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The Stomach - Anatomy

The stomach is a J-shaped, distensible dilation of the alimentary canal, interposed between the esophagus proximally and the duodenum distally. Its volume ranges from ~30 mL in a neonate to 1.5-2 L in the adult.

1. Position and Relations

The stomach lies in the left hypochondriac and epigastric regions of the abdomen:

The esophagogastric junction sits to the left of the T10 vertebral body, 1-2 cm below the diaphragmatic hiatus
The gastroduodenal junction lies at L1, generally right of midline

Anterior relations: liver, anterior abdominal wall Posterior relations (forming the "stomach bed"): pancreas, transverse colon, diaphragm, spleen, left kidney and adrenal gland. The posterior gastric wall forms the anterior wall of the omental bursa (lesser sac).

2. Gross Anatomy - Parts

Anatomical regions of the stomach showing fundus, body, antrum, pylorus, and the two mucosal zones

The stomach has 4 anatomical regions:

Region	Description
Cardia	Small area immediately at the esophagogastric junction
Fundus	Dome-shaped superior portion, lies above the cardia, contacts the left hemidiaphragm and spleen
Body (Corpus)	Largest part, extends from fundus to the incisura angularis
Antrum + Pylorus	Distal region ending at the pyloric sphincter; the pylorus joins the duodenum at L1

The incisura angularis is a fixed, sharp indentation two-thirds down the lesser curvature - it marks the caudal boundary of the body.

Curvatures:

Lesser curvature - right upper border, shorter
Greater curvature - left lower border, longer; may extend below the umbilicus when distended

3. Peritoneal Attachments (Ligaments)

The stomach is almost completely covered by peritoneum. This peritoneum extends as:

Ligament	From - To
Lesser omentum (gastrohepatic part)	Lesser curvature → liver
Greater omentum / Gastrocolic ligament	Greater curvature → transverse colon
Gastrosplenic ligament	Greater curvature → spleen
Gastrophrenic ligament	Fundus → diaphragm

4. Blood Supply

Arterial blood supply of the stomach showing the two anastomotic arcades on lesser and greater curvatures

All arterial supply derives from the celiac trunk via three branches:

Lesser curvature arcade:

Left gastric artery (direct celiac branch) - from above
Right gastric artery (from common hepatic artery) - from below

Greater curvature arcade:

Left gastroepiploic artery (from splenic artery) - from above/left
Right gastroepiploic artery (from gastroduodenal artery) - from below/right

Fundus:

Short gastric arteries (vasa brevia) - from the terminal splenic artery

The gastroduodenal artery passes behind the first part of the duodenum - clinically important because a posterior duodenal ulcer can erode it causing severe bleeding.

Venous drainage: Mirrors the arteries, all draining ultimately into the portal vein (or its tributaries - splenic and superior mesenteric veins). The left gastric (coronary) vein becomes dilated in portal hypertension, forming oesophageal varices.

5. Lymphatic Drainage

Most gastric lymph drains ultimately to the celiac nodes via 4 intermediate groups:

Inferior gastric → subpyloric/omental → hepatic → celiac
Splenic/superior greater curvature → pancreaticosplenic → celiac
Superior gastric/lesser curvature → left & right gastric nodes → celiac
Hepatic/pyloric → suprapyloric → hepatic → celiac

Lymphatics anastomose freely within the gastric wall - this explains why gastric cancer can spread widely before detection.

6. Nerve Supply

Parasympathetic (vagus nerve):

Left and right vagus nerves form the anterior and posterior vagal trunks at the cardia
Each trunk gives celiac and hepatic branches, then continues as the anterior and posterior nerves of Latarjet (running in the lesser omentum)
These give multiple gastric branches and end as the "crow's foot" at the antrum
Due to the 90° embryological rotation: left vagus = anterior trunk; right vagus = posterior trunk

Sympathetic:

Preganglionic fibers from T6-T8, synapsing in the celiac ganglia
Postganglionic fibers travel with blood vessels
Carry afferent pain fibers and motor fibers to the pyloric sphincter

7. Histology - Wall Layers

The stomach wall has the standard GI layers (mucosa, submucosa, muscularis propria, serosa) with some specializations:

Muscularis propria has 3 layers (unlike the rest of the GI tract which has 2):

Outer longitudinal
Middle circular
Inner oblique (unique to stomach - helps churning)

The pyloric sphincter is a thickening of the circular muscle layer.

8. Microscopic Anatomy - Gastric Mucosa

Histological appearance of a gastric gland showing mucus cells at surface, eosinophilic parietal cells superficially, and basophilic chief cells at the base

The entire mucosa is lined by columnar epithelium with numerous gastric pits (crypts) - tubular invaginations each opening into 4-5 gastric glands.

Three types of gastric glands:

Cardiac glands

Adjacent to the esophagogastric junction
Contain mucous, endocrine, and undifferentiated cells
No parietal or chief cells

Oxyntic (parietal) glands - Body & Fundus (75-80% of stomach)

Contain three specialized cell types:

Cell	Location in gland	Secretion	Function
Parietal cells	Upper/mid gland	HCl + Intrinsic Factor	Acid secretion via H⁺/K⁺-ATPase; essential for B12 absorption
Chief cells	Deepest part	Pepsinogen I & II	Protein digestion (activated to pepsin by acid)
Surface mucous cells	Mucosal surface	Mucus	Protective barrier

Pyloric glands - Antrum (15-25% of stomach)

Contain G cells (secrete gastrin - stimulates acid)
D cells (secrete somatostatin - inhibits acid)

ECL cells (enterochromaffin-like) are distributed throughout the body and produce histamine, a key driver of parietal cell acid secretion.

9. Functional Areas Summary

Functional Zone	Anatomical Region	Key Cells/Function
Oxyntic gland area	Cardia, Fundus, Body	Parietal cells (HCl), Chief cells (pepsinogen)
Pyloric gland area	Antrum + Pylorus	G cells (gastrin), antral pump for gastric emptying

10. Embryology (Brief)

The stomach is recognizable at week 4 as a dilation of the distal foregut. It rotates 90° around its longitudinal axis, which explains:

Greater curvature points left (was dorsal)
Lesser curvature points right (was ventral)
Left vagus innervates the anterior wall; right vagus innervates the posterior wall

Sources: Sleisenger & Fordtran's Gastrointestinal and Liver Disease, Ch. 49 | Bailey & Love's Short Practice of Surgery, 28th ed., Ch. 67 | Yamada's Textbook of Gastroenterology, 7th ed., Ch. 17

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