Small intestine is composed of three parts which are as follows.
- Duodenum (twelve-finger intestine) is the inferior section of small intestine with about 25 cm in length, U-Shape, and an end section of gall bladder and pancreas.
- Jejunum (empty intestine ) is the central section of small intestine with the length of about 7m.
- Lleum (absortion intestine ) is the final section of small intestine with the length of about 1 m.
A cross section of small intestine illustrates a microscopic composition of digestive tract
|The structure of small intestine and villi that function in nutrient absorption|
The composition from outward to inward consecutively is outer membrane (serosa layer), smooth muscle layer, vascular tissue layer (submucose layer), and mucosa layer.
Food movement in small intestine is cauused by contraction of muscular lining on small intestine.The contraction causes segmentation and peristaltic movement. Segmentation is a squeezing motion along the tract to blend the chyme.
In mucosa epithelium, there are a lot of goblet cells producing mucose to smoothen food and protect the intestine from chemical injury. In mucosa there is also found villi.
The food that enters small intestine is in the form of liquid particles (chyme). Hydrochloride acid (HCI) that also gets into the small intestine stimulates the glands in the intestine wall to produce secretin hormone (controlling the secretion of Pancreatic juice) and cholecystokinin hormone ( controlling the secretion of bile) Pancreatic juice and bile are then transferred through choledochal duct that ends in duodenum. The breaking down resulted by pancreatic juice and bile will be absorbed by absortion cells.
Various of peptidase, such as pepsin, trypsin, and chymotrypsin work together in the breaking down of protein molecules. Lipid that is emulsified by bile salt is broken down by lipase into fatty acid and glycerol. The result are particles that can be absorbed by the intestine derectly.
Food from stomach goes to the intestine. Intestine is a tract to digest food, absorb nutrients, and as a site for fermentation and waste decomposition by bacteria.
|The Structure of Intestine and anus in human|
Human has two types of intestine
- small intestine (intestinal tenue )
- large intestine (intestinal crassum )
source:biology, Concept and connection, 2006