[NA] The part of the trunk that lies between the thorax and the pelvis. The abdomen does not include the vertebral regionposteriorly but is considered by some anatomists to include the pelvis (abdominopelvic cavity). It includes the greater partof the abdominal cavity, and is divided by arbitrary planes into nine regions. It is divided into nine regions by four imaginarylines projected onto the anterior wall; two of the lines pass horizontally around the body (the upper at the level of thecartilages of the ninth ribs, the lower at the tops of the crests of the ilia), and two extend vertically on each side of the bodfrom the cartilage of the eighth rib to the center of the inguinal ligament. The regions are: three upper-right hypochondriac,epigastric, left hypochondriac; three middle-right lateral, umbilical, left lateral; and three lower-right inguinal, pubic, leftinguinal. Syn: venter, belly.