Transcript Stomach Anatomy

Stomach Anatomy
Anatomy
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The stomach is Jshaped, baglike organ
that expands to store
food
Appears in week 5.
A pliable, saccular
organ.
Located in the LUQ
and epigastrium.
Separated from the GI
tract (2 locations).
Gross Anatomy
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Proximal= Cardia
(attaches to
esophagus) attaches
at the LES.
Fundus= most
superior portion,
receives food.
Body= largest portion,
contains parietal, chief
and ECL cells.
Distal= antrum,
contains the G cells.
Histologically
The stomach is almost entirely covered with peritoneum.
 The peritoneum forms the outer gastric serosa.
 Beneath the serosa is the muscularis propria (MP).
 The MP is made up of 3 layers of smooth muscle.
1. inner oblique layer: This layer is responsible for
creating the motion that churns and physically breaks
down the food.
It is the only layer of the three which is not seen
in other parts of the digestive system. The antrum
has thicker skin cells in its walls and performs more
forceful contractions than the fundus.
2. The middle layer is the circular muscle
and is the only “complete” layer of
muscle
 As you progress distally the middle layer of
muscle begins to thicken and form the Pylorus
Which functions as a true sphincter.
 This and the GE junction form the gastric
“borders” and are the two “fixed” points of the
stomach.
3.
The outer muscle layer (longitudinal) is
contiguous with the outer layer of the
esophagus.
Within the layers of the MP, there is a rich
plexus of autonomic nerves and ganglia .
 The submucosa lies between the MP and
the mucosa. It is a collagen rich layer of
connective tissue and is the
weakest/strongest layer of the gastric wall.
 The submucosa also contains the rich
blood vessel network and the lypmhatics
as well as Meissner’s plexus.
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The mucosa consists of 3 layers:
 Surface epithelium (columnar).
 Lamina propria
○ Connective tissue layer that supports the
surface epithelium.
 Muscularis mucosae (probably the reason
for rugal folds).
○ The MM is the boundary for
invasive/noninvasive gastric cancer.
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The stomach presents two openings, two borders
or curvatures, and two surfaces.
Openings.—The opening by which the esophagus
communicates with the stomach is known as the
cardiac orifice, and is situated on the left of the
middle line at the level of the tenth thoracic vertebra.
The short abdominal portion of the esophagus
(antrum cardiacum) is conical in shape and curved
sharply to the left, the base of the cone being
continuous with the cardiac orifice of the stomach.
The right margin of the esophagus is continuous with
the lesser curvature of the stomach, while the left
margin joins the greater curvature at an acute angle,
termed the incisura cardiaca.
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The pyloric orifice communicates with
the duodenum, and its position is usually
indicated on the surface of the stomach
by a circular groove, the
duodenopyloric constriction. This
orifice lies to the right of the middle line
at the level of the upper border of the
first lumbar vertebra.
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Curvatures.—The lesser curvature (curvatura
ventriculi minor), extending between the cardiac and
pyloric orifices, forms the right or posterior border of the
stomach. It descends as a continuation of the right
margin of the esophagus in front of the fibers of the right
crus of the diaphragm, and then, turning to the right, it
crosses the first lumbar vertebra and ends at the
pylorus. Nearer its pyloric than its cardiac end is a wellmarked notch, the incisura angularis, which varies
somewhat in position with the state of distension of the
viscus; it serves to separate the stomach into a right and
a left portion. The lesser curvature gives attachment to
the two layers of the hepatogastric ligament, and
between these two layers are the left gastric artery and
the right gastric branch of the hepatic artery.
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The greater curvature (curvatura ventriculi
major) is directed mainly forward, and is four
or five times as long as the lesser curvature.
Starting from the cardiac orifice at the incisura
cardiaca, it forms an arch backward, upward,
and to the left; the highest point of the
convexity is on a level with the sixth left costal
cartilage. From this level it may be followed
downward and forward, with a slight convexity
to the left as low as the cartilage of the ninth
rib; it then turns to the right, to the end of the
pylorus.
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Directly opposite the incisura angularis of
the lesser curvature the greater curvature
presents a. dilatation, which is the left
extremity of the pyloric part; this dilatation
is limited on the right by a slight groove, the
sulcus intermedius, which is about 2.5
cm, from the duodenopyloric constriction.
The portion between the sulcus
intermedius and the duodenopyloric
constriction is termed the pyloric antrum.
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At its commencement the greater
curvature is covered by peritoneum
continuous with that covering the front of
the organ. The left part of the curvature
gives attachment to the gastrolienal
ligament, while to its anterior portion are
attached the two layers of the greater
omentum, separated from each other by
the gastroepiploic vessels.
Surfaces.—When the stomach is in the contracted
condition, its surfaces are directed upward and
downward respectively, but when the viscus is
distended they are directed forward, and backward.
They may therefore be described as anterosuperior
and postero-inferior.
