Musculus pyramidalis

The pyramidalis muscle is a small paired triangular muscle of the lower anterior abdominal wall that is rudimentary and variably present in humans.

Summary

• origin: pubic symphysis and pubic crest
• insertion: linea alba at the midway point between umbilicus and pubis
• innervation: ventral T12 spinal nerve (variable)
• action: uncertain; thought to tense the linea alba

Gross anatomy

The pyramidalis muscle has its origin from the bony pelvis, where it is attached to the pubic symphysis and pubic crest. The fibers run superiorly and medially to insert into the linea alba at a point midway between umbilicus and pubis.

It lies within the rectus sheath, anterior to the rectus abdominis muscle.

Innervation

The nerve supply to the muscle is from ventral part of T12 spinal segment although this has been reported as being quite variable .

Variant anatomy

• absent in ~20% of cases (reported range of absence is 10-70%)
• may be present only unilaterally

Siehe auch:

• Bauchmuskulatur