The pyramidalis muscle is a small triangular
muscle, anterior to the
rectus abdominis muscle
The rectus abdominis muscle, ( la, straight abdominal) also known as the "abdominal muscle" or simply the "abs", is a paired straight muscle. It is a paired muscle, separated by a midline band of connective tissue called the linea alba. It ex ...
, and contained in the
rectus sheath
The rectus sheath, also called the rectus fascia,. is formed by the aponeuroses of the transverse abdominal and the internal and external oblique muscles. It contains the rectus abdominis and pyramidalis muscles.
Structure
The rectus sheat ...
.
Structure
The pyramidalis muscle is part of the anterior abdominal wall. Inferiorly, the pyramidalis muscle attaches to the
pelvis in two places: the
pubic symphysis
The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubi ...
and
pubic crest
Medial to the pubic tubercle is the pubic crest, which extends from this process to the medial end of the pubic bone.
It gives attachment to the conjoint tendon, the rectus abdominis, the abdominal external oblique muscle, and the pyramidalis mu ...
, arising by tendinous fibers from the anterior part of the
pubis and the
anterior pubic ligament.
Superiorly, the fleshy portion of the pyramidalis 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.
Nerve supply
The pyramidalis muscle is innervated by the ventral portion of
T12.
Blood supply
The
inferior and
superior epigastric arteries supply blood to the pyramidalis muscle.
Variation
The pyramidalis muscle is present in 80% of human population.
It may be absent on one or both sides; the lower end of the rectus then becomes proportionately increased in size.
Occasionally, it is doubled on one side, and the muscles of the two sides are sometimes of unequal size. It may also extend higher than the usual level.
Function
The pyramidalis muscle tenses the
linea alba when contracting.
Clinical significance
While making the longitudinal incision for a classical
caesarean section, the pyramidalis muscle is used to determine midline and location of the
linea alba.
Additional images
File:Gray235.png, Right hip bone viewed from outside, showing a small line where the pyramidalis attaches
References
External links
* - "Anterior Abdominal Wall: The Pyramidalis Muscle"
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Muscles of the torso