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

Readings and Modules:

Procedure:

1. Review the osteology of the infratemporal fossa and oral cavity. (Play movie; View images: N 4A, 4B, 6, 8, 11, 12, 13A, 13B, 14, TG 7-04, 7-06, 7-07, 7-08, 7-32A, 7-32B, 7-32C)

On the skull, identify the articular eminence, mandibular fossa, lateral and medial pterygoid plates, pterygomaxillary fissure, foramen ovale, foramen spinosum and styloid process. On the mandible, identify the mandibular notch, coronoid process, condyle, pterygoid fovea, neck, lingula, mandibular foramen, mylohyoid line, and mental spines.

2. On the right side, reflect the masseter and zygomatic arch downward toward the angle of the mandible. (Play movie; View images: N 15, 23, 24, 25, 46, 54A, 54B, 69, 70, TG 7-31A, 7-31B, 7-32B, 7-32C, 7-34, 7-35, 7-36, 7-71, 7-73, 7-75, 7-84)

On the right side of the head, make a vertical incision through the parotid gland and turn it forward, detaching it from the masseter muscle. The incision should parallel the posterior border of the ramus of the mandible. Observe the cut facial nerve and the retromandibular vein within the gland.

Skin the temporal fossa and expose the temporal fascia. Review the superficial temporal artery and vein and the auriculotemporal nerve (V3). Completely remove the temporal fascia and clean the temporalis muscle noting different directions of the muscle fibers. Locate and trace the buccal nerve (V3) as it passes through the inserting fibers of temporalis to distribute to the skin of the cheek and oral mucosa.

Below the zygomatic arch, clean the masseter muscle. Cut the zygomatic arch by sawing through it just in front of the articular eminence and as far forward as possible on the zygomatic bone. Reflect the masseter and arch together toward the angle of the mandible. Locate the nerve to masseter emerging through the mandibular notch and cut it as you reflect the masseter inferiorly.

Now, saw through the base of the coronoid process and reflect all of the temporalis muscle upward. Can you find the anterior and posterior deep temporal nerves and arteries?

3. Remove the ramus of the mandible by sawing through the neck of the condyle and clipping the ramus above the mandibular foramen. (Play movie; View images: N 15, 46, N55, TG 7-32B, 7-32C, 7-34, 7-37)

Next, to get access to the infratemporal fossa, saw through the base of the neck of the condyle. Then, use the bone clippers to carefully remove the mandibular ramus down to the mandibular foramen, taking care to identify and preserve the inferior alveolar neurovascular bundle entering the mandibular foramen. Continue to preserve the inferior alveolar neurovascular bundle as the entire ramus of the mandible is removed down to the angle.

4. Clean the lateral and medial pterygoid muscles, examine the temporomandibular joint, remove the condyle of the mandible and lateral pterygoid muscle to expose the branches of the trigeminal nerve and the maxillary artery. (Play movie; View images: N 4, 15, 16A, 16B, 46A, N46B, N53, 55, 69, 70, 125, 133, TG 7-06, 7-32A, 7-32B, 7-32C, 7-34, 7-35, 7-36, 7-37, 7-73, 7-84, 7-90)

Clean the lateral pterygoid muscle. Note its two heads and different attachments. While cleaning it, carefully expose the maxillary artery and define its course (is it superficial or deep to the muscle?).

Examine the temporomandibular joint (TMJ) by cutting its capsule open. Identify the articular disk and the two articular compartments. What is the articular eminence? Consider the condylar movements at each compartment. Note the attachment of the upper head of the lateral pterygoid muscle to the disc and the lower head to the pterygoid fovea of the mandible. Now, completely remove the condyle and neck with the attached disc and lateral pterygoid muscle. Examine the disc and note its shape, thickness and attachment of the upper head. Examine the mandibular condyle, and note depth of of the mandibular fossa. If the maxillary artery courses deep to lateral pterygoid muscle, you will now be able to clean it fully.

Motion at the temporomandibular joint

Trace the maxillary artery toward the pterygomaxillary fissure. Identify the middle meningeal, inferior alveolar, buccal, and muscular branches to masseter, temporalis, and medial and lateral pterygoid muscles. Remove the pterygoid plexus of veins and note the maxillary vein.

