Salivary glands play a critical role in oral health, digestion, and protection of the teeth and oral tissues. These glands are responsible for producing saliva, an essential fluid that aids in chewing, swallowing, digestion, lubrication of oral tissues, and antimicrobial defense. Disorders of the salivary glands are common reasons for referral to an oral and maxillofacial surgeon and can significantly affect quality of life.
Understanding the anatomy and function of the salivary glands is essential for diagnosing conditions such as salivary gland stones, infections, cysts, and tumors.
What Are Salivary Glands?
Salivary glands are exocrine glands, meaning they secrete their products through a system of ducts rather than directly into the bloodstream. Saliva is delivered into the oral cavity through these ducts, where it performs multiple protective and digestive functions.
Humans have three paired major salivary glands—the parotid, submandibular, and sublingual glands—as well as hundreds of minor salivary glands distributed throughout the oral mucosa. These glands can be classified based on the type of saliva they produce: serous, mucous, or seromucous (mixed).
Parotid Gland
The parotid gland is the largest of the major salivary glands and is located in front of and slightly below the ear. It produces a purely serous secretion, which is rich in enzymes, particularly amylase. Amylase plays a key role in the digestion of starches, beginning the digestive process in the mouth.
Saliva from the parotid gland enters the oral cavity through Stensen’s duct, which opens opposite the maxillary second molar. Because of its location and duct anatomy, the parotid gland is more commonly affected by inflammatory conditions and tumors than by salivary stones.
Submandibular Gland
The submandibular gland is located beneath the mandible in the submandibular triangle and is responsible for producing approximately 65–70% of total saliva in the mouth. This gland secretes a mixed serous and mucous saliva, providing both enzymatic activity and lubrication.
Saliva from the submandibular gland drains into the oral cavity through Wharton’s duct, which opens at the sublingual caruncle near the base of the tongue. Due to the tortuous course of Wharton’s duct, its uphill flow, and the thicker, more mucous-rich saliva it produces, the submandibular gland is the most common salivary gland to develop salivary stones (sialoliths).
Salivary stones in this gland can cause pain and swelling, particularly during meals, and are a frequent indication for oral surgery consultation.
Sublingual Gland
The sublingual gland is the smallest of the three major salivary glands and is located beneath the mucosa of the floor of the mouth. It produces saliva that is predominantly mucous in nature, contributing mainly to lubrication rather than enzymatic digestion.
The sublingual gland accounts for approximately 5% of total saliva production. Unlike the parotid and submandibular glands, it does not rely on a single major duct. Instead, saliva exits the gland directly into the oral cavity through 8 to 20 small excretory ducts known as the ducts of Rivinus.
Because of its multiple small ducts and mucous secretions, the sublingual gland is less commonly affected by salivary stones but may be involved in conditions such as ranulas or mucous retention cysts.
Minor Salivary Glands
In addition to the major salivary glands, the oral cavity contains hundreds of minor salivary glands located in the lips, cheeks, palate, tongue, and pharynx. These glands primarily produce mucous saliva and help maintain constant moisture of the oral tissues. While small, they are clinically significant, particularly because many salivary gland tumors arise from minor salivary glands.
Clinical Importance of Salivary Gland Anatomy
A thorough understanding of salivary gland anatomy is essential for diagnosing and treating conditions such as salivary stones, infections (sialadenitis), cysts, autoimmune disorders like Sjögren’s syndrome, and salivary gland tumors. Imaging studies, clinical examination, and sometimes surgical intervention are required to manage these conditions effectively.
Conclusion
Salivary glands are vital structures that support digestion, oral health, and tissue protection. The parotid, submandibular, and sublingual glands each play unique roles in saliva production and differ in anatomy, secretion type, and susceptibility to disease. Knowledge of their function and ductal anatomy is essential for accurate diagnosis and effective treatment of salivary gland disorders.
Patients experiencing persistent dry mouth, swelling, pain during meals, or recurrent infections should seek evaluation by an oral and maxillofacial surgeon to determine the underlying cause and appropriate management.
