Rectus abdominis m.

The rectus abdominis muscle, also known as the "abs and lower abdominals," is a paired muscle running vertically on each side of the anterior wall of the abdomen. There are two parallel muscles, separated by a midline band of connective tissue called the linea alba. It extends from the pubic symphysis, pubic crest and pubic tubercle inferiorly, to the xiphoid process and costal cartilages of ribs V to VII superiorly.

It is contained in the rectus sheath, which consists of the aponeuroses of the lateral abdominal muscles.

Three bands of connective tissue called the tendinous intersections traverse the rectus abdominus, which separates this parallel muscle into eight distinct muscle bellies. In the abdominal region of well conditioned athletes, the three superior bellies on the left and right side of the umbilicus can be easily viewed externally resulting in the rectus abdominus being commonly referred to as the "six-pack."