Transcript stomach


The stomach
functions both as a
reservoir and as a
digestive organ. It
empties its
contents in small
portions (suitable
for continued
digestion) into the
small intestine
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cardiac part,
fundus,
body
pyloric part
(pyloric antrum
and pyloric
canal)
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The cardiac sphincter
is a specialized valve
found between the
esophagus and the
stomach. It prevents
backflow of food and
digestive enzymes.
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The is the frontal
region of the
stomach. It begins
digestion of
proteins and mixes
together stomach
contents.
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The body is the
central region of
the stomach. It
also digests
proteins and
blends materials
found in
stomach.
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The pylorus is the back
region of the stomach. It
contracts to empty
materials from the
stomach into the small
intestine
The pyloric sphincter is a
specialized valve that
prevents materials and
digestive enzymes from
escaping into the small
intestine before digestion
is completed in the
stomach.
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Rugae are found
on the interior
layer of the
stomach and aid
in breaking down
food when the
stomach
contracts.
Gastric areas (mammillated
areas).
Mucosa is divided by furrows
into small irregular
elevations. These are the
gastric areas.
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Gastric pits (foveolae).
surface of each gastric area to
be studded with minute
depressions, the gastric pits.
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Epithelium
Simple columnar
 Lamina Propria
contains glands which
differ in each
histological region of
the stomach.
 Muscularis Mucosae.
It measures from 0.31.5 mm in thickness,
being thinnest in the
cardia and thickest in
the body and fundus.
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This layer separates
the muscularis from
the mucosa .
It consists of coarse
collagenous fibers
and many elastic
fibers, plus blood
vessels, lymph
vessels, nerves, and
the plexus of
Meissner. Glands are
absent.
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an outer longitudinal,
a middle circular,
and an inner oblique.
The oblique layer is best developed in the cardia
and body. The circular layer is thickest in the
pylorus where it forms the pyloric sphincter,
which helps control the evacuation of food. The
longitudinal layer is continuous with the
longitudinal muscle layer of the esophagus and
duodenum. The myenteric plexus lies in the
connective tissue lamina, which separates the
circular from the longitudinal muscle fibers.
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The outer layer
consists of loose
connective tissue
covered on its
superficial aspect
by
mesothelium. Smal
l blood vessels,
lymphatics, and
nerves lie in the
connective tissue.
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surface epithelium (simple,
tall columnar).
It contains mucusproducing cells, surface
mucous cells,
The mucus is alkaline and
adheres to the epithelium.
which protects the mucosa
from the acidic contents of
the stomach.
 cellular
composition
and function
of the gastric
glands are
specialized in
the different
parts of the
stomach
- Secrete mucus to protect
epithelial cells from enzymes
& acid
- Secrete HCl (for protein
digestion) & intrinsic factor (for
B12 absorption)
- Secrete pepsinogen which
gets converted to “pepsin”
when mixed with HCl; for
protein digestion
Entero-
- Secrete gastrin to regulate
stomach emtying
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Cardiac glands are
heavily branched
tubular glands
which contain
mainly mucusproducing cells.
Shallow Gastric Pits
Short glands
Each glandular
tubule
consists of
three parts:
 deep body,
 intermediary
neck
 upper
isthmus.
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Branched, coiled
tubular glands.
Endocrine cells, in
particular gastrinproducing cells, are
more frequent than in
principal glands. A
few parietal cells may
be present but chief
cells are usually
absent.
In the pylorus, the
pits extend
downward to
about one-half
the thickness of
the mucosa;
 in the cardia, and
fundus, the pits
occupy only onefourth the
thickness of the
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are found between
the parietal cells in
the neck of the
gland.
They are difficult to
distinguish from
chief cells in plain
H&E stained
section
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contain Zymogens
granules
Abundant RER give
the cell Basophilic
stain
most numerous of
the four types.
They occur
primarily in the
body of the glands.
produce
pepsinogen, which
is a precursor of
the proteolytic
enzyme pepsin.
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Large acidophilic cells.
secrete the
hydrochloric acid of the
gastric juice. Aside
from activating the
pepsinogen
Parietal cell also secrete
intrinsic factor, which is
necessary for the
resorption of vitamin
B12
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Scattered between the
epithelial cells of the gastric
mucosa and their basement
membrane.
Demonstrated by Electron
microscope or by
Immunological
technique.On light
microscopy they appear
clear.
Secretion is released in the
lamina propria and
distributed by blood
vessels.
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The best characterized endocrine cells in the
gastric mucosa are gastrin-producing cells (G
cells) and somatostatin-producing cells (D
cells). G cells are most frequent in the middle
third of the glands. They stimulate the
secretion of acid and pepsinogen. G cell
function is stimulated by nervous input, the
distension of the stomach.
D cells are found mainly in glands of the
pyloric antrum. They inhibit G cells and
thereby acid production. D cell function is
stimulated by acid in the lumen of the
stomach and duodenum.
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The surface epithelium
is renewed
approximately every
third day.
The source of the new
cells is the isthmus, i.e.
the upper part of the
neck, of the gastric
glands, where cells
divide and then
migrate towards the
surface epithelium and
differentiate into
mature epithelial cells