The parotid glands are the largest of the three paired major salivary glands in the head, and numerous structures pass through them. They lie anterior to and below the lower half of the ear, superficial, posterior, and deep to the ramus of the mandible.

Each gland extends down to the lower border of the mandible and up to the zygomatic arch. Posteriorly the gland cover the anterior part of the sternocleidomastoid muscle and continue anteriorly to halfway across the masseter muscle.

The parotid duct leaves the anterior edge of the parotid gland midway between the zygomatic arch and the corner of the mouth. 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 maxillary molar tooth.

Arterial supply

The parotid gland receives its arterial supply from the numerous arteries that pass through its substance. (See below.)

Innervation

Sensory innervation of the parotid gland is provided by the auriculotemporal nerve (branch of the mandibular nerve (CN 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 (CN IX).

Several major structures enter and pass through or pass just deep to the parotid gland. These include the:

Facial nerve (CN VII)
External carotid artery and its branches
Retromandibular vein and its tributaries

Facial nerve

The facial nerve (CN 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.

External carotid artery and its branches

The external carotid artery enters into or passes deep to the inferior border of the parotid gland. As it continues in a upward direction, it gives off the posterior auricular artery before dividing into its two terminal branches (maxillary artery and superficial temporal artery) 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.

Retromandibular vein and its tributaries

The retromandibular vein is formed in the substance of the parotid gland when the superficial temporal vein and maxillary vein join together, and pass inferiorly in the substance of the parotid gland. This vein usually divides into anterior and posterior branches just below the inferior border of the gland.

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Parotid gland