The transversus abdominis is a flat and broad muscle which is situated in the anterolateral aspect of the abdominal wall, occupying the deepest position. It is composed of transverse fibers which run horizontally across the anterolateral part of the abdomen, beneath the abdominal internal oblique muscle, whose fibers travels down obliquely.
The transversus abdominis muscle originates from the inner surfaces of the lower six costal cartilages, lumbar fascia, inner lip of iliac crest, and the lateral two third of the inguinal ligament. With its fibers traveling horizontally forwards, it ends in aponeurosis, which extends behind the rectus abdominis muscle. This aponeurosis contributes to the formation of the linea alba on the midline.
A few fibers run out of the lower parts of the transversus abdominis to meet similar fibers of the abdominal internal oblique to give shape to the cremaster muscle. A laterally convex line is formed at the junction of the muscular fibers with the aponeurosis; it is called the linea semilunaris.
Action/function
It flattens the abdominal wall, compressing abdominal contents.
Blood Supply
The transversus abdominis muscle is supplied by the inferior and superior epigastric as well as by musculophrenic artery.
Nerve Supply
It is innervated by the intercostal, iliohypogastric, and the ilioinguinal nerves.
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