Rectus abdominis is one of the muscles of the anterior abdominal wall. It is divided into two parts which abut each other either side of the linea alba.
It originates from the symphysis pubis and the pubic crest. From here it passes superiorly, broadening in the process, to insert into the anterior surface of the xiphoid process, the medial part of the costal margin and the 5th to 7th costal cartilages.
Rectus abdominis is enclosed within the rectus sheath. The rectus sheath is strongly adherent to the muscle at three of four tendinous intersections.
The actions of rectus abdominis are manifold:
- flexion of the trunk on the pelvis
- elevation of intra-abdominal pressure eg. during parturition, 'abdominal breathing'
- stabilization of the pelvis to permit the lower limb muscles to work more effectively
Rectus abdominis is innervated by the anterior primary rami of the inferior intercostal and subcostal nerves (T7-12).