Download SMALL INTESTINE

SMALL INTESTINE
SMALL INTESTINE
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
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Terminal part of GIT before it opens into
the large intestine.
4 – 6 meters in length.
Absorption – main function
Divided into 3 parts:
 Duodenum
 Jejunum
 Ileum
FEATURES FAVOURING
ABSORPTION
 Extremely long – permits prolonged contact
between food and enzymes and also digested
products and absorptive cells
 Plicae circularis OR Valve of Kerkring –
permanent folds of mucous membrane unlike
rugae
 Villi on plicae circularis
 Microvilli on the enterocytes – cytoplasmic
extensions
GENERAL HISTOLOGICAL
PATTERN OF GIT
From inwards out 4 layers are present:
1. Mucosa
2. Sub mucosa
3. Muscularis externa
4. Serosa OR Adventitia
GENERAL HISTOLOGICAL PATTERN OF GIT

1.
i.
ii.
iii.
From inwards out 4 layers are present:
Mucosa- consists of :
Lining epithelium – simple columnar cells with striated
border.
Layer of connective tissue- lamina propria
Muscularis mucosa- smooth muscles
All the above are thrown into folds called ‘villi’
2. Sub mucosa- loose areolar tuissue
3. Muscularis externa – inner circular and outer
longitudinal smooth muscles
4. Serosa OR Adventitia
MUCOSA
Lining epithelium –
Absorptive enterocytes
Goblet cells - mucous secreting
Paneth cells – basally placed exocrine serous
cells having zymogen granules.
4. Argentaffin cells - stimulates smooth muscles
by secreting 5 HT.
5. Crypts of Liberkuhn – invagination of lining
epithelium forming simple tubular glands.
Basal cells are proliferating cells.

1.
2.
3.
 Lamina propria – connective tissue
containing blood vessels and lymphoid
nodules.
 Muscularis mucosa – smooth muscle layer
contraction of which results in mixing of
food.
DUODENUM
 C shaped initial smallest portion of the small
intestine
 Connects stomach to jejunum
 Villi – long, broad, leaf like and numerous
 Lamina propria- crypts of
Lieberkuhn(STRAIGHT TUBULAR GLANDS)
 Sub mucosa – Brunners gland: The identifying
feature of duodenum are mucous acini (tubulo
alveolar glands) whose duct open into crypts of
liberkuhn. The secretion contains bicarbonate
and mucous.
 Lymphatic nodules are also seen sometimes.
JEJUNUM
 Connects duodenum to ileum
 Follows the basic histological pattern of
GIT
 Villi are smaller and less numerous
 Goblet cells increase in number
 Solitary lymph nodules present
ILEUM
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Connects jejunum to large intestine
Fingerlike, smaller and fewer villi
Much more goblet cells seen
Payer’s patches in the sub mucosa also
called intestinal tonsils are the identifying
features.
IDENTIFICATION OF DUODENUM,
JEJUNUM AND ILEUM
DUODENUM
JEJUNUM
ILEUM
Large, broad,
leaf like villi
Finger shaped
villi.
Fewer, shorter and
irregular villi.
Goblet cells in
large numbers
Brunners gland
in sub mucosa
LARGE NUMBER OF
Payer’s patch in
sub mucosa
GOBLET CELLS in
mucosa
INTRINSIC NERVE SUPPLY
 Myenteric plexus of Auerbach in
muscularis externa.
 plexus of Meissner’s – in the sub mucosa.