The anatomy of the regions and planes of the abdomen is composed of many layers with varying blood supply and innervation. The abdomen has been bisected, trisected, and even divided into as many as 9 separate regions. The layers of the abdominal wall consist of the skin, superficial fascia, and muscles.
The anatomic planes of the abdominal wall are made up of multiple muscular and fascial layers that interdigitate and unite to form a sturdy, protective musculofascial layer that protects the visceral organs and provides strength and stability to the body’s trunk. This anatomy varies with respect to the different topographic regions of the abdomen; thus, a firm understanding of these layers, their blood supply, and their innervation is essential to surgical management of the abdomen.
The abdominal cavity is the largest hollow space in the body. It is bound cranially by the xiphoid process of the sternum and the costal cartilages of ribs 7-10; caudally, by the anterior ilium and the pubic bone of the pelvis; anteriorly, by the abdominal wall musculature; and posteriorly, by the L1-L5 vertebrae.
The abdominal wall has few anatomic landmarks. The flat abdominal plane is broken up only by the costal margins, anterior superior iliac spines, and the umbilicus. Thus, many attempts have been made over the years to describe what surface anatomy cannot.
The most common and widely accepted system for identification of the various regions of the abdomen is the simple division of the abdomen into 4 quadrants by a vertical and horizontal line bisecting the umbilicus and forming the right and left upper and lower quadrants (see the image below).
Division of the abdomen into 4 quadrants.