ASGE Recognized Industry Associate (ARIA) Training Program OPEN | October 2025-GI Tract in Health_Esophagus

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The gastrointestinal (GI) tract comprises a series of digestive organs including the esophagus, stomach, liver, gallbladder, pancreas, small intestine, and large intestine. Its primary function is digestion—the breakdown of food into smaller components—enabling absorption of nutrients and minerals necessary for growth, metabolism, maintenance, and reproduction.<br /><br />Digestion involves mechanical and chemical processes. Mechanically, mastication (chewing), peristalsis (wave-like muscle contractions propelling food), and segmentation (mixing movements) occur. Chemically, digestion is facilitated by saliva, gastric acid, pancreatic enzymes, and bile.<br /><br />The digestive process involves three main steps: motility (movement of food through muscular contractions), secretion (release of acids and enzymes), and absorption (nutrients and water absorbed into the bloodstream).<br /><br />Starting in the mouth, food is chewed and mixed with saliva—produced by parotid, submandibular, and sublingual glands—which moistens food, initiates carbohydrate digestion via amylase, and provides antibacterial effects. The esophagus, a hollow muscular tube about 18-26 cm long, transports the food bolus to the stomach. Its walls consist of several layers including mucosa (lined by stratified squamous epithelium), and muscles that include an inner circular and outer longitudinal layer. The upper third contains voluntary skeletal muscle, while the lower esophagus has involuntary smooth muscle. The lower esophageal sphincter at the gastroesophageal junction prevents acid reflux by relaxing during swallowing and contracting otherwise.<br /><br />The stomach is a J-shaped reservoir where food is mixed with acid and enzymes; partially digested food moves gradually into the small intestine. It has distinct parts (fundus, body, antrum, pylorus) and features mucosal folds called rugae. Its wall comprises multiple layers from surface epithelium through various muscle layers (longitudinal, circular, oblique) to serosa. Specialized gastric cells (parietal, chief, enteroendocrine) produce acid, enzymes, and hormones that regulate digestion.<br /><br />Understanding basic GI anatomy and physiology is crucial for grasping digestive health and disease mechanisms.

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Kajali Mishra, MD

Keywords

gastrointestinal tract

digestion

esophagus

stomach

small intestine

large intestine

digestive enzymes

peristalsis

absorption

gastric acid