCTING) and classing the glottis. 5. Therefore, posterior and lateral cricoarytenoid muscle are antagonists. D. Transverse and Oblique Arytenoid Muscles (only unpaired muscles of larynx): 1. Innervated by the recurrent laryngeal nerve. 1. Fibers stretch between posterior surfaces of the two arytenoids cartilages. 2. Adduct glottis. E. Aryepiglottic Muscle: 1. Innervated by the recurrent laryngeal nerve. 2. Fibers from the oblique arytenoid muscles that extend from tip of arytenoid cartilage to the epiglottis. Basically, the anterior and superior extension of oblique muscles. 3. Constricts the laryngeal inlet or aperture. F. Thyroepiglottic Muscle: 1. Innervated by the recurrent laryngeal nerve. 2. Fibers of the thyroarytenoid arch posteriorly and superiorly to attach on the epiglottis. 3. Depress base of epiglottis. G. Thyroarytenoid Muscle: 1. Innervated by the recurrent laryngeal nerve.
59 2. Arises from lower internal surface of thyroid cartilage and extends posteriorly to insert onto the anterior surface of arytenoids cartilage. Runs parallel with and lateral to the vocal fold. 3. Reduces the distance between the arytenoids and thyroid cartilages, therefore relaxing or shortening the vocal ligament/folds. H. Vocalis Muscle (Thyroarytenoidus internus): 1. Innervated by the recurrent laryngeal nerve. 2. That portion of the thyroarytenoid that is spatially associated with the vocal ligament thus forming a bulk of the vocal fold.
VIII. Summary of Main Actions of Laryngeal Musculature A. Vary glottis: 1. Posterior* and lateral crico-arytenoids. 2. Transverse and oblique arytenoids (transverse and oblique) B. Regulate tension of vocal ligament: 1. Cricothyroid. 2. *Posterior cricoarytenoid 3. Thyroarytenoid (considered by some to be continuous with vocalis muscle). 4. Vocalis. C. Modify laryngeal inlet: 1. Aryepiglottic 2. Thyroepiglottic.
* Only abductor of glottis (i.e., open glottis), the rest of the muscles attached to the arytenoid cartilages adduct glottis (i.e., close glottis).
IX. Vasculature of Larynx A. Arterial Supply 1. Two arteries from external carotid. Both are branches from the superior thyroid artery. a. Superior laryngeal artery: i. Most important superior branch. ii. Runs horizontally across posterior portion of the thyrohyoid membrane. iii. Courses with the internal branch of the superior laryngeal nerve. iv. Penetrates the thyrohyoid membrane with the internal laryngeal nerve b. Cricothyroid artery: i. Branches off the superior thyroid artery and across the cricothyroid membrane. ii. Runs close to the inferior border of the thyroid cartilage. 2. Inferiorly, the larynx is supplied from one branch of the subclavian artery. a. Inferior Laryngeal Artery: i. Subclavian artery gives rise to the thyrocervical trunk. a. The thyrocervical trunk gives rise to the inferior thyroid artery. b. The inferior thyroid artery gives rise to the inferior laryngeal artery. c. The inferior thyroid artery lies in close association with the recurrent laryngeal nerve. d. Enters the larynx through the Killian-Jamieson area which is inferior to the inferior constrictor muscle (i.e., bounded superiorly by the
60 lowest cricopharyngeal fibers and inferiorly by the upper circular fibers of the esophagus). 3. There are numerous points of anastomosis of this arterial system beneath the mucosa lining of the larynx. 4. Veins follow the same general course as the superior and inferior thyroid arteries.
X. Lymphatics of the Larynx A. Large number of lymphatics throughout larynx except for the true vocal cords (TVC). B. Lymphatic drainage is divided by the TVC. C. The superior lymphatic’s drain through the floor of the pyriform recess with the superior laryngeal artery. The lymph then drains into the upper portion of the deep cervical (jugular) nodes. D. Inferior lymphatic’s drain into pretracheal (Delphian node) and into paratracheal (low deep cervical) nodes.
