n :  any of three veins that receive blood from the rectal venous plexus:  a  :  one draining the lower part of the rectal venous plexus and emptying into the internal pudendal vein - called also inferior hemorrhoidal vein , inferior rectal vein   b  :  one draining the bladder, prostate, and seminal vesicle by way of the middle part of the rectal venous plexus and emptying into the internal iliac vein - called also middle hemorrhoidal vein , middle rectal vein   c  :  one draining the upper part of the rectal venous plexus and forming the first part of the inferior mesenteric vein - called also superior hemorrhoidal vein , superior rectal vein  .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.