|Vein: Hemorrhoidal plexus|
|Scheme of the anastomosis of the veins of the rectum.|
|The veins of the right half of the male pelvis.|
|Latin||plexus venosus rectalis, plexus haemorrhoidalis|
|Gray's||subject #173 676|
|Drains to||superior rectal vein|
A free communication between the portal and systemic venous systems is established through the hemorrhoidal plexus.
It consists of two parts, an internal in the submucosa, and an external outside the muscular coat.
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 rectal veins into the internal pudendal vein
- The middle part of the external plexus is drained by the middle rectal vein which joins the internal iliac vein.
- The upper part of the external plexus is drained by the superior rectal vein which forms the commencement of the inferior mesenteric vein, a tributary of the portal vein.
The veins of the hemorrhoidal plexus are contained in very loose, connective tissue, so that they get less support from surrounding structures than most other veins, and are less capable of resisting increased blood-pressure.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.