CBSE Class 9 Answered

Absorption of food mainly takes place in ileum where digestion is complete (by diffusion & active transport). Ileum is adapted in the following manner to facilitate absorption of food:

i) The wall of ileum is muscular so that waves of contraction (peristalsis) can mix the food and push it forward.  Circular folds of the mucosa and submucosa linings of the small intestine force the food to spiral through it and slow down the movement, allowing more effective absorption.

ii) Numerous fingerlike projections, or villi, point inwards from the wall, increasing the surface area available for absorption. Villi bear microvilli on the epithelium, which again increase the surface area.

iii) The ileum has an excellent blood supply, which receives the food molecules passing through the wall and transports them to various parts of the body.

iv) Ileum is quite long. The longer the food is within the ileum, the more nutrients can be absorbed.