The hemorrhoidal plexus (or rectal venous plexus) surrounds the rectum, and communicates in front with the vesical venous plexus in the male, and the uterovaginal plexus in the female. A free communication between the portal and systemic venous systems is established through the hemorrhoidal plexus. [ http://en.wikipedia.org/wiki/Rectal_venous_plexus ]