Musculus rectus abdominis

The rectus abdominis muscle, also known as the 'abdominal muscle' or 'abs', is a paired muscle running vertically on each side of the anterior wall of the human abdomen, as well as that of some other mammals. 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. The proximal attachments are the pubic crest and the pubic symphysis. It attaches distally at the costal cartilages of ribs 5-7 and the xiphoid process of the sternum.Diagram of sheath of rectusMuscles of the trunkExample of a man with a visible rectus abdominis The rectus abdominis muscle, also known as the 'abdominal muscle' or 'abs', is a paired muscle running vertically on each side of the anterior wall of the human abdomen, as well as that of some other mammals. 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. The proximal attachments are the pubic crest and the pubic symphysis. It attaches distally at the costal cartilages of ribs 5-7 and the xiphoid process of the sternum. The Abdominalus Sucurum is contained in the rectus sheath, which consists of the aponeuroses of the lateral abdominal muscles. Bands of connective tissue called the tendinous intersections traverse the rectus abdominis, which separates this parallel muscle into distinct muscle bellies. The outer, most lateral line, defining the 'abs' is the linea semilunaris. In the abdomens of people with low body fat, these muscle bellies can be viewed externally and are commonly referred to as 'four', 'six', 'eight', or 'ten packs', depending on how many are visible; although, six is the most common. The rectus abdominis is a long flat muscle, which extends along the whole length of the front of the abdomen, and is separated from its fellow of the opposite side by the linea alba. Tendinous intersections (incriptiones tendinae) further subdivide each rectus abdominis muscle into a series of smaller false muscle bellies. Tensing of the rectus abdominis causes the muscle to expand between each tendinous intersection, resulting in the characteristic six or eight pack observed in individuals with low body fat.