29. 提肛 Levator ani arises
The levator ani is a broad, thin muscle , situated on the side of the pelvis .
It is attached to the inner surface of the side of the lesser pelvis, and unites with its fellow of the opposite side to form the greater part of the floor of the
pelvic cavity.
It supports the viscera in pelvic cavity, and surrounds the various structures which pass through it.
In combination with the coccygeus muscle , it forms the pelvic diaphragm .
The levator ani is divided into three parts:
Iliococcygeus muscle
Pubococcygeus muscle
Puborectalis muscle
Origin and insertion of fibers
The levator ani arises, in front, from the posterior surface of the superior ramus of the pubis lateral to the symphysis ; behind, from the inner surface of the
spine of the ischium ; and between these two points, from the obturator fascia .
Posteriorly, this fascial origin corresponds, more or less closely, with the tendinous arch of the pelvic fascia, but in front, the muscle arises from the fascia at
a varying distance above the arch, in some cases reaching nearly as high as the canal for the obturator vessels and nerve.
The fibers pass downward and backward to the middle line of the floor of the pelvis; the most posterior are inserted into the side of the last two segments
of the coccyx ; those placed more anteriorly unite with the muscle of the opposite side, in a median fibrous raphé (anococcygeal raphé), which
extends between the coccyx and the margin of the anus .
The middle fibers are inserted into the side of the rectum , blending with the fibers of the Sphincter muscles; lastly, the anterior fibers descend upon the
side of the prostate to unite beneath it with the muscle of the opposite side, joining with the fibers of the sphincter ani externus and transversus
perinei , at the central tendinous point of the perineum .
The anterior portion is occasionally separated from the rest of the muscle by connective tissue.
From this circumstance, as well as from its peculiar relation with the prostate , which it supports as in a sling, it has been described as a distinct
muscle, under the name of Levator prostatæ .
In the female the anterior fibers of the Levator ani descend upon the side of the vagina .
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