430 MYOLOGY 



and ischium to the extent of 1.25 to 2 cm., and from the neighboring fasciae. 

 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 raphe. 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 perinsei superficialis. Ischiocavernosus. 



Bulbocavernosus. Transversus perinsei profundus. 



Sphincter urethrse membranaceae. 





The Transversus perinaei superficialis (Transversus perincei; Superficial trans- 

 verse 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 situa- 

 tion 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 vagina) 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 pubic 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 perfor- 

 ated by the urethra. Its posterior border is continuous, as in the male, with the 

 deep layer of the superficial fascia around the Transversus perinsei 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 



