The illustration shows both abdominal muscles. The abdominal external oblique muscle (lateral), the rectus abdominis muscle (medial) and the serratus anterior muscle (cranio-dorsal) are shown whereas latter does not count as an abdominal muscle. The abdominal internal oblique muscle, the abdominal transversal muscle and the pyramidalis muscle are covered. The abdominal musculature has several functions such as flexion and rotation of the torso, maintaining posture and expiration. Ahtletes often have a so-called six-pack. Hypertrophy of the rectus abdominis muscle is the foundation of this as well as decreased fatty tissue in the subcutis.