Dissector Answers - Infratemporal Fossa & Oral Cavity

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Identify the masticatory muscles and give their functions.
  2. Define the boundaries and contents of the infratemporal fossa.
  3. Identify the branches of the trigeminal nerve and their functions related to mastication and sensation from the face.
  4. Identify the chorda tympani nerve and give its function.
  5. Describe the structure and function of the temporomandibular joint.
  6. Identify the muscles bordering the submandibular and paralingual spaces.
  7. List and identify the major nerves and vessels of these spaces.
  8. Describe the submandibular and sublingual salivary glands and give their innervations.
  9. List the muscles of the tongue and describe their origins.
  10. Describe the oral cavity, its oral vestibule and dental arches (including temporary and permanent dentitions), and the hard and soft palate.

Learning Objectives and Explanations:

1. Identify the masticatory muscles and give their functions. (N54A, N54B, N55, N69, N46, TG7-31, TG7-34, TG7-85)
Masseter muscle
Origin: Zygomatic arch
Insertion: Lower half of the mandibular ramus
Blood supply: Masseteric artery
Nerve supply: Masseteric nerve
Action: Mandibular elevation (powerful crusher of food)
Temporalis muscle
Origin: Temporal fossa, temporal fascia
Insertion: Coronoid process and temporal crest of the mandibular ramus
Blood supply: Anterior and posterior deep temporal arteries
Nerve supply: Anterior and posterior deep temporal nerves
Action: Elevation and retraction of the mandible
Medial pterygoid
Origin: Medial surface of lateral pterygoid plate
Insertion: Medial surface of the ramus of the mandible (below mandibular foramen)
Blood supply: Arterial twigs of the maxillary artery
Nerve supply: Nerve to medial pterygoid
Action: Protraction and elevation of the mandible
Lateral pterygoid
Origin: Upper head - base of the skull (greater wing of sphenoid); Lower head - lateral surface of lateral pterygoid plate
Insertion: Upper head - capsule and articular disc of the TMJ; Lower head - pterygoid fovea of the condylar neck
Blood supply: Twigs from the maxillary artery
Nerve supply: Short nerves from the mandibular division of the trigeminal nerve
Action: Protraction and opening movements of mandible
2. Define the boundaries and contents of the infratemporal fossa. (N4, N54A, N54B, ,N55, TG7-04A, TG7-32A, TG7-32B)
Boundaries:
Medial: Lateral pterygoid plate.
Lateral: Medial surface of the ramus of the mandible.
Anterior: Tuberosity of the maxilla.
Posterior: Deep part of the Parotid region.
Superior: Base of the skull (greater wing of sphenoid bone)
Inferior: Medial pterygoid muscle.
Contents:
Medial pterygoid muscle
Lateral pterygoid muscle
Maxillary artery and vein
Pterygoid plexus of veins
Mandibular division of trigeminal nerve
Otic ganglion
3. Identify the branches of the trigeminal nerve and their functions related to mastication and sensation from the face. (N45, N46, N122, TG7-29, TG7-81C, TG7-81D, TG7-85)
V1: Ophthalmic division
General sensory from the cornea, skin of forehead, scalp, eyelids, nose, and mucosa of nasal cavity and paranasal sinuses

V2: Maxillary division
General sensory from the skin of the face over the maxilla, including upper lip, maxillary teeth, mucosa of nose, maxillary sinuses, and palate

