Prelab Images - Infratemporal Fossa & Oral Cavity

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

1. Review the osteology of the infratemporal fossa and oral cavity. (Play movie)

Plates N12, N14, TG7-06 show the articular tubercle or eminence (it is the anterior part of the mandibular fossa). Plates N4 , TG7-04, TG7-06, N12 show the mandibular fossa. Plates N6, TG7-08, N8, TG7-06 identify the medial and lateral pterygoid plates. Plate N4, TG7-32 labels the pterygomaxillary fissure. The foramen ovale can be seen in plates N4, N8 and N11 or TG7-06, TG7-07. The foramen spinosum can be seen in plates N8, TG7-06, N11, TG7-07. Plates N4, TG7-04, N13 , TG7-32 show the styloid process. Plate N13, TG7-32B, TG7-32C show the mandible and its features: mandibular notch, coronoid process, condyle (condylar process), pterygoid fovea, neck, lingula, mandibular foramen, mylohyoid line, and mental spines.

Step 2. On the right side, reflect the masseter and zygomatic arch downward toward the angle of the mandible. (Play movie)

Plate N25, TG7-31 shows the partotid gland. You will need to cut through the inferior border of it and reflect it upwards by detaching it from the masseter muscle. The incision should be parallel to the posterior ramus of the mandible. Cut branches of the facial nerve and the cut retromandibular vein (N70, TG7-73) will be visible within the gland when it is reflected. Skin the area overlying the temporalis muscle (N54, TG7-31) and clean the muscle. Plates N24, TG7-36, TG7-75, N46 , TG7-84 show the auriculotemporal nerve (V3), which you will find running with the superficial temporal artery and vein (N23, TG7-35, TG7-71, TG7-73) over the temporalis muscle. Plate N46, TG7-34 identifies the deep temporal nerves. The buccal nerve (V3) can be seen in plate N46, TG7-34. Clean the masseter muscle (plate N54, TG7-31). Plate N46, TG7-34 shows the zygomatic arch removed. You will need to do this by sawing through the arch near the articular eminence and as far forward as possible on the zygomatic bone. Since the masseter attaches to the zygomatic arch (N54, TG7-31) you can now reflect the masseter and arch downward together towards the angle of the mandible. The masseteric nerve (identified in plate N46, TG7-34) will be cut as you reflect the masseter. Next, saw or clip the coronoid process of the mandible (N15, TG7-32B, TG7-32C). The temporalis muscle attaches to this process so now you can reflect the process and temporalis muscle upwards. Be careful not to cut the buccal nerve - it passes through some of the deeper temporalis fibers which insert down along the anterior edge of the mandibular ramus. Plates N46, TG7-34, N69 , TG7-36 show the deep temporal nerves and arteries going to the temporalis muscle.

Step 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)

Saw or clip through the base of the condylar process of the mandible (N15, TG7-32B, TG7-32C). Plate N15 or TG7-32C identifies the mandibular foramen, which will have the inferior alveolar neurovascular structures entering it. Plate N46, TG7-34, TG7-37 shows the inferior alveolar nerve passing down the inside of the mandible to enter the mandibular foramen. Use bone clippers to remove as much of the mandible as possible without removing the mandibular foramen or damaging the inferior alveolar nerve. Plate N55, TG7-34 shows about how much of the mandible you will be able to remove (except the posterior half will be removed, not just the anterior portion).

Step 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)

Plate N55, TG7-34 shows the lateral pterygoid muscle, which you will need to clean. Next, try to find the maxillary artery (TG7-35 - it may be deep to the lateral pterygoid muscle) and try to trace it.

Examine the temporomandibular joint (TMJ) by cutting through its joint capsule (N16, TG7-37). The articular disk and joint capsule are labeled in plate N16. The articular tubercle or eminence is anterior to the mandibular fossa (N4, TG7-06 , N16, TG7-32). Plate N55, TG7-34 shows the lateral pterygoid muscle attaching to the articular disk and pterygoid fovea (shown in plate N15, TG7-32) of the mandible. Now remove the mandibular condyle (N15, TG7-32B, TG7-32C) with its attached disk from the mandibular fossa (N4, TG7-06) and reflect it medially with the lateral pterygoid muscle. Now trace the branches of the maxillary artery: middle meningeal, inferior alveolar, buccal, and muscular branches to masseter, temporalis, medial, and lateral pterygoid muscles (N69, TG7-35). Plate N70, TG7-73 shows the pterygoid plexus of veins and the maxillary vein. Plates N46, TG7-34, N53 (bottom) identify the lingual and inferior alveolar nerves, which can be traced back to the foramen ovale (N46, TG7-36). Plate N46, TG7-36 also identifies the auriculotemporal nerve, chorda tympani nerve joining the lingual nerve and other branches of the mandibular division of the trigeminal nerve (V3). Plate N46, TG7-84 shows the location of the otic ganglion. Plates N125, TG7-90, N133 trace fibers from the glossopharyngeal nerve (IX) to the otic ganglion and eventually to the parotid gland. Plate N55, TG7-34 shows the medial pterygoid muscle.

