VPB 121: Veterinary Physiology - II (2+1)

FUNCTIONS OF THE SALIVA

• Saliva has lubricating function that facilitates the mastication and swallowing of ingested food.
• The mucin content provides an adhesive to food to form bolus for swallowing.
• Water soluble components of food get dissolved in saliva which gain access to the taste buds to distinguish different tastes which in turn produces large quantity of saliva.
• Spontaneous secretion of saliva even during sleep has an important protective function by keeping oral mucosa moist and lubricated even in the absence of food.
• Increased secretion during eating also enhanced protection to the mucosa and serous layer by diluting harmful substances.
• Pronounced salivary secretion prior to vomiting protects the mucous membrane during subsequent passage of acid vomitus
• Saliva of pig, rabbit, dog and man contain an amylolytic enzymes ptyalin or salivary amylase that hydrolyses alpha 1_4, glucosidic linkages of the statch and leads to the formation of series of dextrin which are finally broken down to maltose (87%) and glucose (13%).
• Salivary amylase is absent in horse, cattle, sheep and goat.
• The optimum hydrogen ion concentration for salivary amylase is around pH 6.2; it is active over a wide range of pH and continues its digestive action in the stomach. Most of the carbohydrates are partly brokendown by salivary amylase in the stomach. In man, amylolytic activity continue up to 30mintues after the entry food into the stomach.
• Many other enzymes like lipase, maltase, peroxidase, mucolytic enzymes are also found in saliva, but they are derived from the bacteria normally residing in the mouth or from the break down of desquamated cells from the buccal mucosa .
• Young animals have another enzyme, lingual lipase, for hydrolysing the fat
• Saliva possesses bacteriostatic properties due to the presence of lysozyme to dissolve bacteria
• Saliva is aslo involved in thermoregulation as evoprative heat loss, and is significant in dogs and cats.

Functions of ruminant saliva

• Excellent buffer due to rich contents of bicarbonate and phosphate ions with pH of 8.10
• In ruminants , saliva provides a proper media for the bacterial growth and activity in the rumen.
• HCO₃ and PO₄ content of saliva neutralize the Volatile fatty acids produced during microbial fermentation.
• Urea is a non protein source supplies nitrogen for the bacterial growth and microbial protein synthesis
• Phosphates are utilized for nucleoprotein and phospholipid synthesis.
• Mucin content of saliva has anti-foaming characteristic and reduces foaming tendency of the diet.