V3: Mandibular division (major nerve supply to masticatory muscles)
Sensory branches: Motor Nerves (to all masticatory muscles):
4. Identify the chorda tympani nerve and give its function. (N46, N123, TG7-37, TG7-84, TG7-88B)
Chorda tympani is a branch of the facial (CN VII) nerve that carries taste fibers from the anterior two-thirds of the tongue and joins the lingual nerve in the infratemporal fossa. In addition, the chorda tympani carries preganglionic parasympathetic fibers (secretomotor fibers) for the submandibular and sublingual salivary glands.
5. Describe the structure and function of the temporomandibular joint. (N14, TG7-32B, TG7-32C, TG7-33)
The TMJ is both a hinge and gliding synovial joint, with an articular disc present between the mandibular condyle and both the mandibular fossa and articular eminence on the temporal bone. With the fibrous capsule attaching to the perimeter of the articular surfaces and the edges of the articular disc, two articular cavities are formed. The upper one is between the articular disc and temporal bone, while the lower one is between the disc and mandibular condyle. The lateral and medial TM ligaments limit the posterior movements of the mandible. Movements involved include: hinge movement at the lower joint and gliding at the upper joint. The joint is innervated by the auriculotemporal nerve.
6. Identify the muscles bordering the submandibular and paralingual spaces. (N27, N28, N46, N53A, N53C, N59, N63, TG7-12, TG7-37A, TG7-37B, TG7-38)
MUSCLEORIGININSERTIONACTIONINNERVATIONNOTES
Digastric muscle, anterior belly digastric fossa of mandible body of hyoid via a fibrous loop over an intermediate tendon elevates and draws forward hyoid bone; depresses mandible mylohyoid nerve [from inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve (CN V3)] forms anterior boundary of submandibular triangle
Digastric muscle, posterior belly mastoid notch of temporal bone body of hyoid via a fibrous loop over an intermediate tendon elevates and retracts the hyoid bone; depresses mandible facial nerve (CN VII) forms posterior boundary of submandibular triangle
Stylohyoid posterior side of the styloid process splits around intermediate tendon of digastric to insert on the body of the hyoid bone elevates and retracts the hyoid bone facial nerve (CN VII) medial and parallel to posterior belly of digastric in submandibular triangle
Mylohyoid mylohyoid line of mandible midline raphe and body of the hyoid bone elevates the hyoid bone and tongue; depresses the mandible mylohyoid nerve [from inferior alveolar nerve, a branch of the mandibular division of the trigeminal nerve (CN V3)] paired mylohyoid muscles form the muscular floor of oral cavity
Geniohyoid mental spines of mandible body of hyoid bone elevates hyoid; depresses mandible C1 ventral ramus via fibers carried by hypoglossal nerve (i.e., ansa cervicalis fibers) adjacent to the midline and superior to mylohyoid
7. List and identify the major nerves and vessels of these spaces. (N46, N59, N122, N123, N126, N69, N70, TG7-18, TG7-19, TG7-40B, TG7-40C, TG7-81, TG7-84, TG7-94)
NERVE SOURCE BRANCHES MOTOR SENSORY NOTES
to mylohyoid inferior alveolar (from mandibular division of trigeminal, V3) none to mylohyoid m., terminates in anterior belly of digastric m. none arises near lingula of mandible (and often grooves the medial surface of the ramus)
lingual n. mandibular division of trigeminal, V3 none none general sensation to anterior two-thirds of tongue forms hammock for submandibular duct by crossing it twice in paralingual space
submandibular ganglion preganglionic parasympathetic from chorda tympani n. postganglionic parasympathetic to submandibular and sublingual glands secretomotor to submandibular and sublingual glands none hangs off lingual nerve just above deep part submandibular gland in the paralingual space
chorda tympani facial (CN VII) none secretomotor to submandibular and sublingual glands taste to anterior two-thirds of tongue indistinguishable from lingual nerve in submandibular and paralingual spaces
hypoglossal n. (CN XII) hypoglossal nucleus of medulla in brain none intrinsic and extrinsic muscles of tongue none only motor nerve to tongue


ARTERY SOURCE BRANCHES SUPPLY NOTES
facial external carotid a. ascending palatine a., tonsilar br., submental a., superior and inferior labial as., lat. nasal br., angular a. lower part of palatine tonsil, submandibular gland, facial muscles, & fascia deep to submandibular gland
submental facial a. none sublingual gland, submental triangle none
lingual external carotid a. suprahyoid br., dorsal lingual brs., deep lingual a., sublingual a. tongue, suprahyoid muscles, palatine tonsil runs deep to hyoglossus m.
deep lingual lingual a. none anterior tongue terminal branch of lingual a. from bifurcation deep to hyoglossus m.
sublingual lingual a. none sublingual gland, mylohyoid m. mucous membranes of floor of mouth terminal branch of lingual a. from bifurcation deep to hyoglossus m.


VEIN TRIBUTARIES DRAINS INTO REGION DRAINED NOTES
facial vein submental vein, others common trunk for lingual, facial, retromandibular vs., then internal jugular submandibular gland and others superficial to submandibular gland
submental vein none facial v. submandibular triangle anterior to submandibular gland, including sublingual gland
vena comitans of the hypoglossal n. deep lingual v., sublingual v. lingual v. tongue, sublingual region accompanies CN XII, usually inferior to n., runs on hyoglossus m.
8. Describe the submandibular and sublingual salivary glands and give their innervations. (N46, N61, N123, N133, TG7-31, TG7-37, TG7-40, TG7-84)
Submandibular gland: This salivary gland occupies most of the posterior part of the submandibular triangle. The superficial portion is larger and lies inferior to the mylohyoid muscle directly underneath the superficial layer of cervical fascia. The deep portion folds around the posterior edge of the mylohyoid muscle to lie deep in the sublingual space between the mylohyoid and hyoglossus muscles. The 5 cm long submandibular duct arises from the deep part of this gland and passes forward and medialward to open in the sublingual caruncle at the side of the lingual frenulum. The facial artery and vein supply this gland, and lymphatic drainage is to the submandibular lymph nodes.

