748 



THE VASCULAR SYSTEMS 



The hemorrhoidal plexus surrounds the rectum, and communicates in front 

 with the vesicoprostatic plexus in the male, and the uterovaginal plexus in the 

 female. It consists of two parts, an internal in the submucosa, and an external 

 outside the muscular coat. Below, the internal plexus presents a series of dilated 

 pouches which are arranged in a circle around the tube immediately above the 

 anal orifice and are connected by transverse branches. 



The lower part of the external plexus is drained by the inferior hemorrhoidal 

 veins into the internal pudic; its middle part by the middle hemorrhoidal vein, 

 which joins the internal iliac; and its upper part by the superior hemorrhoidal 

 vein, which forms the commencement of the inferior mesenteric vein, a tributary 

 of the portal vein. A free communication between the portal and systemic venous 

 systems is established through the hemorrhoidal plexus. 



SUPERIOR 

 HCMORRHOIDAL 



MIDDLE 

 HEMORRHOIDAL 



INFERIOR 

 HEMORRHOIC 



FIG. 523. Scheme of the anastomosis of the veins of the rectum. (Poirier and Charpy.) 



The vesicoprostatic plexus surrounds the prostate gland and the neck of 

 the bladder, and lies partly in the fascial sheath of the prostate and partly between 

 the sheath and the capsule of the gland. In front it receives the deep dorsal vein 

 of the penis; behind, it communicates with the hemorrhoidal and vesical plexuses, 

 and derives tributaries from the vasa deferentia and seminal vesicles. It is drained 

 into the internal iliac veins by one or more vessels on either side. The correspond- 

 ing plexus in the female is named the vesicovaginal. 



The vesical plexus lies on the muscular coat of the bladder, and is best marked 

 toward the base and sides of this viscus; it drains into the vesicoprostatic plexus. 



Applied Anatomy. The veins of the hemorrhoidal plexus are liable to become dilated and 

 varicose, and form piles. This is due to several anatomical reasons: the vessels are contained 

 in very loose, lax connective tissue, so that they get less support from surrounding structures 

 than most other veins, and are less capable of resisting increased blood pressure; the condition 

 is favored by gravitation, being influenced by the erect posture, either sitting or standing, and 

 by the fact that the superior hemorrhoidal and portal veins have no valves; the veins pass 



