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Learning Outcomes

• The • The Submandibular – Surface Anatomy Region – Muscle Attachments – Submandibular Gland Submandibular Region • The Floor of the Mouth – (FOM) – Lingual – Muscles of the FOM • The Head & Mohammed A Al-Muharraqi MBChB, BDS, MSc, MRCS Glas, FFD RCS Irel, MFDS RCS Eng • The Parasympathetics – Muscles of the Tongue

e-mail: [email protected]

Mandible Mandible Head of Condylar Process Coronoid Process Neck of Neck of Condylar Condylar Process Condylar Process Ramus of Mandible Process Condylar Process Anterior Border of Ramus Lingula Coronoid Process Mandibular Coronoid Lingual (Genial) Foramen (Mandibular) Foramen Notch Alveolar Ridge Oblique Line Alveolar Ridge Posterior Border of Ramus of Mandible Ramus Angle of Mandible Incisive Fossa

Mylohyoid Groove Angle of Mandible

Symphysis Menti (Median Ridge) Inferior Border of Submandibular Fossa Body of Mandible Body

Sublingual Fossa Digastric Fossa

Mental Foramen Superior Inferior Mental Spine (Genial Tubercle) (Genial Tubercle) Inferior Border of Body

Muscle Attachments The mental tubercle (a raised prominence at Mandible Ligaments the mental symphysis) is a point of muscular attachment. The external surface of the ramus is covered by the attachment of the . On the inner surface of the body of the mandible, there is a horizontal mylohyoid line, which attaches the . Above it, there is a shallow depression for the sublingual and below it a deeper depression for the submandibular gland. At the anterior ends of the mylohyoid lines and superior to them, near the symphysis, there is the genial tubercles. Geniohyoid and attach here. The inner surface of the mandibular ramus is where the attaches. The sphenomandibular ligament attaches to the lingula (and superiorly to the sphenoid spine). The coronoid process is a triangular protuberance from the anterosuperior surface of the ramus. The temporalis muscle attaches here, predominantly on the deep surface. The condylar process is one of the important attachments for the .

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The hyoid is situated at the level of the third cervical vertebra and is suspended from the styloid Floor of the Mouth processes of the temporal by the stylohyoid ligaments. The bone is horseshoe-shaped and consists of Inferior Border of Mandible a central body spanning the midline, with greater and lesser horns on each side. Muscles attached to the are: genio-glossus, genio-hyoid, hyo- First Cervical Vertebra glossus, chondro-glossus, middle (Atlas) constrictor of the , mylo- hyoid, omo-hyoid, sterno-hyoid, stylo-hyoid, thyro-hyoid and the levator of the thyroid gland. Hyoid Bone Ligaments attached to the hyoid bone are: stylo-hyoid ligaments, Thyroid Cartilage thyro-hyoid membrane, hyo- Cricoid Cartilage epiglottic ligament, lateral thyro- hyoid ligaments and the median thyro-hyoid ligament. Clavicle

The originates Genioglossus lies anteriorly near the from the inferior genial tubercle, median plane. It originates from the found on the back of the symphysis superior genial tubercle (mental spine) Floor of the Mouth menti of the mandible, the mental Floor of the Mouth on the mandible. It fans out into the Submandibular Hypoglossal Ganglion Nerve spine of the mandible. It passes substance of the tongue. The superior backwards and slightly downwards fibers of the genioglossus muscle pass Tongue to insert onto the anterior surface upwards and anteriorly towards the Facial on the body of the hyoid bone’s tip of the tongue. Genioglossus body. The innervation is shared Transverse & Vertical receives its motor innervation from Lingual Muscles Facial with the thyrohyoid muscle, namely the . The lingual the first cervical spinal nerve Genioglossus artery and the submental branch of Sublingual Gland traveling with the hypoglossal the facial artery supply this muscle. Geniohyoid nerve. The blood supply is derived Geniohyoid The genioglossus muscle is a from the (sublingual protractor and depressor of the Mandibular branch). The geniohyoid muscle tongue. Internal Jugular Nerve (VII) Median Thyroid Vein elevates the hyoid bone and is a Ligament Styloglossus arises from the tip of the Thyrohyoid weak depressor of the mandible. Thyrohyoid styloid process and the . The Cricothyroid Cricothyroid longitudinal & oblique parts of the Accessory Common Carotid muscle blend with the inferior Nerve longitudinal muscle of the tongue. It Thyroid Gland continues forwards towards the tip of the tongue. It is supplied by the hypoglossal nerve. The sublingual branch of the lingual artery supplies the muscle. Styloglossus retracts and elevates the tongue.

