This document provides an overview of the anatomy of the abdomen, including surface anatomy, abdominal quadrants, muscles of the anterior and posterior abdominal walls, the abdominopelvic cavity, peritoneum, divisions of the peritoneal cavity, and blood supply. Key points include: the abdomen is divided into 9 regions within 4 quadrants; the anterior abdominal wall muscles include the rectus abdominis, internal and external obliques, and transversus abdominis; the peritoneum lines the abdominal cavity and organs; and the peritoneal cavity is divided into supracolic, infracolic, and pelvic compartments.