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The Stomach


Surgical Anatomy:
Stomach is the muscular organ, which is the dilated part of the alimentary canal. It has three main functions:
  • Storage of food – 1500ml
  • Mixes the food wit gastric secretions to form semi fluid, CHYME.
  • Controls the rate of delivery of chyme to the small intestine
It is roughly J- shaped and has two openings (the cardiac and the pyloric orifices), two curvatures (Greater and lesser) and two surfaces (anterior and posterior). It has fundus, which is dome-shaped that is projected upward and to the left of the cardiac orifices. It is usually full of gases. The body extends from the end of the cardiac orifice to level of the “incissura angularis” (which is the constant notch in the lower part of the lesser curvature). Pyloric antrum extends from the incissura angularis to the Pylorus. Pylorus is the tubular part of the stomach and has a thick muscular wall called pyloric sphincter. The lesser curvature forms the right border of the stomach and extends from the cardiac orifice to the pylorus. The greater curvature is much larger than the lesser curvature and extends from the left of the cardiac orifice and forms the left border to the pylorus. The cardiac orifice is where the abdominal part of esophagus enters the stomach. The pyloric orifice is formed by the pyloric canal, which is 2.5cm long. The circular muscle coat is much more thicker here and forms the anatomical and physiological pyloric sphincter.

The mucous membrane of the stomach is thick and has numerous folds that are mainly longitudinal in direction. The muscular wall of the stomach contains:
  • Longitudinal fibers, which are most superficial
  • Inner circular fibers, which encircle the body of stomach and are greatly thickened at the pylorus to form the pyloric sphincter
  • The oblique fibers from the innermost muscle coat.
Relations:
Anteriorly:
Anterior abdominal wall, left costal margin, left pleura and lungs, diaphragm, left lobe of liver.

Poteriorly:
Lesser sac, diaphragm, spleen, left supra-renal glands, upper part of the left kidney, splenic artery, pancreas, transverse mesocolon and transverse colon

Blood supply:
Left gastric artery: arises from celiac artery. It passes upwards and to the left to reach the esophagus and then descends along the lesser curvature. It supplies lower third of esophagus and upper right part of stomach.

Right gastric artery: arises from hepatic artery at the upper border of pylorus and runs to the left along lesser curvature. It supplies lower right part.

Short gastric arteries: arise from splenic artery, passes through the gastrosplenic ligament to supply the fundus

Left gastroepiploic artery: arises from splenic artery, passes forward into gastrosplenic omentum to supply the stomach along the upper part of the greater curvature.

Right gastroepiploic artery: arises from gastroduodenal branch of the hepatic artery. It passes to the left and supplies the stomach along the lower part of the greater curvature.

Venous drainage:
The veins drain into the portal circulation of liver. The left and the right gastric veins drain directly into the portal vein. The short gastric vein and the left gastroepiploic vein join the splenic veins. The right gastroepiploic vein joins the superior mesenteric vein.

Lymph drainage:
It follows the arteries in four groups:
  1. Those that drain into the lymph nodes along the left gastric vessels, then passes to celiac nodes.
  2. Those that drain into lymph nodes along the right gastric vessels, then into celiac nodes
  3. Those that drain into nodes along the short gastric arteries and left gastroepiploic artery and then drain into the lymph nodes at the Hylum of the spleen and into celiac nodes.
  4. Those that drain into lymph nodes along the right gastroepiploic artery and then into celiac nodes.
Nerve Supply:
The nerve supply comes from the celiac plexus and from the right & left vagus nerve. The anterior vagal trunk, which is formed in the thorax mainly from the left vagus nerve enter the abdomen on the anterior surface of the esophagus, the trunk divides into branches that supply the anterior surface of stomach. A large Hepatic branch passes up to the liver, and from this a pyloric branch passes down to the pylorus.

The posterior vagal trunk, which is formed in the thorax mainly from the right vagus nerve, enters the abdomen from posterior surface of the esophagus and divides into the branches to supply the posterior surface of the stomach (a celiac branch also arises from the posterior vagal trunk). The celiac sympathetic plexus carries a proportion of pain transmitting nerve fibers.

Increased secretion of the acid and pepsin is stimulated by the vagus nerve.

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This article has been written by Dr. M. Javed Abbas.
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21:00 21/12/2002