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Origin, insertion, innervation and function of the rectus abdominis muscle.
Hello again everyone! It’s Matt from Kenhub, and in this tutorial, we will discuss the rectus abdominis. The rectus abdominis muscle is a vertically running muscle of the anterior abdominal muscle group. The anterior abdominal muscles are part of the abdominal wall musculature. They tense the anterior abdominal wall together with the lateral abdominal muscles. The anterior abdominal muscles consist of the rectus abdominis muscle and the pyramidalis muscle.
As mentioned, the focus of this video is the rectus abdominis muscle. The rectus abdominis originates at the pubis, between the pubic tubercle and symphysis, and inserts on the 5th to 7th costal cartilages the xiphoid process of the sternum. It passes through the rectus sheath, a tendinous muscle envelope built by the aponeurosis of the lateral abdominal muscles.
It has 3-4 horizontal tendinous intersections which are adhered to the anterior layer of the rectus sheath giving it its multi-bellied appearance, although anyone with a 6-pack or washboard abs would probably not appreciate the term multi-bellied. These are traces of the segmental arrangement during embryogenesis or also known as metamerism.
The innervation of this muscle is provided by the 7th to 12th intercostal nerves. The main tasks of the rectus abdominis muscle is the movement of the trunk, stabilization of the vertebral column and the tensioning of the abdominal wall. They are responsible for the abdominal press increasing the intra-abdominal pressure which occurs during defecation or vomiting. Furthermore, they support exhalation by pulling down the thorax through their contraction. In particular, the contraction of the rectus abdominis muscle results in ventral or forward flexion, a flexion of the trunk, elevation of the pelvis, and lowering the thorax and thus is an important antagonist of the intrinsic back muscles.
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