The salivary glands are organs responsible for producing and secreting saliva. These exocrine glands release their secretions into a duct that carries the fluid to the surface of the mouth. Saliva production is a continuous process, yielding between 0.5 and 1.5 liters of fluid daily. This fluid is necessary for maintaining oral health and initiating the digestive process.
The Major Salivary Glands
The human body contains three main pairs of salivary glands, which account for the bulk of saliva production. Each pair is distinctly located in the face and neck region and is named based on its anatomical position.
The largest are the parotid glands, situated just in front of each ear. They extend downward over the angle of the jaw. Parotid saliva, which is mostly watery, travels through Stensen’s duct to empty into the mouth near the upper second molar tooth.
The submandibular glands are positioned beneath the floor of the mouth, under the mandible. These glands are the second largest and produce 60% to 70% of saliva when the mouth is at rest. Secretions travel through Wharton’s duct, opening onto the sublingual caruncle at the base of the tongue.
The smallest major glands are the sublingual glands, located directly beneath the tongue on the floor of the mouth. They produce a thicker, mucous-type secretion, contributing only three to five percent of the total salivary volume. Sublingual glands often release saliva through several small ducts directly into the floor of the mouth.
Essential Functions of Saliva Production
Saliva contains a complex mixture of proteins, minerals, and enzymes that carry out several physiological roles. One primary function is the initial breakdown of food. Saliva contains the enzyme salivary amylase, which begins the digestion of starches and carbohydrates.
Saliva is responsible for lubricating the mouth, which is necessary for comfortable speech and swallowing. The fluid mixes with chewed food to form a soft mass, known as a bolus, making it easier to pass down the esophagus. This lubricating action also protects the delicate mucous membranes lining the mouth from friction and drying out.
Maintaining a balanced oral environment is another important function. Saliva contains bicarbonate and phosphate ions that act as buffers, neutralizing acids produced by bacteria and foods. This buffering capacity helps maintain a neutral pH, minimizing the demineralization of tooth enamel and preventing tooth decay. Saliva also plays an immune defense role, containing antimicrobial agents like lysozyme and immunoglobulins that help control the population of bacteria in the mouth.
Common Conditions Affecting the Glands
The salivary glands are susceptible to several common conditions that can disrupt their normal function. One frequent problem is Sialolithiasis, where calcified deposits, known as salivary stones, form within the gland or its duct. These stones can block the flow of saliva, causing painful swelling that often worsens during meals when saliva production increases.
Another issue is Sialadenitis, which is the inflammation and infection of a salivary gland, typically caused by bacteria. This infection often occurs when a duct is blocked, allowing bacteria to migrate backward into the gland tissue. Viral infections, such as mumps, can also cause Sialadenitis, leading to a painful enlargement, most commonly of the parotid glands.
Xerostomia, or dry mouth, is a symptom indicating a reduction or complete absence of saliva flow. This condition can stem from various causes, including side effects from common medications, such as antihistamines and antidepressants. Xerostomia can also be a symptom of systemic autoimmune disorders, like Sjogren’s syndrome, where the immune system mistakenly attacks the moisture-producing glands.