The abdominal cavity is a single cavity that houses two hollow tubular systems:

Figure 3-1
Four quadrants of the abdominal area divided by the median plane vertically and transumbilical plane horizontally.

• gastro-intestinal
• uro-genital.

The abdominal cavity extends from the diaphragm to the floor of the pelvis. One can further subdivide this cavity into an abdomen proper, and pelvis.

The abdomen proper extends from the diaphragm superiorly to a plane connecting the two superior edges of the ilium inferiorly. The pelvis begins superiorly at this plane and extends inferiorly to the floor of the pelvis or the pelvic diaphragm.

Generally speaking, the gastro-intestinal system and its organs are found in the abdomen proper; the uro-genital system and its associated organs are located in the pelvis. There is, however, some overlap of each organ system into the space of the other.

For descriptive purposes, the abdominal area is divided into four quadrants: (Figure 3-1)

• upper right
• upper left
• lower right
• lower left