Salivary gland: The salivary glands consist of numerous round or oval sacs. The cyst wall consists of serous cells and mucous cells. There are three pairs of salivary glands in the mouth. These are-
1. Sublingual Glands: A pair of sublingual glands are located under the tongue. It consists of numerous round or oval sacs. Each sac has a duct in the center. The ducts join together to form the main duct. It contains mammary cells. Serous cells and mucous cells. Serous cells secrete tylin and maltase and mucous cells secrete mucin.
2. Sub mandibular/maxillary glands: The lower jaw has a pair of sub mandibular glands. Each gland opens on the side of the frenulum of the tongue through the duct of Warton.
3. Parotid Gland: It is the largest salivary gland. A total of one pair of parotid glands are located under both ears. Each gland opens into the vestibule through Stensen’s duct. Mumps causes swelling and painful inflammation of the parotid gland due to viral infection.
Salivary juice
(i) Water: Red juice contains 95.5-99.5% water.
(ii) Cellular components: Saliva contains leukocytes, epithelial cells, protozoa, bacteria, yeast etc.
(iii) Gaseous component: 50 ml of carbon dioxide, 2.5 ml of nitrogen and 1 ml of oxygen are dissolved in every 100 ml of saliva.
(iv) Biomaterials: Saliva contains amino acids, cholesterol, vitamins, antigens, antibodies, mucin, urea, haptocorin, apiorphin, enzymes (tyalin, lipase, maltase, lysozyme, phosphatase, carbonic anhydrase) etc.
(v) Inorganic substances: Red blood contains sodium chloride, sodium phosphate, potassium chloride, potassium thiocyanate, calcium carbonate, calcium phosphate etc.
Function of salivary juice
Saliva is secreted from salivary glands. Lalars contains 95.5% water and 0.5% electrolytes and protein. A person secretes 1200-1500 ml of saliva every day. When the secretion of saliva is reduced, the lips become dry, a condition known as xerostomia.
(i) Taste: Saliva helps the tongue to taste. People with low salivation suffer from dysgeusia.
(ii) Softening and liquefying of food: Mucin in saliva softens and liquefies the food.
(iii) Destruction of microbes: Lysozyme destroys bacteria or microbes.
(iv) Food digestion: Tylin and maltase enzymes digest sugary food.
(v) Dehydration: When the body becomes dehydrated, salivary secretion decreases and thirst is felt. Water balance is maintained by drinking water.
(vi) As a buffer: Mucin present in saliva, bicarbonate and phosphate act as buffers.
(vii) Excretion: Urea, heavy metals, thiocyanate, antibiotics, morphine, ethyl alcohol etc. are excreted from the body through saliva.