Parotid Salivary gland It is the largest of all salivary glands. Shape: Irregular pyramid in shape. Position: It lies below the external acoustic meatus. It wedges between the ramus of the mandible and sternomastoid muscle. It extends upwards till the level of zygomatic arch and down to the angle of the mandible.

The gland partially overlaps the masseter muscle. A small semi-detached part of the gland lies between the zygomatic arch and the parotid duct which is called: accessory part of the parotid gland.

The gland has: 2 ends; a superior end (surface), an inferior end which extends to to the level of angle of mandible. 3 surfaces; superficial (lateral), anteromedial and posteromedial. The gland is covered by a capsule derived from deep cervical fascia.

Main structures within the substance of the gland: From superficial to deep, they are: Facial nerve and branches. Retromandibular vein and its two divisions, maxillary vein, superficial temporal vein.. External carotid artery and its two terminal branches.

Facial nerve It is the most superficial structure. It enters the gland through its posteromedial surface. It breaks within the gland into terminal branches that leave it through; upper end, lower end and anteromedial surface. These terminal branches are 5; Temporal, zygomatic, buccal, marginal mandibular and cervical.

Other structures within the gland: Auriculotemporal nerve. Posterior auricular artery. Preauricular lymph nodes.

Parotid duct: The duct is about 5 cm in length. It arises from anterior border of the gland. It runs on the masseter muscle. At the anterior border of masseter it runs medially to pierce the buccinator muscle and mucosa to open in the vestibule of the mouth.

Opening of parotid duct: It opens in the vestibule of the mouth opposite the upper second molar tooth. Surface anatomy: The duct is represented by the middle 1/3 of the line between a point on the lower border of tragus of ear and a point midway between the ala of nose and red margin of the upper lip.

Blood supply: Arterial: External carotid artery and its terminal branches within the gland. Venous: Into the retromandibular vein. Lymph drainage: Into Preauricular (parotid), superficial cervical and deep cervical lymph nodes.

Nerve supply: Sensory supply: From Auriculotemporal nerve. Sympathetic supply: From the plexus around external carotid artery. Parasympathetic supply: Otic ganglion.

Parasympathetic supply: From inferior salivary nucleus in brain stem. To glosspharyneal nerve. To its tympanic branch that breaks into tympanic plexus on the tympanic membrane. The fibres then carried by lesser petrosal nerve to relay in otic ganglion. Postganglionic fibers reach the gland via Auriculotemporal nerve.

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