THE NERVE SYSTEM 



supply the descending and sigmoid flexure of the colon; and the superior hemor- 

 rhoidal plexus (plexus hemorrhoidalis superior), which supplies the upper part 

 of the rectum and joins in the pelvis with branches from the pelvic plexus. 



The Hypogastric Plexus (Plexus Hypogastricus) (Figs. 780, 786). 



The hypogastric plexus supplies the viscera of the pelvic cavity. It is situated 

 in front of the promontory of the sacrum, between the two common iliac arteries, 

 and is formed by the union of numerous filaments, which descend on each side 

 from the abdominal aortic plexus and from the lumbar ganglia. This plexus con- 

 tains no evident ganglia; it bifurcates, below, into two lateral portions, right and 

 left, which form the pelvic plexuses. 



The Pelvic Plexuses. 



The pelvic plexuses supply the viscera of the pelvic cavity, and are situated at 

 the side of the rectum in the male, and at the sides of the rectum and vagina 

 in the female. They are formed by a continuation of the hypogastric plexus, by 

 the visceral branches from the second, third, and fourth sacral nerves, and by a 

 few filaments from the first two sacral ganglia. At the points of junction of 

 these nerves small ganglia are found. From these plexuses numerous branches 

 are distributed to the rectum and bladder in the male, and to the rectum, bladder, 

 uterus, and vagina in the female. They accompany the branches of the internal 

 iliac artery. These secondary plexuses are (1) the inferior hemorrhoidal, (2) 

 vesical, (3) prostatic, (4) vaginal, and (5) uterine plexuses. 



The Inferior Hemorrhoidal Plexus (plexus haemorrhoidalis inferior] arises from 

 the upper part of the pelvic plexus. It supplies the rectum, joining with branches 

 of the superior hemorrhoidal plexus. 



The Vesical Plexus (plexus vesicalis) arises from the fore part of the pelvic 

 plexus. The nerves composing it are numerous, and contain a large proportion 

 of spinal nerve fibres. They accompany the vesical arteries, and are distributed 

 to the side and base of the bladder. Numerous filaments also pass to the vesiculae 

 seminales and vasa deferentia; those accompanying the vas deferens join, on the 

 spermatic cord, with branches from the spermatic plexus. 



The Prostatic Plexus (plexus prostaticus) is continued from the lower part of 

 the pelvic plexus. The nerves composing it are of large size. They are distributed 

 to the prostate gland, seminal vesicles, and erectile tissue of the penis. The 

 nerves supplying the erectile tissue of the penis consist of two sets, the small and 

 large cavernous nerves. They are slender filaments, which arise from the fore part 

 of the prostatic plexus, and, after joining with branches from the internal pudic 

 nerve, pass forward beneath the pubic arch. 



The small cavernous nerves (nn. cavernosi penis mirwres) perforate the fibrous 

 covering of the penis, near its root. 



The large cavernous nerve ('/?, cavernosus penis major) passes forward along the 

 dorsum of the penis, joins with the dorsal nerve of the penis, and is distributed 

 to the corpora cavernosa and corpus spongiosum. 



The uterine and vaginal plexuses in reality constitute one plexus, the utero- 

 vaginal plexus (plexus uterovaginalis). 



The Vaginal Plexus arises from the lower part of the pelvic plexus. It is dis- 

 tributed to the walls of the vagina, to the erectile tissue of the vestibule, and to the 

 clitoris. ^ The nerves composing this plexus contain, like the vesical, a large 

 proportion of spinal nerve fibres. 



The Uterine Plexus accompanies the uterine artery to the side of the uterus 

 between the layers of the broad ligament; it communicates with the ovarian plexus. 



