Small Intestine

Biology

definition

Small intestine

Structure:
The small intestine has three sub-regions:
  • Duodenum: C- shaped
  • Jejunum: A long coiled middle portion 
  • Ileum: Highly coiled. It opens in the large intestine. 
The walls of the small intestine have finger-like foldings called villi. The cells which line the villi produce many small projections called microvilli. 
Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal. 
Mucosa epithelium has goblet cells. They secrete mucus which helps in lubrication. Mucosa also forms crypts in between the bases of villi in the intestine (crypts of Lieberkuhn).
Functions:
  • It serves for both digestion and absorption.
  • It receives two digestive juices; the bile and pancreatic juice.
  • Ileum is very long, has large villi and made up of single epithelium, which helps in absorption of food.

definition

Lacteal

A lacteal is a lymphatic vessel. It is present in a villus of the small intestine. Its function is to move lymph through the intestines. This can help to keep lymph circulating through the small intestine. They also help in transferring nutrients from the small intestine into the blood. Fats in the form of chylomicrons are transported into the lacteals by exocytosis.