Topic overview

Start with the big picture

The gastrointestinal tract has four recurring wall layers: mucosa, submucosa, muscularis externa, and serosa or adventitia. Along its course, distinct structures support different roles: the mouth and pharynx receive and move a bolus, the esophagus carries it to the stomach, and the small and large intestines continue its passage. Key anatomical landmarks include the duodenal parts and duodenojejunal flexure, the contrasting features of jejunum and ileum, the ileocecal region, colonic flexures, and the pectinate line. The topic also introduces foregut, midgut, and hindgut arterial territories, peritoneal relationships, and the internal and external anal sphincters. Together, these features provide a framework for locating structures and understanding how anatomy relates to movement, drainage, and continence.