 Antero-superior Surface.—The left half of this surface
is in contact with the diaphragm, which separates it
from the base of the left lung, the pericardium, and the
seventh, eighth, and ninth ribs, and intercostal spaces
of the left side. The right half is in relation with the left
and quadrate lobes of the liver and with the anterior
abdominal wall. When the stomach is empty, the
transverse colon may lie on the front part of this
surface. The whole surface is covered by peritoneum.
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The Postero-inferior Surface is in relation with the
diaphragm, the spleen, the left suprarenal gland, the
upper part of the front of the left kidney, the anterior
surface of the pancreas, the left colic flexure, and the
upper layer of the transverse mesocolon. These
structures form a shallow bed, the stomach bed, on
which the viscus rests. The transverse mesocolon
separates the stomach from the duodenojejunal
flexure and small intestine. The postero-inferior
surface is covered by peritoneum, except over a
small area close to the cardiac orifice; this area is
limited by the lines of attachment of the
gastrophrenic ligament, and lies in apposition with
the diaphragm, and frequently with the upper portion
of the left suprarenal gland
Cell Types, 1
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Parietal:
 Location: Body
 Function: secrete acid and intrinsic factor
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Mucus:
 Location: Body, Antrum
 Function: mucus production
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Chief:
 Location: Body
 Function: produce Pepsin
Cell Types, 2
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Surface epithelium:
 Location: Diffuse
 Function: produce mucus, bicarb,
prostaglandins(?)
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ECL:
 Location: Body
 Function: Histamine production
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G cells:
 Location: Antrum
 Function: Gastrin production
Cell Types,3
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D cells:
 Location: Body, Antrum
 Function: produce Somatostatin
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Gastric mucosal interneurons:
 Location: Body, Antrum
 Function: produce Gastrin-releasing peptide
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Entric Neurons:
 Location: Diffuse
 Function: CGRP, others production
The stomach serves a variety of
functions:
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Storage. Because of its accordion like folds
(called rugae), the wall of the stomach can
expand to store two to four liters of material.
Temporary storage is important because you
eat considerably faster than you can digest
food and absorb its nutrients.
Mixing. The stomach mixes the food with
water and gastric juice to produce a creamy
medium called chyme.
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Physical breakdown. Three layers of
smooth muscles (rather than the usual
two) in the muscularis externa churn the
contents of the stomach, physically
breaking food down into smaller
particles. In addition, HCl denatures (or
unfolds) proteins and loosens the
cementing substances between cells (of
the food). The HCl also kills most
bacteria that may accompany the food.
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Chemical breakdown. Proteins are chemically
broken down by the enzyme pepsin. Chief
cells, as well as other stomach cells, are
protected from self-digestion because chief
cells produce and secrete an inactive form of
pepsin, pepsinogen. Pepsinogen is converted
to pepsin by the HCl produced by the parietal
cells. Only after pepsinogen is secreted into
the stomach cavity can protein digestion
begin. Once protein digestion begins, the
stomach is protected by the layer of mucus
secreted by the mucous cells.
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Controlled release. Movement of chyme
into the small intestine is regulated by a
valve at the end of the stomach, the
pyloric sphincter.
Arterial Supply
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The stomach is supplied by many arteries :
1- short gastric arteries - branches of the splenic artery supply the fundus of stomach
2-left gastro epiploic artery - branch of the splenic artery
- supply the greater curvature of the stomach .
3- left gastric artery which is a direct branch of the
coeliac trunk that arises from the aorta . supplies the
lesser curvarture.
4- right gastric artery which is a branch of the common
hepatic artery - supplies the lesser curvature.
5- right gastro epiploic artery which is a branch of the
gastro duodenal artery which is again a branch of the
common hepatic artery- supplies the greater curvature
Arterial Supply
Venous Drainage
Lymphatic Drainage
Nerve Supply
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The vagus nerve is composed of both
motor and sensory fibers, and has a
more extensive course and distribution
than any of the other cranial nerves,
since it passes through the neck and
thorax to the abdomen.
Nerve Supply
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Branches of Distribution.—The branches
of distribution of the vagus are:
In the Jugular Fossa… Meningeal.
Auricular.
In the Neck………… Pharyngeal. Superior
laryngeal. Recurrent. Superior cardiac.
In the Thorax………. Inferior cardiac.
Anterior bronchial. Posterior bronchial.
Esophageal.
In the Abdomen……. Gastric. Celiac.
Hepatic.
Nerve Supply
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The Gastric Branches (rami gastrici) are distributed
to the stomach. The right vagus forms the posterior
gastric plexus on the postero-inferior surface of the
stomach and the left the anterior gastric plexus on
the antero-superior surface. The Celiac Branches
(rami cæliaci) are mainly derived from the right
vagus: they join the celiac plexus and through it
supply branches to the pancreas, spleen, kidneys,
suprarenal bodies, and intestine. The Hepatic
Branches (rami hepatici) arise from the left vagus:
they join the hepatic plexus and through it are
conveyed to the liver.
Nerve Supply
Thanks
for your
attention