Stomach

At a glance

English

Stomach

Latin (TA2)

Gaster

System

Digestive

Region

Abdomen

Side

Single, on the midline

About the stomach

Of the whole digestive tube, the stomach is the widest part. It lies mainly in the left upper quadrant and epigastrium, under the left dome of the diaphragm, partly protected by the lower left ribs. Its shape and position change a great deal with posture, body build and how full it is: an empty stomach is a narrow tube, a full one may hold well over a litre. It receives food from the oesophagus at the cardia and passes it on to the duodenum through the pylorus, roughly opposite vertebra L1.

It has two openings, two curvatures, two walls and several regions. The short concave lesser curvature forms the right border and the long convex greater curvature the left and lower border. From the cardia the dome-shaped fundus rises to the left; the large body forms the middle, and the pyloric part, beginning at the angular incisure, includes the antrum, the canal and the thick pyloric sphincter. The lesser omentum hangs from the lesser curvature to the liver and the greater omentum from the greater curvature. In front are the liver, diaphragm and front abdominal wall. Behind lies the lesser sac, and behind that the stomach bed: the pancreas, left kidney and adrenal gland, spleen, splenic artery and transverse mesocolon.

The muscle coat has three layers, adding an inner oblique layer to the usual circular and longitudinal ones, and this lets the stomach churn food into a semi-liquid chyme. Its glands secrete hydrochloric acid, which destroys many swallowed microbes and activates pepsin for protein digestion, along with intrinsic factor, needed to absorb vitamin B12. The pyloric sphincter releases chyme to the duodenum in small portions.

Common problems include gastritis and peptic ulcers, often linked to Helicobacter pylori or anti-inflammatory drugs; an ulcer of the back wall can erode the splenic artery or penetrate the pancreas. Part of the stomach may slip through the diaphragm as a hiatus hernia. In infants, overgrowth of the pyloric muscle (pyloric stenosis) causes forceful vomiting. Stomach cancer often arises near the lesser curvature and antrum.

Function and supply

Function

Stores swallowed food, mixes it with acid and enzymes into chyme, starts protein digestion and releases chyme gradually into the duodenum.

Nerve supply

Anterior and posterior vagal trunks increase secretion and movement; sympathetic fibres from the coeliac plexus (greater splanchnic nerves) carry pain and reduce activity.

Blood supply

Branches of the coeliac trunk: left and right gastric arteries along the lesser curvature, right and left gastro-omental arteries along the greater curvature, and short gastric arteries to the fundus.