Small intestine
- 1. SMALL INTESTINE AND VILLUS Sathyananthinee.s Natural science
- 2. 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
- 3. SMALL INTESTINE • The small intestine is divided • duodenum • jejunum • ileum.
- 4. 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.
- 5. 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.
- 6. ILEUM • The ileum is the last section of the small intestine and spans about 6 feet. Its function is to absorb water and vitamins.
- 7. 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
- 8. MUCOSA
- 9. 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.
- 10. 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.
- 13. INTESTINAL CELLS
- 14. 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 .
- 15. 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.
- 16. PANETH CELLS • Paneth cells have typical serous-secretary appearance, with basophilic basal cytoplasm (containing protein-synthetic rough endoplasmic reticulum) and apical secretary vesicles granules).
- 17. ENTEROENDOCRINE CELLS • Concentrated in lower portion of intestinal gland • Produce a lot of peptide hormones
- 18. 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.
- 19. 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