1 ` 2019 Neuroanatomy Objectives
Cerebral Cortex
Cortical Lobes Frontal Lobe Parietal Lobe Occipital Lobe Temporal Lobe Limbic Lobe (Insula)
Major Cortical Fissures and Lobe Division Landmarks Central Sulcus (CS) Lateral Fissure (LF) Preoccipital Notch Parieto-occipital Fissure (POF)
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).
Summary of Major Functional Centers of the Cerebral Cortex Head and Neck Motor Control – Precentral Gyrus (M1), cranial nerves V, VII, IX, X, XII.
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
Brainstem
Diencephalon Thalamus (sensory relay to cortex and motor relay to cortex) Hypothalamus (basic physiologic drives and homeostasis) 3rd Ventricle
Midbrain Superior Colliculus (visual system relay) Inferior Colliculus (auditory system relay) Cerebral Aqueduct (Aqueduct of Sylvius)
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
Blood Supply of Central Nervous System Circle of Willis Anterior Communicating Artery Anterior Cerebral Artery Internal Carotid Artery Posterior Communicating Artery Posterior Cerebral Artery
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
CSF Circulation
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
Transverse Sinus
Sigmoid Sinus
Internal Jugular
Vein
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
A. Anterior cranial fossa- Formed by frontal bone (orbital plate), ethmoid bone (crista galli, cribriform plate) and the sphenoid bone (lesser wings). 1. Foramen: a. Cribriform plate - (for CN I)
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 anterior frontoethmoidal suture. Contains the anterior ethmoidal branch of the nasociliary nerve (V1), anterior ethmoidal artery, and anterior ethmoidal vein.
Carotid Canal
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.
Condylar Canal
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.
Foramen Lacerum
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.
Foramen Magnum
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.
Foramen Ovale
Located in the greater wing of the sphenoid bone. Contains the mandibular nerve (V3) lesser (superficial) petrosal nerve and accessory meningeal vessels.
Foramen Rotundum
Located in the greater wing of the sphenoid bone. Contains V2.
Foramen Spinosum
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.
Hypoglossal Canal
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.
Infra-Orbital Canal
Located on the anterior orbital surface of the maxilla. Contains the infra-orbital nerve, artery and vein.
Infra-Orbital Foramen
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).
8
Jugular Foramen
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.
Mandibular Foramen
Located on the inner surface of the ramus of the mandible. Contains the inferior alveolar nerve (from V3) and vessels.
Mental Foramen
Located on the outer surface of the body of the mandible usually below the second premolar tooth. Contains the mental nerve (a distal branch of V3) and vessels.
Mastoid Foramen
Located posterior to mastoid part of the temporal bone. Contains emissary vein linking occipital vein with sigmoid sinus.
Nasolacrimal Canal
Located at the anterior, lower medial border of the orbit formed by the lacrimal bone and maxilla. Contains the nasolacrimal duct.
Optic Foramen/Canal
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.
Petrotympanic Fissure
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).
Pterygoid Canal
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.
Pterygomaxillary Fissure
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).
Stylomastoid Foramen
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 medial aspect of the supra-orbital margin of the frontal bone. Contains the supraorbital nerve (from frontal nerve of V1) and vessels.
Zygomatico-Facial 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.
Zygomatico-Orbital Foramen
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).
Zygomatico-Temporal Foramen
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
General Information
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)
I. Mouth
- 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 orbi