Boundaries of the Parotid Gland

Study Notes

The anterior border separates the superficial surface from the anteromedial surface, extending from the anterior part of the superior surface to the apex.
The parotid duct, most of the terminal branches of the facial nerve, and the transverse facial vessels emerge at this border.
The accessory parotid gland lies on the parotid duct close to this border.
The posterior border separates the superficial surface from the posteromedial surface, overlapping the sternocleidomastoid.
The medial edge or pharyngeal border separates the anteromedial surface from the posteromedial surface, relating to the lateral wall of the pharynx.

Arteries: The external carotid artery enters the gland through its posteromedial surface, while the maxillary artery leaves the gland through its anteromedial surface.
The superficial temporal artery gives the transverse facial artery and emerges at the anterior part of the superior surface.
Veins: The retromandibular vein is formed within the gland by the union of the superficial temporal and maxillary veins.
The retromandibular vein divides into anterior and posterior divisions in the lower part of the gland, emerging close to the apex.
Facial Nerve:
- Leaves the skull by passing through the stylomastoid foramen.
- Crosses the lateral side of the base of the styloid process.
- Enters the posteromedial surface of the parotid gland, runs forwards through the gland, crossing the retromandibular vein and the external carotid artery.
- Divides into two branches (temporofacial and cervicofacial) behind the neck of the mandible.
- Temporofacial branch gives temporal and zygomatic branches, while cervicofacial branch gives buccal, marginal mandibular, and cervical branches.
- These five terminal branches emerge along the anterior border and apex of the parotid gland.

Communicating branches with adjacent cranial and spinal nerves.
Posterior auricular nerve:
- Arises just below the stylomastoid foramen.
- Supplies auricularis posterior, occipitalis, and intrinsic muscles on the back of auricle.
Digastric branch:
- Arises close to the posterior auricular nerve.
- Supplies the posterior belly of the digastric.
Stylohyoid branch:
- Arises with the digastric branch.
- Supplies the stylohyoid muscle.
Terminal branches:
- Temporal branches supply auricularis anterior, auricularis superior, intrinsic muscles on the lateral side of the ear, frontalis, orbicularis oculi, and corrugator supercilii.
- Zygomatic branches supply the orbicularis oculi.
- Buccal branches supply muscles in that vicinity, especially the buccinator.
- Marginal mandibular branch supplies muscles of the lower lip and chin.
- Cervical branch supplies the platysma.

Bell's palsy: Sudden paralysis of facial nerve at the stylomastoid foramen, resulting in asymmetry of the corner of the mouth, inability to close the eye, disappearance of the nasolabial fold, and loss of wrinkling of the skin of the forehead on the same side.