Pyramidalis muscle

Pyramidalis muscle
The Transversus abdominis, Rectus abdominis, and Pyramidalis. (Pyramidalis labeled at bottom center.)
Latin	musculus pyramidalis
Gray's	subject #118 416
Origin	pubic symphysis and pubic crest
Insertion	linea alba
Artery:
Nerve:	Subcostal nerve (T12)
Action:	tensing the linea alba
Dorlands /Elsevier	m_22/12550348

The pyramidalis is a muscle that is considered insignificant in humans. It is small and triangular, anterior to the Rectus abdominis, and contained in the rectus sheath.

Attachments and actions

Inferiorly, it attaches to 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 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.

Therefore, when contracting, it has the function of tensing the linea alba.

Variations

It is absent in 20% of normal humans.

This muscle may be absent on one or both sides; the lower end of the rectus then becomes proportionately increased in size.

Occasionally it is double on one side, and the muscles of the two sides are sometimes of unequal size.

It may extend higher than the usual level.

Innervation

The muscle is innervated by the ventral portion of T12.

Additional images

• 

  Right hip bone. External surface.

External links

• -1241120688 at GPnotebook
• LUC pyr
• SUNY Labs 35:11-0100 - "Anterior Abdominal Wall: The Pyramidalis Muscle"
• SUNY Anatomy Image 7283
• Cross section at UV pelvis/pelvis-female-17

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