The consists of an The mylohyoid muscle arises from anterior belly and a posterior belly the mylohyoid line of the mandible. connected by an intermediate tendon. The anterior fibers of the mylohyoid The anterior belly is attached to the Floor of the Mouth Floor of the Mouth muscle interdigitate with the digastric fossa on the inferior border of corresponding fibers on the Mylohyoid the mandible. It runs downwards and Mylohyoid Tongue backwards to the digastric tendon. It Tongue opposite side to form a median develops from the first branchial arch raphe. This raphe is attached above Facial Facial to the symphysis menti of the Vein and so receives its motor supply from Vein Levator of the the mandibular division of the Levator of the mandible and below to the anterior Thyroid Gland Facial . It receives its blood Thyroid Gland Facial surface of the hyoid bone. The Artery Artery supply from the submental branch of mylohyoid branch of the the facial artery. The posterior belly Sublingual Gland mandibular division of the Anterior Belly of arises from the mastoid (digastric) Digastric Submandibular trigeminal nerve supplies the notch behind the mastoid process. The Gland muscle. The mylohyoid muscle Mandibular posterior belly passes to the hyoid bone Mandibular Internal Jugular Nerve (VII) where it becomes the intermediate Internal Jugular Nerve (VII) receives its arterial supply from the Vein Vein sublingual branch of the lingual Superior Belly digastric tendon. The posterior belly of Thyrohyoid of Omohyoid the digastric develops from the second artery, the , the branchial; hence its innervation is mylohyoid branch of the inferior Sternohyoid Cricothyroid derived from the the facial nerve. Its alveolar artery, and the submental Accessory arterial blood supply is from the Accessory Common Carotid branch of the facial artery. It raises posterior auricular and occipital Nerve Sternothyroid Nerve Sternothyroid the floor of the mouth during the . Thyroid Gland first stages of and helps Inferior Belly The digastric muscle is involved in of Omohyoid maintaining the stability of the hyoid to depress the mandible when the bone and helps to raise the hyoid bone hyoid bone is fixed. Conversely, it and the base of the tongue, but its aids in elevation of the hyoid bone . prime function is to assist in depressing and retracting the mandible.

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Nerve Supply to the Tongue

The Tongue

Hypoglossal Nerve (CNXII) and Muscles of the Tongue Brainstem: Pons Lingual Artery Cerebellum Brainstem: Medulla Hypoglossal Oblongata The lingual artery is the main blood supply Nerve Root Cervical Ventral Nerve Root of the tongue, arising from the external Superior Longitudinal carotid artery and coursing deep to Lingual Muscles (CNXII) . It branches extensively within Transverse & Vertical Lingual Muscles the tongue. When resecting the tongue Styloid Process (CNXII) Genioglossus haemorrhage is more marked in the Spinal Accessory Nerve Inferior Longitudinal Lingual Muscles (CNXII) posterior region. Hence laser surgery or (CNXII)

diathermy techniques are preferred. Styloglossus Symphysis Menti Venous drainage is by the lingual vein (CNXII) (Median Ridge) Hyoglossus (superficial to hyoglossus), draining to the (CNXII) internal . The lingual may be seen easily on the underside of the tongue, running just beneath the mucosa. These veins tend to become more prominent with age.

*Hypoglossal Nerve (XII) Hyoid Bone Geniohyoid

Hyoglossus The hyoglossus is a thin, quadrilateral muscle, which provides an important landmark in the floor of the mouth. It originates from the superior border of the greater horn of the hyoid bone. A part of the muscle is attached to the base of the lesser horn of the hyoid bone and has been called ‘’. At its origin, the hyoglossus muscle is separated from the attachment of the middle constrictor muscle of the pharynx by the lingual artery. It passes vertically upwards to insert into the side of the tongue. The hypoglossal nerve supplies the hyoglossus muscle. The sublingual branch of the lingual artery and the submental branch of the facial artery supply hyoglossus. Hyoglossus depresses the tongue. The and crosses hyoglossus as it forms the floor of the submandibular fossa. It is a key landmark in submandibular gland surgery.

