Digestion and Absorption — Bio Zoology STD 11 — Question
Tamilnadu BoardEnglish MediumSTD 11Bio ZoologyDigestion and Absorption5 Marks
Question
Explain the digestion in the buccal cavity.
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Answer
The smell, sight, and taste as well as the mechanical stimulation of food in the mouth, triggers a reflex action which results in the secretion of saliva. Mechanical digestion starts in the mouth by grinding and chewing food. It is called mastication. The saliva contains water, electrolytes ( $Na ^{+}, K ^{+}, Cl ^{-}$and $HCO _3$ ), salivary amylase (ptyalin), antibacterial agent lysozyme, and a lubricating agent mucus (a glycoprotein). The mucus in saliva prepares the food for swallowing by moistening, softening, lubricating, and adhering the masticated food into a bolus.
About 30 percent of polysaccharides, starch is hydrolyzed by the salivary amylase enzyme into disaccharides (maltose). The bolus is then passed into the pharynx and then into the oesophagus by swallowing or deglutition. The bolus further passes down through the oesophagus to the stomach by successive waves of muscular contraction called peristalsis. The gastro oesophageal sphincter controls the passage of food into the stomach.
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