Salivary glands are specialized organs located within and around the mouth, producing saliva. This fluid plays a significant role in maintaining overall oral health and initiating the digestive process. The glands moisten the mouth, which is beneficial for speech and comfortable swallowing. The human body can produce 0.5 to 1.5 liters of saliva daily.
The Major Salivary Glands
Three pairs of major salivary glands produce the majority of saliva. These glands are larger and have specific ducts that transport saliva into the oral cavity.
Parotid Glands
The parotid glands, the largest of the major salivary glands, are positioned on either side of the face, in front of the ears and extending over the jawbone. Each parotid gland secretes serous saliva, which contains the enzyme amylase. This secretion is delivered into the mouth through Stensen’s duct, which opens near the upper second molar on the inside of the cheek.
Submandibular Glands
Located beneath the floor of the mouth, along the inner side of the lower jaw, are the submandibular glands. These are the second largest major glands, typically about the size of a walnut. They produce a mixed type of saliva, containing both serous and mucous components, though serous secretion often predominates. Saliva from these glands enters the oral cavity via Wharton’s duct, which opens under the tongue near the lingual frenulum.
Sublingual Glands
The sublingual glands are the smallest of the major salivary glands, resembling an almond in size and shape. They are situated directly under the tongue, anterior to the submandibular glands. These glands primarily secrete thick, viscous mucous saliva, with some serous elements. Unlike the other major glands, the sublingual glands release saliva through numerous small ducts, known as the ducts of Rivinus, directly onto the floor of the mouth beneath the tongue.
The Minor Salivary Glands
The oral cavity contains hundreds of smaller minor salivary glands. These glands are scattered throughout the lining of the mouth, including the lips, cheeks, palate, and tongue. They are typically 1 to 2 millimeters in diameter, and unlike the major glands, are not surrounded by a connective tissue capsule.
These glands produce a continuous, low volume of saliva, predominantly mucous in nature. Their primary function is to provide constant lubrication and moisture to the oral mucosa. This steady secretion helps keep the mouth moist and contributes to the health of the oral tissues, independent of meal-related stimulation.
Saliva Composition and Function
Saliva is a complex fluid, composed of over 99% water. The remaining portion consists of various dissolved substances, including electrolytes like sodium, potassium, calcium, and bicarbonate. Saliva also contains enzymes such as salivary amylase, which begins the breakdown of starches, and lingual lipase, which starts fat digestion.
This fluid also includes mucus, which provides lubrication, and antimicrobial agents like lysozyme and secretory IgA, offering a defense against bacteria and viruses. Saliva moistens food for easier chewing and swallowing, and aids in speech. It helps maintain oral hygiene by washing away food debris and neutralizing acids produced by bacteria, thereby protecting tooth enamel from decay. Saliva also contributes to the remineralization of teeth, helping to repair microscopic damage to the enamel surface.