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Muscles of the Tongue Hyoglossus (CNXII)

Intrinsic Lingual Muscles (CNXII)

Genioglossus (CNXII)

Symphysis Menti (Median Ridge)

Mylohyoid Hyoid (CNV) Bone Geniohyoid Lingual Artery Hypoglossal Lingual Nerve (C1 on XII) Hyoid Bone Nerve (XII)

All Muscles Are supplied by: Except: Which is/are supplied instead by: of: Stylopharyngeus Glossopharyngeal (IX) Pharynx Pharyngeal plexus (IX, X, symp) Cricopharyngeus Recurrent laryngeal

Palate Tensor palati Off n to med pterygoid (Vc) Pharyngeal plexus

Tongue Hypoglossal (XII) Palatoglossus Pharyngeal plexus

Mastication Mandibular (Vc) Buccinator Facial (VII)

Recurrent laryngeal Cricothyroid Ext br of superior laryngeal (X) (X)

Facial Oculomotor (III) & sympathetic expression & Facial (VII) Levator palpebrae buccinator superioris Superior oblique Trochlear (IV) Eye Oculomotor (III) Lateral rectus Abducent (VI)

Strap group Ansa cervicalis Thyrohyoid C1 fibres on hypoglossal

Sublingual Gland Sublingual Gland

When saliva is retained or is extravasated The paired sublingual glands are about into the adjacent tissues, mucocoeles twice the size of an almond. They are (salivary cysts) appear. In the floor of the mainly mucous and have over a dozen mouth they are called a ranula because they ducts, half of which open into the look like the belly of a frog. submandibular gland and half of which

Excessive salivation (sialorrhoea) may appear open into the sublingual papilla directly. in patients who have little lip control such as stroke patients or by parasympathetic It lies in front of the anterior border of stimulation. Conversely, sympathetic hyoglossus, between mylohyoid and stimulation such as in the fight or flight genioglossus and makes a superficial response or by sympatheticomimetic drugs depression in the mandible. such as hyosine (used in motion sickness) causes a dry mouth.

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Submandibular Gland The submandibular gland is subject to all the Submandibular Gland diseases of the salivary glands including stones The submandibular gland is irregularly shaped and that form by precipitation on epithelial debris. about 2 x 3 x 3 cm in size. The gland consists of a larger They are not always calcific and so do not always superficial part and a smaller deep part. The two are appear on radiographs. However, sialography, continuous as they wrap around the posterior free when a dye is introduced into the gland, will edge of the mylohyoid muscle. The submandibular reveal any blockage. gland extends anteriorly as far as the anterior belly of The incision for removal of the gland must also the digastric and posteriorly as far as the stylomandibular ligament. Laterally, it lies within the be at least one finger's breath inferior to the submandibular fossa on the medial surface of the lower border of the mandible to avoid damage to mandible. The submandibular (Wharton's) duct is 4 to the mandibular branch of the facial nerve. Having 5 cm long. It leaves the deep part of the gland, runs incised platysma, the facial veins are the next anteriorly on the surface of hyoglossus (and deep to obstacle. They are usually ligated and cut. the mylohyoid), and terminates at the sublingual Occasionally the facial artery requires ligation. It papilla in the floor of the mouth. The submandibular is important to tie off both ends securely as the duct is accompanied by the lingual nerve the external artery can bleed from both points due to multiple surface of hyoglossus. The lingual nerve is crossed by anastomoses along its length. Finally care must be the duct superiorly on its way into the hyoglossus, taken to identify the duct correctly and avoid hence the rhyme: damage to the lingual nerve. It is extremely important to identify the duct correctly before The lingual nerve takes a swerve, cutting it, because severing the lingual nerve will Around the hyoglossus, cause parasthesia of the anterior two thirds of the Says Wharton's duct to the nerve, "I think I'm going to cross it!" tongue which may not fully recover.

The Parasympathetic Ganglia in the Head

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End

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