Small intestine is lined by epithelium which is specialised to absorb. It has mechanisation to increase its absorbing surface area several times,

(i) Villi: They are transverse folds of intestine wall that not only increase surface area but also reach deep into the lumen of intestine for absorption of digested food. Villi possess blood capillaries and lacteals (lymph vessels) for quick transport of absorbed food,

(ii) Microvilli: The columnar cells of the intestinal epithelium have fine microscopic outgrowths called microvilli. Microvilli increase the surface area of epithelial cells.