Parotid Glands

Overview

The parotid glands are the largest of the three paired major salivary glands in the human body. As exocrine glands, their primary role is the production and secretion of saliva into the oral cavity, particularly serous (watery, enzyme-rich) saliva. These glands play a vital role in initiating digestion, maintaining oral health, and facilitating speech and swallowing.

Location

Each parotid gland is located in the preauricular region (in front of and slightly below the ear). Specifically, it:

• Occupies the space between the mandible and the sternocleidomastoid muscle

• Extends from the zygomatic arch (cheekbone) superiorly to the angle of the mandible inferiorly

• Is traversed by the facial nerve (CN VII) as it branches within the gland

Saliva from the parotid gland is secreted into the mouth through the parotid duct (Stensen’s duct), which opens near the second upper molar tooth.

Structure

Each parotid gland has the following key structural features:

• Capsule: Enclosed in a tough fibrous capsule derived from the deep cervical fascia (parotid sheath)

• Lobular parenchyma: Composed mainly of serous acini, which produce watery, enzyme-rich saliva

• Stensen’s duct: A straight excretory duct approximately 5 cm long, opening into the oral vestibule

• Facial nerve branches: Divide the gland into superficial and deep lobes but do not innervate the gland

• Arterial supply: Primarily from branches of the external carotid artery (e.g., superficial temporal and maxillary arteries)

• Venous drainage: Into the retromandibular vein

• Innervation: Parasympathetic innervation via the glossopharyngeal nerve (CN IX) through the otic ganglion and auriculotemporal nerve

Function

The main functions of the parotid glands are:

• Saliva production: Produces approximately 25% of total daily saliva, especially during chewing and eating

• Secretion of digestive enzymes: Especially salivary amylase (ptyalin), which begins starch digestion in the mouth

• Lubrication: Moistens food for easier mastication and swallowing

Physiological Role(s)

The parotid glands contribute to multiple physiological processes:

• Digestion: Initiate carbohydrate breakdown via amylase

• Oral hygiene: Saliva helps cleanse the mouth and buffer oral pH, inhibiting bacterial growth

• Taste facilitation: Saliva acts as a solvent for taste molecules, enhancing taste perception

• Speech: Moistens oral structures, aiding articulation and phonation

Clinical Significance

The parotid glands are involved in several important medical conditions:

• Parotitis: Inflammation of the parotid gland, commonly due to viral infection such as mumps; characterized by painful swelling near the ear

• Sialolithiasis: Stone formation in the parotid duct can obstruct saliva flow, causing swelling and pain, especially while eating

• Parotid tumors: Can be benign (e.g., pleomorphic adenoma) or