Prelab Images - Infratemporal Fossa & Oral Cavity

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 Atlas images listed below.
1. Review the osteology of the infratemporal fossa and oral cavity. (Play movie)
Plates 12 and 14 show the articular eminence, but do not label it (it is the anterior part of the mandibular fossa). Plates 4 and 12 show the mandibular fossa. Plates 6 and 8 identify the medial and lateral pterygoid plates. Plate 4 labels the pterygomaxillary fissure. The foramen ovale can be seen in plates 4, 8, and 11. The foramen spinosum can be seen in plates 8 and 11. Plates 4 and 13 show the styloid process. Plate 13 shows 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 25 (top) 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 (70) will be visible within the gland when it is reflected. Skin the area overlying the temporalis muscle (54) and clean the muscle. Plates 24 and 46 show the auriculotemporal nerve (V₃), which you will find running with the superificial temporal artery and vein (23) over the temporalis muscle. Plate 46 identifies the temporal nerve. The buccal nerve (V₃) can be seen in plate 46. Clean the masseter muscle (plate 54). Plate 46 (top) 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 (54) you can now reflect the masseter and arch downward together towards the angle of the mandible. The masseteric nerve (identified in plate 46) will be cut as you reflect the masseter. Next, saw or clip the coronoid process of the mandible (15). The temporalis muscle attaches to this process so now you can reflect the process and temporalis muscle upwards. Plates 46 and 69 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 (15). Plate 15 identifies the mandibular foramen, which will have the inferior alveolar neurovascular structures entering it. Plate 46 (bottom) 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 55 (top) 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 55 shows the lateral pterygoid muscle, which you will need to clean. Next, try to find the maxillary artery (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 (16). The articular disk and joint capsule are labeled in plate 16. The articular eminence is the part of the temporal bone that contains the mandibular fossa (4, 16). Plate 55 shows the lateral pterygoid muscle attaching to the articular disk and pterygoid fovea (shown in plate 15) of the mandible. Now remove the mandibular condyle (15) with its attached disk from the mandibular fossa (4) 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 (69). Plate 70 shows the pterygoid plexus of veins and the maxillary vein. Plates 46 and 53 (bottom) identify the lingual and inferior alveolar nerves, which can be traced back to the foramen ovale (46). Plate 46 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 46 shows the location of the otic ganglion. Plates 125 and 133 trace fibers from the glossopharyngeal nerve (IX) to the otic ganglion and eventually to the parotid gland. Plate 55 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 (46, 53, 61, and 69). Also, identify the digastric muscle (27 and 28), mylohyoid muscle (plates 27, 28, 53, and 59) and the stylohyoid muscle (plates 46 and 59). Plates 69 and 70 shows the facial artery and vein running together near the submandibular gland. Plate 46 shows the mylohyoid nerve arising from the inferior alveolar nerve to innervate the mylohyoid muscle and anterior belly of the digastric muscle. Plate 46 (top) shows the submandibular gland and its deep part hooking around the posterior border of the mylohyoid muscle. Plate 46 (top) shows the attachment of the digastric muscle and stylohyoid muscle which both need to be cut from the hyoid bone and reflected laterally. Plate 42 (top) also identifies the hypoglossal nerve (XII), which can be seen passing deep to the mylohyoid muscle in plate 67. Now sever the attachment of the mylohyoid muscle to the mandible and reflect it downward (plate 24). Be careful when reflecting the mylohyoid not to go too deep because there are other muscles deep to this muscle. Plates 53 and 59 identify the hyoglossus muscle. Plate 69 shows the lingual artery branching off from the external carotid artery and plate 63 (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 51 (right picture) shows you roughly the area where you need to make a cut under the tongue. Plates 51 (top) and 58 (top) identify the palatoglossal fold (arch). Reflect the contents on either side of the cut you made to expose the contents of the paralingual space (plate 51, right picture).
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 51 and 61 show the sublingual gland and the submandibular duct. Plates 46, 59, and 61 identify the course of the lingual nerve and show the submandibular ganglion. Plates 53 (bottom) and 61 show the submandibular duct extending from the deep portion of the submandibular gland. Plates 59, 69, and 126 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 58 features the tongue and labels the foramen cecum, vallate papillae, and the lingual tonsil (63). The genioglossus, hyoglossus, and styloglossus muscles (extrinsic tongue muscles) are identified in plates 53, 59, 63, and 68. Plate 62 (bottom, left) shows the sensory (special and general) sensation of the tongue. The motor innervation of the tongue (all extrinsic and intrinsic muscles) is supplied by the hypoglossal nerve (see plate 126). Plate 126 also identifies the intrinsic muscles of the tongue. Plate 63 identifies the geniohyoid muscle lying between the mylohyoid and genioglossus muscles. Plates 63 and 53 (bottom) also show the geniohyoid muscle.

Plate 57 labels the gingiva (gums). Plates 56 and 57 identify central incisors, lateral incisors, canines, (first and second) premolars, and (first, second, and third) molars. Looking at plate 63, the vestibule of the oral cavity can be seen as the space between the lips and the teeth. The oral cavity itself extends from the lips back to the oropharynx.