The abdominal muscles are located on the front of the body between the ribs and the pelvis, explains the Better Health Channel. The abdominal muscles are composed of four main muscle groups, which support the trunk, and allow movement, while holding the abdominal organs in place.
The four main abdominal muscle groups are the transversus abdominus, rectus adbominus, external oblique muscles and internal oblique muscles.
The tranversus adbominus muscle layer is the deepest of the four and acts to stabilize the trunk and maintain internal pressure of the abdominal cavity.
The rectus abdominus, or "six pack" region, is a long, flat muscle that runs the entire length of the abdomen between the ribs and the pelvic bone.
The external oblique muscles are on each side of the rectus abdominus and are responsible for twisting the trunk of the body. The internal oblique muscles are also on each side of the abdomen, resting between the transverse abdominus and external obliques.