Rectus abdominis muscle

Rectus abdominis muscle
Human rectus abdominis muscle
origin
5th to 7th costal cartilage , sternum
approach
Pelvis (crista pubica)
function
Abdominal press, elevation of the pelvis, lowering of the thorax, trunk flexion
Innervation
Nervi intercostales (7th-12th branches)

The rectus abdominis muscle ( lat. For straight abdominal muscle ) begins on the chest , where it arises on the front surface of the fifth to seventh costal cartilage and on the sword process ( processus xiphoideus ) of the sternum . It pulls down to the pool in two lanes . There it is attached to the upper pubic branch between the pubic symphysis and the pubic tuberosity ( tuberculum pubicum ).

The straight abdominal muscle is subdivided by three to four intermediate tendons ( intersectiones tendineae ), so that a so-called “ washboard abdomen” appears when the muscles are well developed and there is hardly any subcutaneous fat . Between the left and right rectus abdominis muscles, the midline is the linea alba (“white line”) as a stiff connective tissue seam of the abdomen. A divergence of the two muscles in the area of ​​the linea alba is known as diastasis recti . Above the navel, the muscle lies completely within the so-called rectus sheath , which consists of aponeuroses of the lateral abdominal muscles. The upper portion of the muscle is mainly attached to the cartilage of the fifth rib.

Sometimes there is only one or two intermediate tendons below the belly button. Very rarely the intermediate tendons are completely absent.

variation

The sternalis muscle can be a variation of the pectoralis major or the abdominal rectus. Some fibers are sometimes connected to the costoxiphoid ligament and to the side of the xiphoid process .

function

The rectus abdominis muscle is an important postural muscle. The straight abdominal muscle ensures that the chest is pulled towards the legs and the torso is bent as a result. On the other hand, when the upper body is fixed, the front edge of the pool is raised. If both the upper body and the pelvis are fixed, the tension in the muscle serves to support the abdominal press . The muscle also helps with breathing and plays an important role in forceful exhalation, which can be observed after physical exercise and also in conditions with difficult exhalation such as emphysema . The antagonist is the erector spinae muscle .

Blood supply

The straight abdominal muscle has many arterial inflows. The inferior epigastric artery and vein (or veins) run independently on the posterior surface of the rectus abdominis muscle, enter the rectus sheath at the semicircular line and supply the lower part of the muscle. The superior epigastric artery , a terminal branch of the internal thoracic artery , supplies the upper part with blood. Eventually, numerous small tributaries come from the lower six anterior intercostal arteries .

gallery

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  Rectus abdominis muscle in a youth gymnast,

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  at a gymnast and

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  at a diver.

Individual evidence

1. ^ Herbert Lippert: Textbook anatomy. 2nd Edition. Munich 1990, ISBN 3-541-10062-1 , p. 156.