Overview
This lecture covers the anatomy, features, blood supply, nerve supply, histology, functions, and clinical relevance of the stomach.
Structure and Location of the Stomach
- The stomach is a muscular bag, the widest part of the digestive tube, between the esophagus and duodenum.
- Acts as a food reservoir and aids digestion of carbohydrates, proteins, and fats.
- Located in the epigastric, umbilical, and left hypochondriac regions of the abdomen, under the left costal margin and ribs.
- Shape varies: J-shaped in thin/tall people, more horizontal in broad/active people.
- Measures about 25 cm long; capacity is 30 mL at birth, 1 L at puberty, and 1.5–2 L in adults.
External Features
- Two orifices: cardiac (esophagus joins, T11 level) and pyloric (opens to duodenum, L1 level).
- Two curvatures: lesser (right border, concave, attaches lesser omentum) and greater (left border, convex, attaches greater omentum, 5x longer).
- Two surfaces: anterior (faces forward/up), posterior (faces backward/down).
- Two main parts: cardiac (fundus and body) and pyloric (pyloric antrum and canal).
Internal Structure and Layers
- Four layers: mucosa (with gastric rugae and pits), submucosa (connective tissue, vessels, nerves), muscle coat (longitudinal, circular, oblique fibers), and serosa (peritoneum).
- Gastric glands (in fundus/body) have mucous, chief (digestive enzyme), and parietal (HCl) cells.
Peritoneal and Visceral Relations
- Stomach is lined by peritoneum on both surfaces.
- Lesser curvature connects to lesser omentum; greater curvature to greater omentum, gastro-splenic, and gastro-phrenic ligaments.
- Anteriorly related to liver, diaphragm, transverse colon, and abdominal wall.
- Posteriorly related to diaphragm, left kidney, left suprarenal gland, pancreas, transverse mesocolon, splenic flexure, splenic artery (separated by lesser sac).
Blood and Lymphatic Supply
- Blood supply: left/right gastric, left/right gastroepiploic, short gastric, splenic, and gastroduodenal arteries.
- Lesser curvature: left/right gastric arteries; greater curvature: left/right gastroepiploic arteries; fundus: short gastric arteries.
- Venous drainage: portal, superior mesenteric, and splenic veins.
- Lymphatic drainage divided into four zones (pancreatico-splenic, left gastric, right gastroepiploic, pyloric/hepatic nodes).
Nerve Supply
- Sympathetic (vasomotor, sensation, motor to pyloric sphincter) and parasympathetic (anterior/posterior gastric nerves) innervation.
Functions
- Food reservoir, mixes and softens food through peristalsis.
- Secretes gastric juice (digestive enzymes, HCl, intrinsic factor for vitamin B12 absorption).
- Absorbs small amounts of alcohol, water, salts, and drugs.
Clinical Anatomy
- Peptic/gastric ulcers commonly occur along the lesser curvature.
- Gastric carcinoma is frequent along the greater curvature.
- Pyloric obstruction may be congenital or acquired.
- Hypotonic stomach increases risk for gastric ulcers.
Histology
- Cardiac region: simple columnar epithelium with small tubular glands.
- Fundus and body: straight simple tubular gastric glands.
- Pyloric part: pyloric glands.
Key Terms & Definitions
- Cardiac Orifice — Opening where the esophagus joins the stomach.
- Pyloric Orifice — Opening from stomach into duodenum.
- Lesser Omentum — Peritoneal fold from lesser curvature to liver.
- Greater Omentum — Large peritoneal fold hanging from greater curvature.
- Gastric Rugae — Folds in the stomach mucosa.
- Parietal Cells — Stomach cells secreting hydrochloric acid.
- Intrinsic Factor — Protein necessary for vitamin B12 absorption.
Action Items / Next Steps
- Review lecture notes and diagrams of stomach anatomy.
- Memorize blood vessels, nerve supply, and lymphatic drainage of the stomach.
- Prepare for questions on clinical conditions related to the stomach.