The Stomach

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Oesophagus | Main Anatomy Index | The
duodenum
Last updated 30 March 2006
The Stomach
- The stomach is the most dilated part of the alimentary canal.
- It is located between the oesophagus and the small
intestine.
- In the supine position, it is usually located in the
left upper quadrant, where it occupies parts of the epigastric,
umbilical, and left hypochondriac
regions.
- In most people, the stomach is J-shaped and its pyloric
part lies horizontally or ascends to the duodenum.
- The stomach is a very distensible organ. The empty stomach is only of slightly larger
calibre than the large intestine.
- It can, however, undergo considerable expansion and hold 2-3 litres of food.
Curvatures of the Stomach
The Lesser Curvature
- This is continuous with the right border of the oesophagus
and forms the concave border of the stomach.
- The angular notch (incisura angularis) is a sharp
angulation of the lesser curvature, which indicates the junction of the body and pyloric
parts of the stomach.
- This border is the attachment of the lesser
omentum.
The Greater Curvature
- This is continuous with the left border of oesophagus and
forms the convex border of the stomach.
- The greater curvature is 4 to 5 times longer than the lesser curvature.
- This border is the attachment of the greater
omentum and gastrosplenic ligament.
Parts of the Stomach
The Cardia
- This, with the cardiac orifice is situated to the left
of the midline behind the 7th costal cartilage,
2.5 cm from its sternal junction at the level of T11.
The Fundus
- This is a rounded vault to the left and superior to the cardiac orifice.
- The fundus is the most superior part of the stomach and is related to the left dome of the diaphragm.
- It is separated from the cardiac part by the cardiac notch or
incisure.
The Body of the Stomach
- This is the main portion of the stomach.
- It lies between the fundus and pyloric antrum.
The Pyloric Part of the
Stomach
- This consists of a wide portion, the pyloric antrum,
and a narrow portion, the pyloric canal.
- The pyloric canal (1 to 2 cm long) is continuous with
the markedly constricted part, the pylorus.
The Pylorus
- The pylorus of the stomach (G. gatekeeper) is the distal sphincteric region that guards
the pyloric orifice.
- Its wall is thicker because it contains extra circular smooth muscle.
- The pylorus is normally in tonic contraction.
- At irregular intervals, gastric peristalsis passes
chyme through the pyloric canal to the small intestine.
- The pyloric orifice lies about 1.2 cm to the right of the midline in the transpyloric plane (L1) when the stomach is empty and the
patient supine.
Relations of the Stomach
- The stomach is covered completely by peritoneum, except
where the blood vessels run along its curvatures, and a small bare
area posterior to the cardiac orifice.
The Anterosuperior
Surface
- Left costal margin
- Left diaphragm (6th to 9th intercostal
spaces)
- Gastric surface of the spleen
- Left and quadrate lobes of the liver
- Anterior abdominal wall
- Transverse colon (when the stomach is empty)
The Posteroinferior surface
(stomach bed)
- Superiorly: part of the diaphragm (left crus), the
spleen, the left suprarenal gland and upper pole of the left kidney.
- Inferiorly: body and tail of pancreas, transverse
mesocolon, left colic flexure and the splenic artery.
The Stomach Interior
- There are longitudinal mucosal folds called rugae and
run from high in the body to the pyloric antrum and canal.
Phases of Gastric
Secretion
- Cephalic: secretion in response to smell and taste of
food.
- Gastric: in response to the presence of food in the
stomach.
- Intestinal: gastric secretion and motility is decreased by impulses from the duodenum.
Arterial Supply to the Stomach
- The stomach has a rich blood supply from all three branches of the coeliac
trunk.
The Left Gastric Artery
- This is a small branch of the coeliac trunk.
- At the stomach, it runs from the cardiac part of the stomach
along the lesser curvature, frequently as two branches, to the pylorus.
- It sits between the layers of the lesser omentum
(hepatogastric ligament).
- It supplies both surfaces of the stomach and anastomoses with the right gastric artery.
The Right Gastric Artery
- This is a branch of the common hepatic artery.
The Left Gastro-omental
(Gastro-epiploic) Artery
- This is a branch of the splenic artery and runs along
the greater curvature of the stomach.
- This vessel runs between the layers of the greater
omentum, a short distance from its attachment to the stomach.
The Right Gastro-omental
(Gastro-epiploic) Artery
- This is a branch of the gastroduodenal artery.
- It runs towards the left and anastomoses with the left gastro-omental artery.
- It sends branches to the right part of the stomach and superior part of the duodenum.
The Short Gastric Arteries
- These are also branches of the splenic artery.
- There are usually 4-5 of these.
- They run between the layers of the gastrosplenic ligament
to the fundus of the stomach.
- They anastomose with the left gastric and left gastro-omental arteries.
Venous Drainage of
the Stomach
- The larger veins usually accompany the main arteries.
- The right gastro-omental vein drains into the superior mesenteric vein, and then into the portal
vein.
- The left gastro-omental vein drains into the splenic vein and then into the portal
vein.
- The left and right gastric veins drain into the portal vein directly.
Lymphatic Drainage
of the Stomach
- Gastric lymphatics are continuous at the pylorus with the duodenal lymphatics and the oesophageal lymphatics at the
cardia.
- Lymph channels largely follow the blood vessels and 4 main groups
have been identified.
- Right Gastro-omental group: the drains the greater curvature as far as the pylorus.
- These nodes drain into the pyloric nodes.
- All the nodes eventually drain into the coeliac nodes
and from there to the thoracic duct.
Nerve Supply of the
Stomach
Sympathetic Innervation
- This is from the greater and lesser splanchnic nerves
and left phrenic nerve to the coeliac
plexus.
- Then, it is through extensions of the coeliac plexus
along the gastric and gastro-omental arteries.
Parasympathetic
Innervation
- The anterior and posterior gastric nerves are usually derived from the left and right
vagus respectively.
The anterior vagal trunk gives rise to:
- Hepatic branches and pyloric branches.
- A fundal branch to the fundus.
- The anterior nerves of Latarjet.
The posterior vagal trunk gives rise to:
- Coeliac branches to the coeliac plexus around the coeliac trunk.
- The posterior nerves of Latarjet.
