The parotid duct leaves the anterior edge of the parotid gland midway between the zygomatic arch and the corner of the mouth (Fig. 8.62). It crosses the face in a transverse direction and, after crossing the medial border of the masseter muscle, turns deeply into the buccal fat pad and pierces the buccinator muscle. It opens into the oral cavity near the second upper molar tooth.
pass just deep to the parotid gland. These include the facial nerve [VII], the external carotid artery and its branches, and the retromandibular vein and its tributaries (Fig. 8.62).
The facial nerve [VII] exits the skull through the stylomastoid foramen and then passes into the parotid gland, where it usually divides into upper and lower trunks. These pass through the substance of the parotid gland, where there may be further branching and anastomosing of the nerves.
Five terminal groups of branches of the facial nerve [VII]—the temporal, zygomatic, buccal, marginal mandibular, and cervical branches—emerge from the upper, anterior, and lower borders of the parotid gland (Fig. 8.62).
The intimate relationships between the facial nerve [VII] and the parotid gland mean that surgical removal of the parotid gland is a difficult dissection if all branches of the facial nerve [VII] are to be spared.
The external carotid artery enters into or passes deep to the inferior border of the parotid gland (Fig. 8.62). As it continues in a superior direction, it gives off the posterior auricular artery before dividing into its two terminal branches (the maxillary and superficial temporal arteries) near the lower border of the ear:
The maxillary artery passes horizontally, deep to the mandible.
The superficial temporal artery continues in a superior direction and emerges from the upper border of the gland after giving off the transverse facial artery.
The retromandibular vein is formed in the substance of the parotid gland when the superficial temporal and maxillary veins join together (Fig. 8.62), and passes inferiorly in the substance of the parotid gland. It usually divides into anterior and posterior branches just below the inferior border of the gland.
The parotid gland receives its arterial supply from the numerous arteries that pass through its substance.
Sensory innervation of the parotid gland is provided by the auriculotemporal nerve, which is a branch of the mandibular nerve [V3]. This division of the trigeminal nerve exits the skull through the foramen ovale.
The auriculotemporal nerve also carries secretomotor fibers to the parotid gland. These postganglionic parasympathetic fibers have their origin in the otic ganglion associated with the mandibular nerve [V3] and are just inferior to the foramen ovale. Preganglionic parasympathetic fibers to the otic ganglion come from the glossopharyngeal nerve [IX].
During development a cranial nerve becomes associated with each of the pharyngeal arches. Because the face is primarily derived from the first and second pharyngeal arches, innervation of neighboring facial structures is as follows:
The trigeminal nerve [V] innervates facial structures derived from the first arch.
The facial nerve [VII] innervates facial structures derived from the second arch.
Because the face is derived developmentally from a number of structures originating from the first pharyngeal arch, cutaneous innervation of the face is by branches of the trigeminal nerve [V].