Pyramidalis muscle

Dr Henry Knipe and Balaji Vasu et al.

The pyrimidalis is a paired, small triangular muscle that is rudimentary in humans.

  • 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

The pyramidalis muscle has its origin from the bony pelvis, where it is attached to the pubic symphysis and pubic crest. The fibres 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

The nerve supply to the muscle is from ventral part of T12 spinal segment although this has been reported as being quite variable 3

  • absent in ~20% of cases (reported range of absence is 10-70%) 3
  • may be present only unilaterally
Anatomy: abdominopelvic
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Article information

rID: 27059
Section: Anatomy
Synonyms or Alternate Spellings:
  • Pyrimidalis

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