Lab Manual - Parotid Gland & Face

Learning Objectives:

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

  1. Describe the location of the parotid salivary gland posterior and deep to the ramus of the mandible, within the parotid fossa. (explanation)
  2. Identify three main neurovascular structures that traverse the gland: the facial nerve, the retromandibular vein and external carotid artery. (explanation)
  3. Identify the branches of the facial nerve in the face. (explanation)
  4. Identify some exemplary muscles of facial expression acting on the oral opening. (explanation)
  5. Trace the course of the facial artery and facial vein in the face. (explanation)

Readings and Modules:

Procedure:

1. Review the relevant osteology of the skull and mandible. (Play movie; View images: N 2, 4, 8, 15, 123, TG 7-03, 7-04A, 7-06, 7-32B, 7-32C, 7-57, 7-87)

Locate on the skeleton or palpate: the zygomatic arch (zygoma), external acoustic meatus (bony and cartilaginous), mastoid process, styloid process, stylomastoid foramen, ramus, posterior border, angle, body, mental foramen, and symphysis of mandible; rim of orbit, supraorbital notch or foramen, and infraorbital foramen.

2. Remove the skin of the face except for eyelids and nose. (Play movie; View images: N 24, 31, 32, TG 7-13, 7-15, 7-36, 7-75)

Skin the face from the inferior border of the mandible to several centimeters above the zygomatic arch, and from the mastoid process to the anterior mid-line (exclusive of the eyelids and nose, which will be done later). Trace the great auricular nerve to its distribution to the skin over the angle of the mandible.

3. Expose the parotid gland and its duct, carefully dissecting the branches of the facial nerve passing through it. (Play movie; View images: N 23, 24, 25A, 25B, 46, 51, 54, 69, 70, 122, 123, 125, TG 7-19, 7-31A, 7-31B, 7-35, 7-36, 7-38, 7-71, 7-72, 7-73, 7-75, 7-81, 7-84, 7-87, 7-89)

Remove the subcutaneous fat overlying the parotid gland and expose the deep fascia covering the gland. This is the parotid fascia (parotideo-masseteric). Remove this fascia from the superficial surface of the gland, but do not cut around the borders of the gland with a scalpel. Using a probe, begin at the top of the gland and carefully dissect along its borders for nerves and other structures that emerge from them. Identify: auriculotemporal nerve, superficial temporal artery and vein, parotid duct, and the temporal, zygomatic, buccal, (marginal) mandibular and cervical branches of the facial nerve.

4. Identify the branches of the facial nerve within the parotid gland. (Play movie; View images: N 13, 25, 27, 28, 123, TG 7-09, 7-12, 7-16, 7-31, 7-87)

Follow the branches of the facial nerve into the substance of the parotid gland, carefully removing the gland tissue from around these branches. Trace the facial nerve to the stylomastoid formen, and observe that it passes lateral to the retromandibular vein and external carotid artery. Identify the temporofacial division of the facial nerve, giving temporal, zygomatic, and buccal branches, and the cervicofacial division of the facial nerve with its buccal, (marginal) mandibular, and cervical branches.

5. Identify the retromandibular vein and its divisions and review the branches of the external carotid artery to the face region. (Play movie; View images: N 23, 61, 69A, 69B, 70, 71, TG 7-19, 7-20, 7-31, 7-35, 7-71, 7-72, 7-73)

Next, dissect the parotid gland free from the anterior border of the sternocleidomastoid muscle and palpate the styloid process, which is deep to the gland. Identify the posterior belly of the digastric muscle and the stylohyoid muscle. Find the anterior and posterior divisions of the retromandibiular vein emerging from the gland. The anterior division unites with the facial vein to form the common facial vein, while the posterior division of retromandibular vein unites with the posterior auricular vein to form the external jugular vein. While identifying the stylohyoid muscle, look for the external carotid artery that is curving around the muscle to penetrate into the parotid fossa and gland.

Trace the external carotid artery to its termination and review or find the following branches: superior thyroid, ascending pharyngeal, lingual, facial, occipital, and superficial temporal. The maxillary artery, an important branch of the external carotid, will be seen when the infratemporal fossa is studied.

Angiogram of the head and neck

6. Clean and identify the muscles of facial expression related to the mouth. (Play movie; View images: N 23, 26, 54A, 54B, 69, 70, 123, TG 7-19, 7-30, 7-31, 7-35, 7-71, 7-72, 7-73, 7-87)

The muscles of facial expression are innervated by branches of the facial nerve (CN VII). They lie primarily within the subcutaneous tissue, surround natural orifices (mouth, nose, orbit, ear) and provide a variety of facial expressions. They originate from bone or fascia, but insert into the skin. Review the general arrangement of the muscles in your atlas, but dissect only the following which act on the oral opening: zygomaticus major, levator labii superioris, levator anguli oris, depressor anguli oris, depressor labii inferioris, and orbicularis oris. On one side only, expose the buccinator, which is the deepest of the facial muscles, and main muscle of the cheek. Note the buccal fat pad interposed between the buccinator and the masseter muscle. As the facial muscles are exposed, trace the facial artery and vein past the lips and toward the medial angle of the eye.

Surface anatomy of the face

7. Expose the supraorbital, infraorbital and mental branches of CN V. (Play movie; View images: N 24A, 24B, 36, 45, 46, 122, TG 7-30, 7-36, 7-75, 7-81, 7-82, 7-83, 7-84)

The trigeminal nerve (CN V) provides sensory input from the skin of the face. Identify the following cutaneous branches of the trigeminal: supraorbital (from V1), infraorbital (from V2), and mental (from V3).