Identify the lingual and inferior alveolar nerves and trace them toward the foramen ovale. Identify the auriculotemporal nerve passing medial to the mandibular fossa. Note the chorda tympani joining the lingual nerve from behind. What kind(s) of fibers does it carry? Identify other branches of the mandibular division of the trigeminal, a mixed motor and sensory nerve. Accompanying autonomic fibers? Otic ganglion?

Clean the lateral surface of the medial pterygoid muscle and review its attachments.

Muscles of the infratemporal fossa

5. Clear the deep cervical fascia and expose the submandibular gland, the digastric, and mylohyoid muscles and facial artery. (Play movie; View images: N 24, 27, 28, 46, 53A, 53C, 59, 61, 63, 69, 70, 71, TG 7-12, 7-17, 7-18, 7-19, 7-31, 7-34, 7-35, 7-37A, 7-37B, 7-40A, 7-40B)

On both sides of the face, define the boundaries of the submandibular triangle. Clear the superficial layer of deep cervical fascia and expose the submandibular gland, the digastric muscle (its anterior and posterior bellies), the mylohyoid muscle and the stylohyoid muscle.

Surface structures of the oral cavity
Teeth
Muscles of the oral cavity

Trace the facial artery and vein in the neck, noting relations with the submandibular gland (which one is superficial or deep to the gland?). Locate the mylohyoid nerve (what muscles does it supply; what does it arise from?).

Examine the submandibular gland, its extent within the submandibular triangle and its deep part that hooks around the posterior border of the mylohyoid muscle.

On the right side only, carefully sever the insertion of the stylohyoid muscle and the attachment of the digastric tendon from the hyoid bone and reflect these muscles. Note the hypoglossal nerve and its vena comitans passing deep to the posterior border of the mylohoid muscle. Now sever the origin of the mylohyoid muscle from the mandible and reflect it down toward the hyoid bone. Identify the hyoglossus muscle and trace it from its hyoid bone origin into the tongue. Now identify the lingual artery at its origin from the external carotid artery, and trace it until it passes deep to the hyoglossus muscle to supply the tongue.

6. On the left side of the head, incise the mucous membrane of the floor of the mouth to expose the paralingual space. (Play movie; View images: N 51, 7-38 shows you roughly the area where you need to make a cut beside the tongue. Plates 51A, 51B, 58, TG 7-37, 7-38B, 7-38C)

Incise the mucous membrane of the floor of the mouth next to the tongue, being careful to not cut too deeply. Identify, but don't cut, the palatoglossal fold. Carefully reflect the mucous membrane laterally to expose the contents of the paralingual space.

7. Examine the sublingual gland, the lingual and hypoglossal nerves, the submandibular ganglion and submandibular duct. (Play movie; View images: N 46, 51, 53, 59, 61, 69, 126, TG 7-37A, 7-37B, 7-38, 7-84, 7-88)

On the right side, incise the oral mucosa in the floor of the mouth and flip the mandible up to expose the paralingual space. Be careful not to cut the lingual nerve.

On both sides, identify the following structures:

  1. Sublingual gland, the smallest of the salivary glands.
  2. Submandibular duct courses anteriorly against the medial surface of the sublingual gland and opens onto the sublingual caruncle.
  3. Lingual nerve (V3), in the paralingual space, passes lateral and then inferior to the submandibular duct and has the submandibular ganglion (parasympathetic) attached to it.
  4. Deep portion of the submandibular gland, from which extends the submandibular duct.
  5. Hypoglossal nerve, the most inferiorly located element in the paralingual space.

8. Examine the tongue, identifying its parts, intrinsic and extrinsic muscles. (Play movie; View images: N 53A, 53C, 56, 57A, 57B, 58, 59, 62, 63, 68, 126, TG 7-20, 7-32, 7-38, 7-39A, 7-39B, 7-40, 7-94)

On the tongue identify the foramen cecum (significance? ), and the row of vallate papillae. Where is the lingual tonsil? Identify the extrinsic muscles of the tongue: genioglossus, hyoglossus, and styloglossus muscles. Consider the motor and sensory (special and general) innervation of the tongue. Read about the intrinsic muscles of the tongue. Consider actions of both groups of muscles in moving the tongue and changing the shape of the organ. Identify the geniohyoid muscle lying between the mylohyoid and the genioglossus muscles.

In the mouth, examine the gingiva (gums). Identify central and lateral incisors, canines, first and second premolars, and the first, second, and third molars, if present. What are deciduous teeth? Distinguish between oral cavity proper and the vestibule.

Skull structures
Cranial structures