XI. Innervation of the Larynx: CN X, Vagus Nerve (both motor and sensory) A. Superior laryngeal nerve: a. Leaves the vagus nerve at the level of the inferior ganglion of the vagus (also known as the nodose ganglion). This ganglion contains pseudounipolar cell bodies (sensory type) that send fibers to provide general visceral sensation to larynx and taste sensation to pre-epiglottic region (via internal laryngeal nerve). b. Passes medial to external and internal carotids, then curves towards larynx. c. It then branches into external laryngeal nerve (smaller) and internal laryngeal nerve (larger). d. The external laryngeal nerve provides motor innervation to the cricothyroid muscle and contributes motor innervation to the inferior constrictor. The external laryngeal nerve usually accompanies the superior thyroid artery. e. The internal laryngeal nerve curves forward on the thyrohyoid membrane, accompanies the superior laryngeal artery, penetrates the thyrohyoid membrane and divides in several divisions. It provides sensory innervation to mucosa located superior to TVC to the inferior base of tongue. Therefore this nerve is only sensory. It also has special sensory fibers (taste) that innervate the region just anterior to the epiglottis (in the vallecula and posterior surface of tongue). B. Recurrent laryngeal nerve (inferior laryngeal nerve): a. Branches off vagus, curves around aorta on left side of body and curves around the subclavian artery on the right side of the body. It then courses superiorly within, or just lateral to, the tracheal esophageal groove. It assumes a close relationship to the inferior laryngeal artery. It courses under Berry’s ligament to enter the larynx with the inferior laryngeal artery through the space of Killian and Jamieson. b. Provides motor innervation to all intrinsic laryngeal fibers except the cricothyroid muscle (which is innervated by the external laryngeal nerve). c. Provides sensory innervation to laryngeal mucosa located inferior to TVC.
61 PTERYGOPALATINE FOSSA
I. General Information, Blood Supply, Venous Drainage, Nerve Supply (General Sensory and Autonomic)
A. Lies between pterygoid process of sphenoid bone and palatine bone.
B. Is bilateral (one on both sides of the head). The terms pterygopalatine fossa and sphenopalatine fossa are synonymous. Similarly, the terms pterygopalatine foramen and sphenopalatine foramen are synonymous. What is not interchangeable is the term fossa and foramen. Fossa refers to the large space between the sphenoid and palatine bones. The foramen provides the opening to the nasal cavity . We will use the terms pterygopalatine fossa and sphenopalatine foramen to distinguish the two. In addition, the sphenopalatine artery is commonly and clinically used to name for the artery that passes into the nasal cavity (through the sphenopalatine foramen).
C. Blood supply to the pterygopalatine fossa (PPF) is from the maxillary artery of the infratemporal fossa (which enters the PPF through the pterygomaxillary fissure).
D Venous drainage of the PPF is to the pterygoid plexus/maxillary vein (again through the pterygomaxillary fissure of the infratemporal fossa)
E. General sensory supply (pain, temp. touch) to the PPF is from maxillary nerve (V2) which enters the pterygopalatine fossa through the foramen rotundum of the middle cranial fossa (i.e., from behind - or posteriorly).
F. Autonomic supply to the PPF is from the nerve of the pterygoid canal. This contains both sympathetic (postganglionic) and parasympathetic (preganglionic) fibers. This nerve is also enters the PPF from behind (i.e., posteriorly). 1. Parasympathetic supply to the PPF: a. The facial nerve gives rise to the greater petrosal nerve in the petrous temporal bone. The greater petrosal nerve leaves the petrous temporal bone through the hiatus of the greater petrosal nerve to enter the middle cranial fossa. The greater petrosal nerve courses toward then enters the foramen lacerum. It continues inferiorly (to the bottom of the foramen lacerum) and enters the pterygoid canal where it changes its name to the “nerve in the pterygoid canal”. b. When the nerve (of the pterygoid canal) enters the pterygopalatine fossa preganglionic parasympathetic fibers end in the pterygopalatine ganglion (another parasympathetic ganglion in the head). The ganglion contains postganglionic parasympathetic cell bodies that give rise to
postganglionic parasympathetic fibers that join V2 (i.e., continue to the infratemporal fossa, nasal cavity, orbital cavity, oral cavity and pharynx -see below). 2. Sympathetic supply to the PPF: a. Sympathetic (preganglionic sympathetic) fibers arise from T1 of the thoracic spinal gray matter. The preganglionic sympathetic fibers ascend in the cervical sympathetic chain and end in the superior cervical (sympathetic) ganglion. Then, the superior cervical ganglion gives rise to postganglionic sympathetic nerves that form the internal carotid plexus (i.e., sympathetic nerves on the external wall of the internal carotid – also called by some “the internal carotid nerve”). The deep petrosal nerve emerges from the internal carotid plexus/nerve in the foramen lacerum where it joins the greater petrosal nerve (branch of CN VII –parasympathetics) to form the nerve of the pterygoid canal (also called the “Vidian nerve”). The nerve in the pterygoid passes through the pterygoid canal to reach the PPF. b. Once through the canal, the sympathetic nerves pass through the pterygopalatine ganglion (only the parasympathetic end in the ganglion.) and continue joining V2.
