The 6-7 meter long tube from pyelolic sphincter to ileocolic sphincter is called small intestine. Here the food stays for 3-5 hours. It is divided into three parts. Duodenum, jejunum and ileum.
(i) Duodenum: The first and U-shaped part of small intestine is called duodenum. Its length is 25-30 cm.
(ii) Jejunum: The tubular part about 2.5 meters long after duodenum is called jejunum.
Function: It digests and absorbs food.
(iii) Ileum: The posterior portion of the jejunum is called the ileum. Its length is three-fifths of the entire small intestine. At the junction of the ileum and the colon is a muscular ring called the ileocolic sphincter.
Function: It has villus like fingers. Increases villus absorption area.