Pyramidalis muscle

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Pyramidalis muscle
Gray397.png
The Transversus abdominis, Rectus abdominis, and Pyramidalis. (Pyramidalis labeled at bottom center.)
Latin musculus pyramidalis
Gray's p.416
Origin pubic symphysis and pubic crest
Insertion linea alba
Nerve Subcostal nerve (T12)
Actions tensing the linea alba
TA A04.5.01.007
FMA FMA:15568
Anatomical terms of muscle

The pyramidalis is a small and triangular muscle, anterior to the Rectus abdominis, and contained in the rectus sheath.

Attachments and actions[edit]

Inferiorly, it 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 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[edit]

The Pyramidalis muscle is absent in 20% of normal humans.[1] 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 also extend higher than the usual level.

Innervation[edit]

The muscle is innervated by the ventral portion of T12.

Blood Supply[edit]

The inferior and superior epigastric arteries are responsible for supplying blood to this muscle.

Surgical Landmark[edit]

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

Additional images[edit]

References[edit]

  1. ^ Keith Lean Moore; Arthur F. Dalley (1999). Anatomy. Lippincott Williams & Wilkins. p. 180. ISBN 978-0-683-06141-3. Retrieved 1 December 2012. 

External links[edit]