The regions of abdomen are the different parts into which the human venter (belly) is anatomically divided. The upper part of abdomen has an epigastric region (epigastrium), which is triangular, and two, left and right, hypochondriac regions. In the middle portion of the belly, two lateral abdominal, right and left, regions, and a middle umbilical region. The lower part of the abdomen, called hypogastrium, also has two lateral regions, which are called the inguinal regions (right and left), and a middle pubic region.
Right and left costal arches are clearly outlined when the abdominal wall is pulled in. The xiphoid process is left in the angle formed by the cartilaginous costal arches, which is called infrasternal angle. The inguinal folds that correspond to the position of the inguinal ligaments are distinctively seen in the lower portion of abdominal wall. When the abdominal muscles are tensed, a groove get formed running vertically along the midline; it is the linea alba abdominis. The umbilicus lies right in the middle of the linea alba, on the level of the articulation between the third and fourth lumbar vertebrae.
The rectus abdominis muscles are outlined to both sides of the midline. The tendinous intersection of these muscles are defined clearly as three or four transverse constrictions. The slips of the external oblique muscle alternating with slips of serratus anterior and longissimus dorsi muscle are outlined on the upper part of the anterolateral portion of thoracic wall.
Below, you can see a schematic drawing of the regions of abdomen and the thorax.
