The Stomach

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.

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Parts of the Stomach

• For the purposes of description, the stomach is divided into five parts: a cardiac part, fundus, body, pyloric part and pylorus.

The Cardia

• This, with the cardiac orifice is situated to the left of the midline behind the 7^th 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.

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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 two layers of lesser omentum surround the stomach, and leave its greater curvature as the greater omentum.

The Anterosuperior Surface

• Left costal margin
• Left diaphragm (6^th to 9^th 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)

• The bed of the stomach is formed by the posterior wall of the omental bursa, and retroperitoneal structures between it and the posterior abdominal wall.

• 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

1. Cephalic: secretion in response to smell and taste of food.
2. Gastric: in response to the presence of food in the stomach.
3. Intestinal: gastric secretion and motility is decreased by impulses from the duodenum.

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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.

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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.

• Gastric group: this drains the region supplied by the left gastric artery.

• Pancreaticolienal group: the drains the gastric fundus and body left of a vertical line drawn from the oesophagus.

• Right Gastro-omental group: the drains the greater curvature as far as the pylorus.
• These nodes drain into the pyloric nodes.

• Right Gastric and Pyloric nodes: drains the pyloric part of the stomach.

• 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:

1. Hepatic branches and pyloric branches.
2. A fundal branch to the fundus.
3. The anterior nerves of Latarjet.

The posterior vagal trunk gives rise to:

1. Coeliac branches to the coeliac plexus around the coeliac trunk.
2. The posterior nerves of Latarjet.

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