Hello All AIPMT Biology Aspirants. Next in the queue of study material is SALIVARY GLANDS.
Salivary glands release a secretion called Saliva into the oral cavity. Secretion of saliva is called Salivation which keeps the mucous membranes of buccal cavity moist and lubricates the movements of the tongue and lips during speech.
- Three pairs (6 in no.) of major salivary glands are Parotid, Submandibular, and Sublingual.
- Parotid glands (cheeks) are located inferior to ears. Each secretes saliva into the oral cavity via a parotid duct which opens near upper second molar tooth.
- Submandibular glands are found in the floor of the mouth. They are located inferior to the body of the lower jaw or mandible. Submandibular ducts open in oral cavity lateral to the lingual frenulum.
- Sublingual glands are beneath the tongue and superior to the submandibular glands. Their ducts,
open into the floor of the mouth in the oral cavity.
Composition of Saliva
- Saliva is 99.5% water and 0.5% solutes.
- Saliva constitutes solute ions, such as sodium, potassium, chloride, bicarbonate, and phosphate.
- It has enzymes like lysozyme, and salivary amylase.
- It has dissolved gases and various organic substances, like urea and uric acid, mucus, Ig A.
Functions of saliva
- Water in saliva provides a medium for dissolving foods so that they can be tasted by receptors and digestive reactions can begin.
- Chloride ions in the saliva activate salivary amylase.
- Bicarbonate and phosphate ions buffer acidic foods that enter the mouth, so saliva has slightly acidic pH of 6.35–6.85.
- Salivary amylase helps in breakdown of starch present in food.
- Salivary glands also help in removal of waste molecules from the body.
- Mucus helps in lubrication of food so it can be easily chewed in the mouth and swallowed.
- IgA is an antibody which prevents attachment of microbes to the buccal cavity so they cannot penetrate the epithelium of mouth.
- Lysozyme is responsible for killing bacteria present in food.