Innervation of submandibular gland:
Sublingual gland: This is the smallest salivary gland. It is located beneath the oral mucosa in the floor of the mouth between the mandible on one side and the genioglossus and hyoglossus muscles on the other side. The sublingual gland sits on the mylohyoid muscle. Unlike the submandibular gland, which drains via one large duct, the sublingual gland drains via approximately 12 small ducts along the sublingual fold along the floor of the mouth. (This occurs basically in a line behind the sublingual caruncle.) Blood supply is from the sublingual branch of the lingual artery and from the submental branch of the facial artery.

Innervation of the sublingual gland: Same as the submandibular gland.
9. List the muscles of the tongue and describe their origins. (N53A, N53C, N59, N63, N68, N126, TG7-40, TG7-38)
MUSCLEORIGININSERTIONACTIONINNERVATIONNOTES
Hyoglossus body and greater horn of the hyoid bone intrinsic muscles of the tongue depresses side of tongue; retracts tongue hypoglossal nerve (CN XII) this extrinsic muscle of the tongue lies in submandibular triangle
Genioglossus mental spine on inner aspect of mental symphysis fans out to insert into the tongue from tip to base inferior fibers protrude tongue; middle fibers depress tongue; superior fibers draw tip back and down hypoglossal nerve (CN XII) this extrinsic muscle of the tongue is fan shaped and lies vertically next to the median plane
Styloglossus styloid process side of the tongue retracts and elevates tongue hypoglossal nerve (CN XII) this extrinsic muscle runs longitudinally along the side of the tongue
Superior longitudinal base of tongue apex of tongue hypoglossal nerve (CN XII) intrinsic muscle immediately under mucous membrane of dorsum
Inferior longitudinal base of tongue apex of tongue hypoglossal nerve (CN XII) intrinsic muscle runs between genioglossus and hyoglossus on inferior surface of tongue
Transverse lingual septum of tongue submucous tissue at side of tongue compresses sides of tongue; shapes tongue for speech and mastication hypoglossal nerve (CN XII) intrinsic muscle runs transversely between superior and inferior longitudinal layers
Vertical superior surface of tongue inferior surface of tongue shapes tongue for speech and mastication hypoglossal nerve (CN XII) intrinsic muscle with fibers at border of tongue
10. Describe the oral cavity, its oral vestibule and dental arches (including temporary and permanent dentitions), and the hard and soft palate. (N56, N57A, N57B, N63, TG7-38, TG7-32)
The oral cavity extends from the lips to the palatopharyngeal folds. The oral vestibule lies between the lips and the teeth.

The dental arches, upper and lower, are made, on each side, of 2 incisors, 1 canine, 2 premolars, and 3 molar teeth for the permanent dentition, and 2 incisors, 1 canine, and 2 molars for the temporary or deciduous dentition.

The hard palate is formed primarily by the palatine processes of the maxillary bones, with the horizontal processes of the palatine bones forming the posterior third. The soft palate stretches posteriorly. It is a fibromuscular septum that can be moved to close off the nasopharynx.

Questions and Answers:

12. Can you find the deep temporal nerves and arteries? (N46, N69, TG7-34, TG7-85)
They should be present innervating and feeding the temporalis muscle, respectively. The anterior and posterior deep temporal arteries are branches of the maxillary artery, and their accompanying nerves are branches of mandibular division of trigeminal.
13. What is the articular eminence? (N14, TG7-06)
The articular eminence is a projection of bone at the anterior margin of the mandibular fossa.
14. Consider the condylar movements at each (joint cavity formed by the articular capsule). (N14, TG7-33)
See above, but briefly:
Hinge movement at the lower joint (initiation of mandibular opening)
Gliding at the upper joint (termination of mandibular opening).
15. What kind(s) of fibers does it (chorda tympani) carry? (N46, N123, TG7-84)
See above, objective 4.
16. Identify other branches of the mandibular division of the trigeminal, a mixed motor and sensory nerve. (N46, TG7-84A, TG7-84B, TG7-84C, TG7-84D, TG7-85A, TG7-85B)
See above, objective 3.
17. Accompanying autonomic fibers? Otic ganglion? (N46, N125, TG7-84)
The autonomic fibers from the chorda tympani were mentioned above (objective 4). Other fibers present involve the otic ganglion. Specifically, this structure is a parasympathetic ganglion just below the foramen ovale, which receives preganglionic parasympathetic fibers from the glossopharyngeal nerve (CN IX) via the lesser petrosal nerve. Postganglionic parasympathetic fibers emerging from the ganglion join the auriculotemporal nerve and reach the parotid gland.
18. Define the boundaries of the submandibular triangle. (N28, TG7-02, TG7-12)
The submandibular triangle is defined by the inferior border of mandible and the anterior and posterior bellies of digastric muscle. Please note that the submandibular triangle is the "suprahyoid portion of the anterior cervical triangle" (W&B 213)
19. Trace the facial artery and vein noting relations with the submandibular gland (which one is superficial or deep to the gland?). (N69, N70, TG7-19)
The facial artery is deep to the superficial portion of the submandibular gland. The facial vein crosses the superficial surface of the submandibular gland
20. Can you find the mylohyoid nerve? (N46, TG7-85)
The mylohyoid nerve arises from the inferior alveolar nerve, which is in turn a branch of the mandibular division of the trigeminal nerve (CN V3). It arises near the lingula of the mandible. The inferior alveolar nerve continues its course through the mandibular foramen, but the mylohyoid nerve stays on the medial surface of the mandible. This makes the nerve readily identifiable, as it is plastered to the inside of the mandible.
21. Locate the mylohyoid nerve (what muscles does it supply; what does it arise from?) (N46, TG7-85)
The mylohyoid nerve supplies the mylohyoid muscle before burying itself in the anterior belly of the digastric muscle.
22. On the tongue, identify the foramen cecum (significance?). (N58, TG7-39)
The foramen cecum is a small pit on the dorsum of the tongue located in the midline. It is at the apex of the sulcus terminalis. It is an embryological remnant marking the site of the diverticulum of the thyroid gland, the thyroglossal duct.
23. Where is the lingual tonsil? (N58, N63, TG7-39)
The lingual tonsil is in the submucosa on the superior surface of the root of the tongue just behind the sulcus terminalis. It is a collection of lymphoid nodules that give the posterior one-third of the tongue its warty appearance.
24. Consider the motor and sensory (special and general) innervation of the tongue. (N62, N126, TG7-39, TG7-90, TG7-94)
GENERAL SENSATIONTASTE (SPECIAL SENSATION)MOTOR
ANTERIOR TWO-THIRDSLingual n. (V) Chorda tympani (VII) Hypoglossal n. (XII) -- extrinsic and intrinsic muscles
POSTERIOR ONE-THIRDGlossopharyngeal n. (IX) Glossopharyngeal n. (IX) (includes vallate papillae)
EPIGLOTTIC REGION OF TONGUE Superior laryngeal n. (X) Superior laryngeal n. (X), internal branch
25. Read about the intrinsic muscles of the tongue. (N126, TG7-38)
These are all muscles with attachments entirely within the tongue. Like all true tongue muscles (intrinsic and extrinsic), they are innervated by the hypoglossal n. (CN XII). They are the superior longitudinal muscle, the inferior longitudinal muscle, the transverse lingual muscle, and the vertical muscle. All are treated in more detail in the objectives section (but the only thing that I think we need to be aware of according to the laboratory manual is that intrinsic muscles, as a group, exist).
26. Consider actions of both intrinsic and extrinsic groups of muscles in moving the tongue and changing the shape of the organ. (N53A, N53C, N59, N63, N68, N126, TG7-38, TG7-40)
The actions of the extrinsic muscles are covered in the objectives section. In addition, the palatoglossus, which is not a true tongue muscle, assists in elevation of the tongue. The intrinsic muscles assist in all of the actions of the tongue but are particularly involved in deviations of the tongue from side to side. Note that extrinsic and intrinsic muscles combine for all of the actions of the tongue. "In eating, the tongue forms itself into a trough-like receptacle, conducts the food between the teeth for their tearing and crushing actions, and prevents food from falling to the floor of the mouth. Finally it makes firm pressure against the palate above and forces the mixed food and saliva into the oropharynx" (W&B 276).