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
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.
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
