Pyramidalis is a small triangular muscle, which is absent in many individuals. It lies in front of the lower part of rectus abdominis within the rectus sheath. Pyramidalis varies considerably in size. It may be larger on one side than the other, absent on one or even doubled.
Origin of Pyramidalis:
Pyramidalis originates inferiorly by tendinous fibers from symphysis pubis and pubic crest.
Insertion of Pyramidalis:
The fleshy portion of the muscle passes upward, diminishing in size as it ascends, and ends by a pointed extremity which is inserted into the linea alba, midway between the umbilicus and pubis.
Blood supply of Pyramidalis:
The major portion of blood supply of pyramidalis comes from the inferior epigastric artery. Some contribution is made by the deep circumflex iliac artery.
Nerve supply to Pyramidalis:
Pyramidalis is innervated by the terminal branches of subcostal nerve (the anterior ramus of 12th thoracic nerve).
Action of pyramidalis:
Pyramidalis has a function of tensing the linea alba, however, the physiologic significance is doubtful.