abdomenstomach

The abdomen is the large body cavity between the diaphragm and the pelvis that houses most of the digestive organs, including the stomach. The stomach is a J-shaped organ within the upper abdomen that acts as a temporary reservoir and mixing chamber for ingested food as part of the digestive system.

Anatomy and positioning: The stomach lies mainly in the upper left portion of the abdomen and is intraperitoneal, connected to the esophagus at the cardia and to the small intestine at the pylorus. Its external surface features the greater and lesser curvatures, and its internal regions are the cardia, fundus, body, and antrum. The stomach is suspended by folds of peritoneum, including the greater and lesser omenta, which connect it to other organs and help organize the abdominal contents.

Function: The stomach performs mechanical digestion through rhythmic muscular contractions that churn and mix contents. Chemical digestion begins with gastric acid (hydrochloric acid) and digestive enzymes such as pepsin, produced by gastric glands. The mucous lining protects the stomach from acid and microbes. The stomach also secretes intrinsic factor, essential for vitamin B12 absorption in the small intestine, and regulates emptying into the duodenum via the pyloric sphincter.

Circulation, innervation, and lymph: Blood supply mainly comes from branches of the celiac trunk, including the left gastric, right gastric, left gastroepiploic, and right gastroepiploic arteries. Venous drainage routes chiefly to the portal system. Parasympathetic input is via the vagus nerves, while sympathetic fibers arise from thoracic splanchnic nerves; lymphatics drain to celiac lymph nodes.

Clinical notes: Common conditions affecting the stomach include gastritis, peptic ulcer disease, gastroesophageal reflux disease, and stomach cancer. Evaluation often uses endoscopy and imaging, with treatment guided by etiology and may involve medication, lifestyle changes, or surgical intervention in some cases.