Step 5. Clear the deep cervical fascia and expose the submandibular gland, the digastric, and mylohyoid muscles and facial artery. (Play movie)

The submandibular triangle is bounded by the anterior and posterior bellies of the digastric muscle and the mandible. Clear the superficial fascia from this triangle. Expose the submandibular gland (N46, TG7-37, N53, N61, and N69, TG7-31). Also, identify the digastric muscle (N27, TG7-17, N28, TG7-12), mylohyoid muscle (plates N27, TG7-34, N28, TG7-12, N53, and N59, TG7-37) and the stylohyoid muscle (plates N46, TG7-17, N59, TG7-40). Plates N69, TG7-18, N70 shows the facial artery and vein running together near the submandibular gland. Plate N46, TG7-37 shows the mylohyoid nerve arising from the inferior alveolar nerve to innervate the mylohyoid muscle and anterior belly of the digastric muscle. Plate N46, TG7-37 shows the submandibular gland and its deep part hooking around the posterior border of the mylohyoid muscle. Plate N46, TG7-37 shows the attachment of the digastric muscle and stylohyoid muscle which both need to be cut from the hyoid bone and reflected laterally. Plate N42, TG7-37 also identifies the hypoglossal nerve (XII), which can be seen passing deep to the mylohyoid muscle in plate N67, TG7-19. Now sever the attachment of the mylohyoid muscle to the mandible and reflect it downward (plate N24, TG7-37). Be careful when reflecting the mylohyoid not to go too deep because there are other muscles deep to this muscle. Plates N53 and N59, TG7-40 identify the hyoglossus muscle. Plate N69, TG7-35 shows the lingual artery branching off from the external carotid artery and plate N63, TG7-40 (bottom) shows the lingual artery supplying the tongue.

Step 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)

Plate N51, TG7-38 shows you roughly the area where you need to make a cut beside the tongue. Plates N51 , TG7-38, N58 (top) identify the palatoglossal fold (arch). Cut the mucosa beside the tongue and reflect the contents laterally toward the mandible to expose the contents of the paralingual space (plate N51, TG7-37, TG7-38).

Step 7. Examine the sublingual gland, the lingual and hypoglossal nerves, the submandibular ganglion and submandibular duct. (Play movie)

This step involves identifying the contents of the paralingual space. Try to find each structure from the inside of the mouth and from the outside of the mouth by digging through the submandibular triangle. Plates N51 , TG7-37A, N61, TG7-37B show the sublingual gland and the submandibular duct. Plates N46, TG7-84, N59, TG7-88, and N61 identify the course of the lingual nerve and show the submandibular ganglion. Plates N53 (bottom) and N61, TG7-37 show the submandibular duct extending from the deep portion of the submandibular gland. Plates N59, TG7-38, N69, TG7-37, and N126 show the hypoglossal nerve, which is the most inferiorly located element within the hypoglossal space.

Step 8. Examine the tongue, identifying its parts, intrinsic and extrinsic muscles. (Play movie)

Plate N58 , TG7-39 features the tongue and labels the foramen cecum, vallate papillae, and the lingual tonsil (N63). The genioglossus, hyoglossus, and styloglossus muscles (extrinsic tongue muscles) are identified in plates N53, N59, TG7-40, N63 and N68, TG7-20. Plate N62, TG7-39 shows the sensory (special and general) innervation of the tongue. The motor innervation of the tongue (all extrinsic and intrinsic muscles) is supplied by the hypoglossal nerve (see plate N126, TG7-94). Plate N126, TG7-38 also identifies the intrinsic muscles of the tongue. Plate N63, TG7-40 identifies the geniohyoid muscle lying between the mylohyoid and genioglossus muscles. Plates N63, TG7-38, N53 (bottom) also show the geniohyoid muscle.

Plate N57 labels the gingiva (gums). Plates N56 and N57 identify central incisors, lateral incisors, canines, (first and second) premolars, and (first, second, and third) molars. Looking at plate N63, TG7-32, the vestibule of the oral cavity can be seen as the space between the lips or cheek and the teeth (TG7-38). The oral cavity itself extends from the lips back to the oropharynx.