62 G. In summary, the PPF has: 1) blood supply and venous drainage from the maxillary artery and vein; 2) general sensory nerve fibers from V2 (the maxillary nerve); 3) parasympathetic nerve supply from the facial nerve (i.e., greater petrosal then nerve in the pterygoid canal) and finally; 4) sympathetic nerve supply from the internal carotid plexus (via superior cervical ganglion, deep petrosal nerve then nerve in the pterygoid canal).
H. It is important to note that the neurovascular bundles which leave the PPF (to the infratemporal fossa, nasal cavity, orbital cavity, oral cavity and pharynx) are functionally “fully equipped” neurovascular bundles. For example, they contain arterial supply (from maxillary artery) venous drainage (to maxillary vein), general sensory nerve fibers (via maxillary nerve (V2), postganglionic sympathetic nerve fibers (from superior cervical ganglion) and postganglionic parasympathetic nerve fibers (from the pterygopalatine ganglion).
II. Peripheral distribution of arteries, veins and nerves FROM the PPF.
A. Overall areas of distribution: 1. Infratemporal fossa (laterally via the pterygomaxillary fissure). a. posterior superior alveolar nerves to the upper teeth and gums. (Note maxillary artery and maxillary venous tributaries enter the pterygopalatine foramen through the pterygomaxillary fissure). 2. Nasal cavity (medially via the sphenopalatine foramen). a. sphenopalatine artery and vein and nerves of the nasal cavity gain access to the nasal cavity by passing through the sphenopalatine foramen . 3. Orbital cavity (anteriorly via the inferior orbital fissure). a. Infraorbital nerve, artery and veins pass through the infraorbital groove and canal give to off middle superior alveolar and anterior superior alveolar nerves and vessels. The infraorbital nerve and vessels eventually end, as they pass through the infraorbital foramen and emerge on the face below the orbital region. However, before passing through the infraorbital foramen, the infraorbital nerve also gives rise to several zygomatic nerve branches. Specifically, two sensory branches are given off which eventually become zygomaticofacial and zygomaticotemporal nerves (which must course through the zygomatic bone). Finally, a small branch arises from the zygomaticotemporal nerve (before it enters the zygomatic bone) which joins the lacrimal nerve (of V1) to provide parasympathetic fibers/innervation to the lacrimal gland. 4. Oral cavity (inferiorly to hard and soft palate via palatine canal then greater palatine and lesser palatine foramina). a. Descending palatine artery and vein along with the greater and lesser palatine nerves pass inferiorly in the palatine canal. The artery bifurcates. Then greater palatine nerves and vessels join and pass through the greater palatine foramen (to supply the hard palate). Similarly, lesser palatine nerves and vessels join and pass through the lesser palatine foramen (to supply the soft palate). 5. Pharynx (via pharyngeal canals). a. Arteries, veins and nerves from the PPF course posteriorly and inferiorly to supply the very top of the pharynx in and around the pharyngeal recess of the nasopharynx. Recall, most sensory fibers to the pharynx arise from the glossopharyngeal nerve (CN IX) via the pharyngeal plexus and most of the blood supply arises from the from the ascending pharyngeal artery.
B. Functionally, sympathetic nerve fibers supply blood vessels for vasoconstriction/vasodilatation purposes, whereas parasympathetic fibers innervate the mucous glands in the mucosal lining (i.e., mucosal membrane) and lacrimal gland. Nerve fibers from the trigeminal system provide pain, temperature and touch innervation to the target tissues. Finally, arteries and veins respectively, supply and return blood from these major regions.
C. Clinically, V2 can be anesthetized at its proximal location (i.e., near the foramen rotundum) through the
63 sphenopalatine foramen of the nasal cavity, the pterygomaxillary fissure of the infratemporal fossa and the greater palatine foramen of the oral cavity (i.e., hard palate). Nose bleeds can be controlled by applying pressure on the sphenopalatine foramen thus compressing the sphenopalatine artery.