Dissector Answers - 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.
2. Identify three main neurovascular structures that traverse the gland: the facial nerve, the retromandibular vein and external carotid artery.
3. Identify the branches of the facial nerve in the face.
4. Identify some exemplary muscles of facial expression acting on the oral opening.
5. Trace the course of the facial artery and facial vein in the face.

Learning Objectives and Explanations:

1. Describe the location of the parotid salivary gland posterior and deep to the ramus of the mandible, within the parotid fossa (N4, N25, TG7-30A, TG7-30B, TG7-31A)

The parotid gland extends into the parotid fossa, anteroinferior to the external acoustic meatus, wedged between the ramus of the mandible and the mastoid process. The apex of the parotid gland is posterior to the angle of the mandible, and its base is related to the zygomatic arch.

2. Identify three main neuromuscular structures that traverse the gland: the facial nerve, the retromandibular vein and external carotid artery. (N25, N69, N70, TG7-19, TG7-31)

From superficial to deep, the structures traversing the gland are arranged: facial nerve and its branches, retromandibular vein, and external carotid artery. Retromandibular vein is formed by the union of the superficial temporal and maxillary veins. It divides into anterior and posterior divisions and drains the sides of the head, scalp, and deep face.

3. Identify the branches of the facial nerve in the face. (N25, N123, TG7-87)

Branches of the facial nerve include: temporal, zygomatic, buccal, marginal mandibular and cervical. The temporal branch of the facial nerve emerges from the superior border of the parotid gland and crosses the zygomatic arch. The zygomatic branches pass via two or three branches to the eye to innervate the inferior part of the orbicularis oculi and other facial muscles inferior to the orbit. Buccal branches pass external to the buccinator to innervate this muscle and muscles of the upper lip. The (marginal) mandibular branch innervates the muscles of the lower lip and chin. It emerges from the inferior border of the parotid gland and crosses the inferior border of the mandible deep to the platysma to reach the face. The cervical branch passes from the inferior border of the parotid gland to the mandible to innervate the platysma.

4. Identify some exemplary muscles of facial expression acting on the oral opening. (N26, N54, N69, N123, TG7-29, TG7-30, TG7-31, TG7-87)

Zygomaticus major, levator labii superioris, depressor labii inferioris, levator anguli oris, depressor anguli oris, and orbicularis oris, and buccinator are all innervated by the facial nerve (CN VII) and supplied by the facial artery. Zygomaticus major arises from the upper lateral surface of the zygomatic bone to insert into the skin of the upper lip. It elevates and draws the corner of mouth laterally. Levator labii superioris originates from the inferior margin of the orbit to insert on the skin of upper lip. It elevates the upper lip. Levator anguli oris attaches superiorly to the infraorbital margin and inferiorly to the angle of the mouth. Depressor anguli oris depresses the angle of the mouth. Posterior fibers of the platysma assist with this movement. Depressor labii inferioris, lateral to the mentalis, attaches inferiorly to the mandible and merges superiorly with its contralateral partner and the orbicularis oris and draws the lip inferiorly and slightly laterally. Orbicularis oris originates from the skin and fascia of the lips and inserts in the skin and fascia of the lips. It purses the lips. The buccinator runs from the mandible to the angle of the mouth and lateral portion of the lips. It pulls the corner of the mouth laterally. It is important to note that although this muscle lies fairly deeply in the face, it is still innervated by the facial nerve, not the trigeminal nerve (which penetrates buccinator with branches of the buccal NERVE, a sensory nerve, as opposed to buccal BRANCHES of facial nerve, that are motor).

5. Trace the course of the facial artery and facial vein in the face. (N16, N69, N70, TG7-19, TG7-31)

Facial artery: arising from the external carotid, it winds to the inferior border of the mandible deep to the platysma. It crosses the mandible, buccinator, and maxilla as it courses over the face to the medial angle of the eye. The facial artery lies deep to the zygomaticus major and levator labii superioris muscles. It eventually anastomoses with the ophthalmic artery.

Facial vein: begins near the medial angle of the eye and the inferior border of the orbit as the continuation of the angular vein. The facial vein runs inferolaterally through the face, posterior to the facial artery.