Salivary glands

Definition

Salivary glands are exocrine glands in the oral cavity that produce and secrete saliva. Saliva contains enzymes (like amylase) that begin the breakdown of carbohydrates, as well as mucus, electrolytes, and antimicrobial agents that maintain oral health.

The salivary system is divided into two main groups: the three pairs of **major salivary glands** and hundreds of **minor salivary glands**.

Major Salivary Glands

1. Parotid Gland

The largest of the salivary glands, located bilaterally in the pre-auricular region (in front of the ears).

Secretory type: Purely serous (watery) secretion.
Duct: Parotid duct (Stensen's duct), which opens into the oral vestibule opposite the maxillary second molar.
Innervation: Secretomotor supply from the Glossopharyngeal nerve (CN IX).
Clinical Note: The facial nerve (CN VII) passes through the gland but does not innervate it.

2. Submandibular Gland

Located in the submandibular triangle, medial to the body of the mandible.

Secretory type: Mixed, but predominantly serous.
Duct: Submandibular duct (Wharton's duct), which opens at the sublingual caruncle at the base of the tongue.
Innervation: Secretomotor supply from the Facial nerve (CN VII) via the chorda tympani.

3. Sublingual Gland

The smallest of the major glands, located in the floor of the mouth, superior to the mylohyoid muscle.

Secretory type: Mixed, but predominantly mucous (thick).
Duct: Multiple small ducts (ducts of Rivinus) and the major sublingual duct (Bartholin's duct).
Innervation: Same as the submandibular gland (CN VII).

Minor Salivary Glands

There are 600 to 1,000 minor salivary glands distributed throughout the oral mucosa (except the anterior hard palate and gingiva). They are primarily mucous-secreting and provide continuous lubrication.

Microscopic Anatomy

The functional unit of a salivary gland is the salivon, which consists of:

Acinus: A cluster of cells that produce the primary secretion.
Intercalated duct: Short duct leading from the acinus.
Striated duct: Involved in the reabsorption of sodium and secretion of potassium, making saliva hypotonic.
Excretory duct: The final path to the oral cavity.

Clinical Significance

Sialolithiasis: The formation of "salivary stones," most common in Wharton's duct due to the upward flow and high calcium content of submandibular saliva.
Xerostomia: The subjective feeling of dry mouth, often a side effect of medications or Sjogren's syndrome.
Mucocele: A common lesion caused by the rupture of a minor salivary gland duct, leading to mucus extravasation into the tissue.
Pleomorphic Adenoma: The most common benign tumor of the salivary glands, usually occurring in the parotid.