Saliva is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is 98% water plus electrolytes, mucus, white blood cells, epithelial cells, enzymes, antimicrobial agents such as secretory IgA, and lysozymes.
The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands, as well as hundreds of minor salivary glands. Salivary glands can be classified as serous, mucous, or seromucous (mixed).
The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the mandibular ramus, and secretes serous saliva through the parotid duct into the mouth, to facilitate mastication and swallowing and to begin the digestion of starches. There are also two other types of salivary glands; they are submandibular and sublingual glands. Sometimes accessory parotid glands are found close to the main parotid glands.
The paired submandibular glands are major salivary glands located beneath the floor of the mouth. They each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimulation their contribution decreases in proportion as the parotid secretion rises to 50%. The average length of the normal human submandibular salivary gland is approximately 27mm, while the average width is approximately 14.3mm.
Parotitis is an inflammation of one or both parotid glands, the major salivary glands located on either side of the face, in humans. The parotid gland is the salivary gland most commonly affected by inflammation.
The submandibular duct or Wharton duct or submaxillary duct, is one of the salivary excretory ducts. It is about 5 cm. long, and its wall is much thinner than that of the parotid duct. It drains saliva from each bilateral submandibular gland and sublingual gland to the sublingual caruncle at the base of the tongue.
Sialolithiasis, is a condition where a calcified mass or sialolith forms within a salivary gland, usually in the duct of the submandibular gland. Less commonly the parotid gland or rarely the sublingual gland or a minor salivary gland may develop salivary stones.
Carbonic anhydrase II, is one of sixteen forms of human α carbonic anhydrases. Carbonic anhydrase catalyzes reversible hydration of carbon dioxide. Defects in this enzyme are associated with osteopetrosis and renal tubular acidosis. Renal carbonic anhydrase allows the reabsorption of bicarbonate ions in the proximal tubule. Loss of carbonic anhydrase activity in bones impairs the ability of osteoclasts to promote bone resorption, leading to osteopetrosis.
Carbonic anhydrase 3 is an enzyme that in humans is encoded by the CA3 gene.
Carbonic anhydrase IX is an enzyme that in humans is encoded by the CA9 gene. It is one of the 14 carbonic anhydrase isoforms found in humans and is a transmembrane dimeric metalloenzyme with an extracellular active site that facilitates acid secretion in the gastrointestinal tract. CA IX is overexpressed in many types of cancer including clear cell renal cell carcinoma (RCC) as well as carcinomas of the cervix, breast and lung where it promotes tumor growth by enhancing tumor acidosis.
Carbonic anhydrase 1 is an enzyme that in humans is encoded by the CA1 gene.
Carbonic anhydrase 4 is an enzyme that in humans is encoded by the CA4 gene.
Histatin 3, also known as HTN3, is a protein which in humans is encoded by the HTN3 gene.
Carbonic anhydrase 12 is an enzyme that in humans is encoded by the CA12 gene.
Statherin is a protein in humans that is encoded by the STATH gene. It prevents the precipitation of calcium phosphate in saliva, maintaining a high calcium level in saliva available for remineralisation of tooth enamel and high phosphate levels for buffering.
Carbonic anhydrase 14 is an enzyme that in humans is encoded by the CA14 gene.
Carbonic anhydrase 7 (CA7) is an enzyme that in humans is encoded by the CA7 gene.
Salivary gland diseases (SGD) are multiple and varied in cause.
The carbonic anhydrases form a family of enzymes that catalyze the interconversion between carbon dioxide and water and the dissociated ions of carbonic acid. The active site of most carbonic anhydrases contains a zinc ion. They are therefore classified as metalloenzymes. The enzyme maintains acid-base balance and helps transport carbon dioxide.
Carbonic anhydrase 13 is a protein that in humans is encoded by the CA13 gene.
