SMALL INTESTINE AND VILLUS

Sathyananthinee.sNatural science

INTRODUCTION• small intestine is a tube of about 2.5 cm wide.• As it is too long, it lies coiled and folded in the

abdominal cavity.• Food particles move only very slowly through this small

intestine.• There are a number of blood vessels in the small

intestine.• Within these infolding finger like projections called villi.• These villi enhance the absorptive capacity of the small

intestine

SMALL INTESTINE

• The small intestine is divided

• duodenum • jejunum • ileum.

THE DUODENUM

• The duodenum is the first section of the small intestine and has a thicker layer of tissue than the other areas of the small intestine.

• It neutralizes stomach acids and breaks down carbohydrates and fats. The duodenum is about 2 feet long.

JEJUNUM

• The jejunum is the main section of the small intestine. It covers about 15 feet and is responsible for the absorption of almost all nutrients except water.

ILEUM

• The ileum is the last section of the small intestine and spans about 6 feet. Its function is to absorb water and vitamins.

PLICAE CIRCULARES • (valves of Kerkering) are

macroscopically visible, crescent-shaped folds of the mucosa and sub mucosa.

• permanent structures, i.e. their presence does not depend on the state of distension of the small intestine.

• are absent from the first few centimeters of the duodenum and the distal part of the ileum.

• well developed in the jejunum. • increase the surface area of the

mucosa

MUCOSA

INTESTINAL VILLI• The entire intestinal mucosa

forms intestinal villi (about one mm long), which increase the surface area by a factor of ten.

• The surface of the villi is formed by a simple columnar epithelium.

ABSORPTION OF NUTRIENTS

• Within each Digested fats are transported through small vessels called lacteals.

• The digested fats are transported into the lymphatic system, and from there into the bloodstream.

• villus is a network of tiny blood vessels called capillaries.• All nutrients, except digested fats, enter the bloodstream

through the capillaries.

Villi and Microvilli

INTESTINAL GLANDS

INTESTINAL CELLS

GOBLET CELLS

• The apical end of each goblet cell is occupied by a large mass of mucus, which compresses adjacent cells.

• The nucleus toward the basal end of the cell.

• Attached by junctional complexes (evidenced in light microscopy as the "terminal bar") to adjacent absorptive cells .

PANETH CELLS

• Paneth cells are secretary epithelial cells located at the ends of intestinal crypts.

• The function for these cells is secretion of anti-bacterial proteins into the crypt lumen, thereby providing protection for the stem cells which line the crypt walls.

PANETH CELLS

• Paneth cells have typical serous-secretary appearance, with basophilic basal cytoplasm (containing protein-synthetic rough endoplasmic reticulum) and apical secretary vesicles granules).

ENTEROENDOCRINE CELLS

• Concentrated in lower portion of intestinal gland

• Produce a lot of peptide hormones

CONCLUSION

• The digestion of food is completed in the small intestine.• The absorption of food particles take place mainly in the

small intestine.• The structure of the small intestine is suitable for the

absorption of food particles.• Finger like project into the lumen of small intestine are

called villi.

REFERENCE

• Dr. B.B. Arora and A.K Sabharwal(2010): A text book of biology std .XII, Modern publication

• Dr . E. Valsala Kumar (2004): A text book of botany , Trivandrum publication

• Kumar Pushkar and Dr A.P.Singh (2011): A text book of CSIR-UGC Life science, Upkar publication