Digestion And Absorption

The finger-like projections described are the villi of the small intestinal mucosa, and their cells additionally bear microvilli on their free surface. NCERT Class 11, Chapter 16 (Digestion and Absorption) emphasises that villi and microvilli together produce an enormous absorptive surface area, allowing efficient uptake of the end products of digestion such as glucose, amino acids, fatty acids and glycerol. Each villus is richly supplied with blood capillaries and a lacteal, so absorbed nutrients are immediately carried into the circulation or lymph. Secretion of hydrochloric acid is incorrect because HCl is produced by oxyntic (parietal) cells of the gastric glands in the stomach, not by intestinal villi. Mechanical churning of food is achieved by muscular contractions of the stomach and peristalsis, not by mucosal folds. Storage of undigested cellulose does not occur in the small intestine; cellulose passes largely undigested to the large intestine, where it adds roughage. The defining role of villi is therefore absorptive. A sanity check supports this: organs specialised for absorption universally maximise surface area, exactly as the villi and microvilli accomplish in the small intestine.