Henry Gray (18251861). Anatomy of the Human Body. 1918.
and ischium to the extent of 1.25 to 2 cm., and from the neighboring fasciæ. They arch across the front of the urethra and bulbourethral glands, pass around the urethra, and behind it unite with the muscle of the opposite side, by means of a tendinous raphé. Its innermost fibers form a continuous circular investment for the membranous urethra.
Nerve Supply.The perineal branch of the pudendal nerve supplies this group of muscles.
Actions.The muscles of both sides act together as a sphincter, compressing the membranous portion of the urethra. During the transmission of fluids they, like the Bulbocavernosus, are relaxed, and only come into action at the end of the process to eject the last drops of the fluid.
2. B. The Muscles of the Urogenital Region in the Female(Fig. 408).
Transversus perinæi superficialis.
Transversus perinæi profundus.
Sphincter urethræ membranaceæ.
The Transversus perinæi superficialis (Transversus perinæi; Superficial transverse perineal muscle) in the female is a narrow muscular slip, which arises by a small tendon from the inner and forepart of the tuberosity of the ischium, and is inserted into the central tendinous point of the perineum, joining in this situation with the muscle of the opposite side, the Sphincter ani externus behind, and the Bulbocavernosus in front.
Action.The simultaneous contraction of the two muscles serves to fix the central tendinous point of the perineum.
The Bulbocavernosus (Sphincter vaginæ) surrounds the orifice of the vagina. It covers the lateral parts of the vestibular bulbs, and is attached posteriorly to the central tendinous point of the perineum, where it blends with the Sphincter ani externus. Its fibers pass forward on either side of the vagina to be inserted into the corpora cavernosa clitoridis, a fasciculus crossing over the body of the organ so as to compress the deep dorsal vein.
Actions.The Bulbocavernosus diminishes the orifice of the vagina. The anterior fibers contribute to the erection of the clitoris, as they are inserted into and are continuous with the fascia of the clitoris, compressing the deep dorsal vein during the contraction of the muscle.
The Ischiocavernosus (Erector clitoridis) is smaller than the corresponding muscle in the male. It covers the unattached surface of the crus clitoridis. It is an elongated muscle, broader at the middle than at either end, and situated on the side of the lateral boundary of the perineum. It arises by tendinous and fleshy fibers from the inner surface of the tuberosity of the ischium, behind the crus clitoridis; from the surface of the crus; and from the adjacent portion of the ramus of the ischium. From these points fleshy fibers succeed, and end in an aponeurosis, which is inserted into the sides and under surface of the crus clitoridis.
Actions.The Ischiocavernosus compresses the crus clitoridis and retards the return of blood through the veins, and thus serves to maintain the organ erect.
The fascia of the urogenital diaphragm in the female is not so strong as in the male. It is attached to the public arch, its apex being connected with the arcuate pubic ligament. It is divided in the middle line by the aperture of the vagina, with the external coat of which it becomes blended, and in front of this is perforated by the urethra. Its posterior border is continuous, as in the male, with the deep layer of the superficial fascia around the Transversus perinæi superficialis.
Like the corresponding fascia in the male, it consists of two layers, between which are to be found the following structures: the deep dorsal vein of the clitoris, a portion of the urethra and the Constrictor urethra muscle, the larger vestibular