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 antibacterial 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