Quick Facts
Origin: Medial portion of anorectal venous plexus.
Course: Travels through the mesorectum to drain into the internal iliac vein.
Tributaries: Anorectal venous plexus.
Drainage: Medial third of rectum and mesorectum.
Origin
The middle anorectal veins are formed in the anorectal venous plexus surrounding the anal canal and rectum.
Course
The number and caliber of middle anorectal vessels are highly variable. They originate within the anorectal venous plexus and travel along the surface of levator ani to drain into the systemic circulation via the internal iliac veins.
Tributaries
The middle anorectal veins communicate with the external anorectal plexus. They may also receive tributaries from the bladder, seminal gland (or vesicle), and prostate in males, or the posterior portion of the vagina in females. They also form anastomoses with the superior and inferior anorectal veins through the anorectal venous plexus.
Structures Drained
They drain the middle one third of the rectum and mesorectum via the anorectal venous plexus and the muscularis externa of the ampulla of the anal canal.
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Vein
A venous sinus is a vein with a thin wall of endothelium that is devoid of smooth muscle to regulate its diameter.
