SMALL INTESTINE

Dr IramTassaduq

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 submucosa.

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

• are absent from the first few centimetres 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.

MICROVILLI

INTESTINAL GLANDS

INTESTINAL CELLS

ENTEROCYTES

GOBLET CELL

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 secretory 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-secretory appearance, with basophilic basal cytoplasm (containing protein-synthetic rough endoplasmic reticulum) and apical secretory vesicles (zymogen granules).

ENTEROENDOCRINE CELLS

ENTEROENDOCRINE CELLS

• Concentrated in lower portion of intestinal gland

• Produce a lot of peptide hormones

COMPARISON