Muscles of the Trunk

Transversus perinei superficialis Ischiocavernosus Bulbospongiosus
Transversus perinei profundus Sphincter urethrae

The Transversus perinei superficialis in the female is a narrow muscular slip, which differs but little from the corresponding muscle in the male.

In the B.N.A. the Transversus perinei profundus and the Sphincter urethra: are included finder the term ‘urogenital diaphragm.’

The Bulbospongiosus (Bulbocavernosus) surrounds the orifice of the vagina. It covers the lateral parts of the vestibular bulbs, and is attached posteriorly to the perineal body (central tendinous point of the perineum), where it blends with the Sphincter ani externus. Its fibers pass forwards on each side of the vagina, to be inserted into the corpora cavernosa clitoridis; a fasciculus crosses over the body of the clitoris so as to compress the deep dorsal vein.

Nerve-supply.-The Bulbospongiosus is supplied by the perineal branch of the pudendal nerve.

Actions.—The Bulbospongiosus diminishes the orifice of the vagina. The anterior fibers contribute to the erection of the clitoris by the compression of its deep dorsal vein.

Figure 617
Femal pelvis muscles inferior view - Figure 617
The Ischiocavernosus, smaller than the corresponding muscle in the male, covers the unattached surface of the crus clitoridis. It arises by tendinous and fleshy fibers from the inner surface of the tuberosity of the ischium, behind the crus clitoridis; and .from the adjacent portion of the ramus of the ischium. The muscular fibers end in an aponeurosis which is inserted into the sides and under surface of the crus clitoris.

Nerve-supply.-The Ischiocavernosus is supplied by the perineal branch of the pudendal nerve.

Actions – The Ischiocavernosus compresses the crus clitoridis and retards the return of blood through the veins, and thus serves to maintain the clitoris erect.

The perineal membrane (inferior fascia of the urogenital diaphragm) in the female is wearer than that in the male, and is divided by the aperture of the vagina, with the external coat of which it blends. It covers the following structures: a portion of the urethra, the Transversus perinei profundus and Sphincter urethrae muscles, the greater vestibular glands and their ducts, the internal pudendal vessels, the dorsal nerves of the clitoris, the arteries and nerves of the vestibular bulbs, and a plexus of veins.

The Transversus perinei profundus arises from the ramus of the ischium and runs across behind the vagina to meet the corresponding muscle of the opposite side. The more anterior fibers become lost in the vaginal wall.

Nerve -supply.-The Transversus perinei profundus is supplied by the perineal branch of the pudendal nerve.

Action.-The Transversus perinei profundus helps to fix the perineal body (central tendinous point of the perineum).

The Sphincter urethrae, like the corresponding muscle in the male, consists of external and internal fibers. The external fibers arise on either side from the margin of the inferior ramus of the pubis. They are directed across the pubic arch in front of the urethra, and pass round it to blend with the muscular fibers of the opposite side, between the urethra and vagina. The innermost fibers encircle the lower end of the urethra.

Nerve supply – The Sphincter urethrae is supplied by the perineal branch of the pudendal nerve.

Actions.—The muscles of the two sides act as a constrictor of the urethra.

 


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