The illustration shows both external abdominal muscles. Depicted are the abdominal external oblique muscle (lateral), the rectus abdominis muscles (medial) and the serratus anterior muscle (cranio-dorsal), with the last one not being part of the abdominal muscles. Covered are the abdominal internal oblique muscle, the transversus abdominis muscle and the pyramidalis muscle. The abdominal muscles have many functions, e.g. bending and turning of the trunk, holding the body in an upright position and exspiration. In athletes the abdominal muscles often show as a six-pack. The base for that is hypertrophy of the rectus abdominis muscle as well as reduction of subcutaneous fat.