- Stomach is the most dilatable part of alimentary tract intervening between esophagus and duodenum. It occupies epigastric, umbilical and left hypochondriac regions. When empty, it is J-shaped, and when partially distended, it becomes pyriform in shape. The mean capacity of stomach is 30 ml (one ounce) at birth, 100 ml at puberty and 1.5 - 2 liters in adults.
- Stomach has two orifices (proximal cardiac orifice and distal pyloric orifice), two curvatures (lesser curvature and greater curvature) and two surfaces (anterior/anterosuperior and posterior/posteroinferior). The most dependent part of lesser curvature is marked by angular notch (incisura angularis).
- The stomach is divided into two parts by line drawn downwards and to the left from incisura angularis :
- Cardiac part: It is divided into upper convex dome shaped 'fundus' and body of the stomach.
- Pyloric part: Is divided into pyloric antrum and pyloric canal.
The posterior surface of stomach is related to structures forming the stomach bed, all of which are separated from stomach by the cavity of the lesser sac. These structures forming stomach bed are (i) Diaphragm, (ii) left kidney, (iii) left suprarenal (adrenal) gland, (iv) pancreas (body), (v) transverse colon, (vi) splenic flexure of colon and (vii) splenic artery. Sometimes spleen is also included in stomach bed, but it is separated from stomach by greater sac (not lesser sac).
Arterial supply of stomach is as follows -
- Along lesser curvature: Left gastric artery (branch of coeliac trunk and right gastric artery (branch of proper hepatic artery.
- Along greater curvature: Right gastroepiploic artery (branch of gastroduodenal artery) and left gastroepiploic artery (branch of splenic artery).
- Fundus: 5-7 short gastric arteries (branches of splenic artery)
- The veins of stomach drain into the portal, superior mesenteric and splenic veins: -
- Right gastric vein and left gastric vein drain into portal vein.
- Short gastric vein and left gastroepiploic vein drain into splenic vein.
- Right gastroepiploic vein drains into superior mesenteric vein.
- Lymphatic drainage of stomach is divided into 4 sectors:
- Upper part of left 1/3rd of body along greater curvature and fundus drain into pancreaticosplenic nodes.
- Body of stomach along lesser curvature drains into left gastric nodes (superior gastric nodes).
- Lower part of body close to greater curvature and pyloric antrum drain into right gastroepiploic (inferior gastric) nodes which in turn drains into subpyloric (pyloric) nodes.
- Pyloric canal drains into pyloric (subpyloric) nodes, hepatic nodes and left gastric nodes.
- Finally all lymphatics from these nodes drain into coeliac group of lymph nodes.
- The stomach is supplied by sympathetic and parasympathetic system. The sympathetic nerves are derived from T6-T9 spinal nerve segments via greater splanchnic nerves, and coeliac and hepatic plexus. Pain sensations from stomach are carried along sympathetic fibers. The parasympathetic nerves are derived from right vagus and left vagus which enter the abdomen as anterior vagal trunk (anterior gastric nerve) from left vagus and posterior vagal trunk (posterior gastric nerve) from right vagus.
- Anterior vagal trunk gives:
- Main gastric nerve of Laterjet,
- Pyloric branch and
- Hepatic branch.
- Posterior vagal trunk gives:
- Nerve of Grassi to fundus,
- Coeliac branches, and
- Main gastric nerve of Laterjet.