Muscle · Core

Pyramidalis

Musculus pyramidalis

A small triangle of muscle in the very bottom of the rectus sheath, sitting in front of the lower end of rectus abdominis with its base on the pubis and its apex pointing up the midline. It ends in the linea alba — the fibrous seam running down the centre of the belly — roughly halfway between the pubis and the navel. Its only job is to tension that seam. It is absent in a proportion of people and it is on the small side even when present, so it is met more often as an anatomical detail of the lower abdominal wall than as a muscle anyone treats.