Prelab Images - Parotid Gland & Face

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 relevant osteology of the skull and mandible. (Play movie)

Plate N4, TG7-04A labels the zygomatic arch, external acoustic meatus, mastoid process, and styloid process. The stylomastoid foramen is labeled in plate N8, TG7-06 and the facial nerve can be seen exiting the cranial base from this foramen in plate N123, TG7-87. Plate N15, TG7-32B, TG7-32C labels the ramus, angle, body, and mental foramen of the mandible. The posterior border of the mandible is not labeled, but the term is self-explanatory. The symphysis of the mandible can be seen in plate N2, TG7-03. The rim of the orbit, supraorbital notch, and infraorbital foramen are shown in plate N2, TG7-03, TG7-57.

Step 2. Remove the skin of the face except for eyelids and nose. (Play movie)

Skin the face from the inferior border of the mandible to above the zygomatic arch and as far laterally as the mastoid process on both sides. Trace the greater auricular nerve (N24, TG7-36, TG7-75, N31, TG7-13, N32, TG7-15). This nerve comes from the cervical plexus and was identified in an earlier lab on the neck.

Step 3. Expose the parotid gland and its duct, carefully dissecting the branches of the facial nerve passing through it. (Play movie)

Plate N25 shows the parotid gland. In the lab the gland will be covered by fat and parotid fascia. Remove the parotid fascia and fat to clearly see the gland. Use a probe and blunt dissection to identify the neurovascular structures for the remainder of step 2. The auriculotemporal nerve can be seen in plates N24, TG7-36, TG7-75, N46, TG7-84, N122, TG7-81. This nerve is a branch of the mandibular division of the trigeminal nerve (CN V3). One of its functions is to carry parasympathetic fibers from the glossopharyngeal nerve (CN IX) to the parotid gland (see plate N125, TG7-89 for CN IX sending some fibers to V3). The superficial temporal artery and vein can be seen in plates N23, TG7-35, TG7-71, TG7-72, and TG7-73, N69, TG7-19, N70. The parotid duct is labeled in plates N23, TG7-35, TG7-71, TG7-72, and TG7-73, N25, TG7-31, N51 (bottom) or TG7-38, N54, TG7-31. Note that the parotid duct pierces the buccinator muscle to enter the oral cavity near the upper molars. Plates N25, TG7-31 and N123, TG7-87 identify the temporal, zygomatic, buccal, (marginal) mandibular, and cervical branches of the facial nerve, which will go to innervate the muscles of facial expression.

Step 4. Identify the branches of the facial nerve within the parotid gland. (Play movie)

Plates N25, TG7-31 and N123, TG7-87 identify the temporal, zygomatic, buccal, (marginal) mandibular, and cervical branches of the facial nerve, which will go to innervate the muscles of facial expression. Using blunt dissection, dig under the parotid gland so you can locate the stylomastoid process behind the gland (see plates N13, TG7-09 and N25, TG7-31 for the relationship of the stylomastoid process to the parotid gland). Plates N27 or TG7-16 and N28, TG7-12 identify the posterior belly of the digastric muscle and the stylohyoid muscle. You should be able to identify these muscles deep to the parotid gland.

Step 5. Identify the retromandibular vein and its divisions and review the branches of the external carotid artery to the face region. (Play movie)

Plate N70 shows the formation of the retromandibular vein from the union of the superficial temporal (N23, TG7-35, TG7-71, TG7-72, and TG7-73) and maxillary veins. The retromandibular vein divides into anterior and posterior divisions. Plate N70 shows the anterior division uniting with the facial vein to form the common facial vein (which then drains into the internal jugular vein). Plate N70 also shows the posterior division of the retromandibular vein uniting with the posterior auricular vein to form the external jugular vein. Plates N61, TG7-31, N69, TG7-19, N71, TG7-20 show the relation of the external carotid artery to the parotid gland within the parotid fossa. Plate N69, TG7-19 identifies the branches of the external carotid artery (superior thyroid, ascending pharyngeal, lingual, facial, occipital, superficial temporal, and maxillary). Identify and trace all of these branches, except for the maxillary artery, which will be identified in a later lab.

Step 6. Clean and identify the muscles of facial expression related to the mouth. (Play movie)

Plate N123, TG7-87 features the facial nerve and shows it innervating the muscles of facial expression. Plate N26, TG7-30 shows the following muscles of facial expression: zygomaticus major, levator labii superioris, depressor anguli oris, depressor labii inferioris, and orbicularis oris. These muscles are also labeled in plate N54, TG7-31. In addition, plate N54, TG7-31 labels the levator anguli oris (partially obscured by the zygomaticus major muscle). Plates N26, TG7-30 and N54, TG7-31 show the buccinator muscle. This muscle is a little deeper than the above muscles. A buccal fat pad exists between the masseter muscle (see plate N54, TG7-31) and the buccinator muscle. If you look closely at plate N23, TG7-35, TG7-71, TG7-72, and TG7-73 you can see a tiny bit of this fat pad sticking out from underneath the masseter muscle. Plate N23, TG7-35, TG7-71, TG7-72, and TG7-73, N70, and N69, TG7-19 trace the facial vein and artery, which you will need to do during the lab.

Step 7. Expose the supraorbital, infraorbital and mental branches of CN V. (Play movie)

Plate N122, TG7-81 shows an overview of the trigeminal nerve (CN V). Plate N24, TG7-36, TG7-75 not only shows all the sensory branches of the trigeminal nerve, but it also shows sensory branches from the cervical plexus and dorsal primary rami to provide an overview of the cutaneous nerves of the head and neck. The supraorbital nerve (from ophthalmic nerve, V1), infraorbital nerve (from maxillary nerve, V2), and the mental nerve (from mandibular nerve, V3) are identified in plates N122, TG7-81, N24, TG7-36, TG7-75, N36, TG7-30, N45, TG7-81, TG7-82, and TG7-83 and N46, TG7-84.