Pyramidalis muscle

Structure

The pyramidalis muscle is part of the anterior abdominal wall. Inferiorly, the pyramidalis muscle attaches to the pelvis in two places: the pubic symphysis and pubic crest, arising by tendinous fibers from the anterior part of the pubis and the anterior pubic ligament.

Superiorly, the fleshy portion of the pyramidalis 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.

Nerve supply

The pyramidalis muscle is innervated by the ventral portion of T12.

Blood supply

The pyramidalis is most commonly supplied by a separate branch of the inferior epigastric artery, but it may also be supplied by the superior epigastric artery in few cases. It is drained by the respective named veins.

Variation

The pyramidalis muscle is present in 80% of human population. It may be absent on one or both sides; the lower end of the rectus then becomes proportionately increased in size.

Occasionally, it is doubled on one side, and the muscles of the two sides are sometimes of unequal size. It may also extend higher than the usual level.

Function

The pyramidalis muscle tenses the linea alba when contracting.

Clinical significance

While making the longitudinal incision for a classical caesarean section, the pyramidalis muscle is used to determine midline and location of the linea alba.

Additional images

File:Gray235.png|Right hip bone viewed from outside, showing a small line where the pyramidalis attaches

References

References

1. (2016-01-01). "Chapter 16 - In Situ Volumetric Muscle Repair". Academic Press.
2. (November 2024). "Morphology and arterial supply of the pyramidalis muscle in an Australian female population using computed tomography angiography". Surgical and Radiologic Anatomy.
3. "7 Vestigial Features of the Human Body".