In front and at the sides it is bounded by the lower ribs and abdominal muscles.
Behind by the vertebral column and muscles.
Regions.—For convenience of description of the viscera, the abdomen is artificially divided into nine regions. Thus if two circular lines are drawn around the body, the one at the extremities of the ninth ribs where they join the costal cartilages, and the other around the crest of the ileum, the abdominal cavity is divided into three zones.
Fig. 22—The regions of the abdomen and their contents. (Gray)
If two parallel lines are now drawn perpendicular upward from the center of Poupart's ligament, each of these zones is subdivided into three parts.
The middle region of the upper zone is called the epigastric; and the two lateral regions, the right and left hypochondriac. The central region of the middle zone is called the umbilical; and the two lateral regions, the right and left lumbar regions. The middle region of the lower zone is called the hypogastric; and the two lateral regions are called the right and the left inguinal regions.
The viscera contained in each of these are as follows:
| Right Hypochondriac | Epigastric Region | Left Hypochondriac |
| The greater part of the right lobe of the liver, the hepatic flexure of the colon and part of the right kidney. | The greater part of the stomach including both cardiac and pyloric orifices, the left lobe and part of the right lobe of the liver and the gall-bladder, the pancreas, the duodenum, the suprarenal capsules and parts of the kidneys. | The fundus of the stomach, the spleen, the extremity of the pancreas, the splenic flexure of the colon and part of the left kidney and small portion of the left lobe of the liver. |
| Right Lumbar | Umbilical Region | Left Lumbar |
| Ascending colon, part of the right kidney and some convolutions of the small intestines. | The transverse colon, part of the great omentum and mesentery, transverse part of the duodenum and some convolutions of the jejunum and ileum and part of both kidneys. | Descending colon, part of the omentum, part of the left kidney and some convolutions of the small intestines. |
| Right Inguinal or Iliac | Hypogastric Region | Left Inguinal or Iliac |
| The caecum and vermiform appendix and a portion of the ascending colon. | Convolutions of the small intestines, the bladder in children and in adults if distended, and the uterus during pregnancy. | Sigmoid flexure of the colon and a portion of the descending colon. |