Digestion and Absorption — BIOLOGY STD 11 Science — Question
Gujarat BoardEnglish MediumSTD 11 ScienceBIOLOGYDigestion and Absorption2 Marks
Question
Explain how digestion takes place in mouth?
✓
Answer
Digestion Process in Mouth: The buccal cavity performs two major functions, mastication of food and facilitation of swallowing. The teeth and the tongue with the help of saliva masticate and mix up the food thoroughly. Mucus in saliva helps in lubricating and adhering the masticated food particles into a bolus. Action of Saliva: The saliva secreted into the oral cavity contains electrolytes $\left( Na ^{+}, K ^{+}, Cl ^{-}, HCO ^{-}\right)$ and enzymes, salivary amylase and lysozyme. The chemical process of digestion is initiated in the oral cavity by the hydrolytic action of the carbohydrate splitting enzyme, the salivary amylase. About 30 percent of starch is hydrolysed here by this enzyme (optimum pH 6.8) into a disaccharide maltose, Lysozyme present in saliva acts as an antibacterial agent that prevents infections.
$\text{Starch}\xrightarrow[\text{pH}6.8\ \ ]{\text{Salivary Amylase}\ \ }\text{Maltose}$
The bolus is then conveyed into the pharynx and then into the oesophagus by swallowing or deglutition. The bolus further passes down through the oesophagus by successive waves of muscular contractions called peristalsis. The gastro oesophageal sphincter controls the passage of food into the stomach.
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