Pyramidalis muscle
Encyclopedia
The pyramidalis is a small and triangular muscle, anterior to the Rectus abdominis, and contained in the rectus sheath
.
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.
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.
the pyramidalis is used to determine midline and location of the linea alba.
Rectus sheath
The Rectus sheath is formed by the aponeuroses of the Obliqui and Transversus. It contains the Rectus abdominis and Pyramidalis muscles.It can be divided into anterior and posterior laminae....
.
Attachments and actions
Inferiorly, it attaches to the pubic symphysisPubic symphysis
The pubic symphysis or symphysis pubis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis...
and pubic crest
Pubic crest
Medial to the pubic tubercle is the pubic crest, which extends from this process to the medial end of the bone.It affords attachment to the inguinal falx, and to the External Abdominal Oblique and Pyramidalis....
, arising by tendinous fibers from the anterior part of the pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons 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
Linea alba
The linea alba is a fibrous structure that runs down the midline of the abdomen in humans and other vertebrates. The name means white line and the linea alba is indeed white, being composed mostly of collagen connective tissue....
, midway between the umbilicus
Navel
The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...
and pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons 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.
Surgical Landmark
While making the longitudinal inscision for a classical caesarean sectionCaesarean section
A Caesarean section, is a surgical procedure in which one or more incisions are made through a mother's abdomen and uterus to deliver one or more babies, or, rarely, to remove a dead fetus...
the pyramidalis is used to determine midline and location of the linea alba.