Where does most absorption of digested foods occur? Describe the structural adaptations that give the small intestine its great absorptive area.
Most absorption of digested foods occurs in the small intestine. From the stomach, food passes into the duodenum portion of the small intestine and, then, into the very long, coiled section of the small intestine. The total length of the small intestine in adult men averages over twenty feet. The great length of the small intestine is but one adaptation it possesses aimed at increasing the absorptive surface area of its lumen. The mucosa lining of the small intestine has many folds and ridges which are lined by finger-like outgrowths, called villi. Each villus, in turn, is lined by innumerable microvilli. Absorption of simple sugars and amino acids across the cell membranes of the microvilli involves active transport.
