Overview
Large, irregular and lobulated salivary glands located bilaterally on the side of the face in the pre-auricular region (parotid space). It extends inferiorly from the zygomatic arch to the upper part of the neck. It lies between the ramus of the mandible anteriorly and the mastoid and styloid process of the temporal bone posteriorly.
It is the largest of the salivary glands, producing and secreting predominantly serous saliva into the oral cavity via the parotid duct.
Structure
- Upper Pole – Adheres to cartilage of EAM. Adjacent to capsule of TMJ.
- Lower Pole – Posterior to angle of mandible
- Accessory parotid gland – Lies on masset between main parotid duct and zygomatic arch
Surfaces
- Parotid capsule – an envelope formed by the splitting of the deep cervical fascia.
- Lateral (superficial) surface – Covered by skin and superficial fascia.
- Anteromedial surface – U-shaped, grooved by the mandibular ramus
- Posteromedial surface – Contacts the mastoid process, sternocleidomastoid and posterior belly of digastric.
Relations
- Superiorly: zygomatic arch, temporomandibular joint, external auditory meatus
- Inferiorly: inferior border of the mandible
- Anteriorly: masseter (a muscle of mastication)
- Posteriorly: Posterior belly of digastric, anterior border of sternocleidomastoid, external ear
- Superficially: skin and superficial fascia
Ducts
Parotid duct
- The parotid duct (of Stensen) arises from the anterior surface of the gland, traversing the anterior surface of the masseter and pierces the buccal fat pad and buccinator to open in the oral cavity near the second upper molar.
Accessory parotid duct
- A normal anatomical variant
- The accessory parotid duct usually lies on the masseter between the duct and the zygomatic arch
- Opens into the main parotid duct via several small ducts
Contents
- External carotid artery – bifurcates into two terminal branches; the maxillary artery (larger) and the superficial temporal
- Retromandibular vein – formed by the convergence of the superficial temporal and maxillary vein
- Facial nerve – five terminal branches: temporal, zygomatic, buccal, marginal mandibular, cervical
- Intraparotid lymph nodes
Arterial Supply
- Posterior auricular (branch of external carotid artery)
- Superficial temporal (branch of external carotid artery)
Venous Drainage
- Retromandibular vein – empties into internal jugular vein
Lymphatic Drainage
- There are normally around 20 intraparotid lymph nodes.
- Nodes are present within the parotid because of late encapsulation of the gland (compare with early encapsulation of the submandibular gland, which has no nodes within it).
- Parotid nodes are 1st-order drainage for the external auditory canal, pinna, and surrounding scalp.
- Consequently, skin malignancy in this area such as squamous cell carcinoma or melanoma will manifest nodal metastases within the parotid gland.
- Intraparotid lymph nodes drain to the pre-auricular (parotid) nodes, then to nodes of the upper group of deep cervical nodes
Innervation
- Sensory: Auriculotemporal nerve (branch of the mandibular division of the trigeminal nerve) and great auricular nerve (cutaneous branch of the cervical plexus)
- Sympathetic: Superior cervical ganglion from the sympathethic trunk
- Parasympathetic: Glossopharyngeal nerve, via lesser petrosal nerve and otic ganglion
Development
A groove that appears in the ectoderm of the stomodeum (mouth pit) develops into a tunnel from the blind end of which cells proliferate to form the gland
Anatomical Variants
- Congenital agenesis – unilateral or bilateral
- Accessory parotid gland
- Facial process – anterior extension of glandular tissue along parotid duct
- Ectopic parotid tissue
- Parotid duct duplication
- Variable branching of facial nerve in parotid gland