{{Infobox vein | Name = Rectal venous plexus | Latin = plexus venosus rectalis,<ref>{{Cite web |title=Anatonomina |url=http://www.terminologia-anatomica.org/en/Terms/Occurence/4822 |access-date=2023-07-08 |website=www.terminologia-anatomica.org}}</ref><br>plexus haemorrhoidalis | Image = Gray587.png | Caption = Scheme of the anastomosis of the veins of the rectum. | Image2 = Gray585.png | Caption2 = The veins of the right half of the male pelvis. | DrainsFrom = | Source = | DrainsTo = Superior rectal vein,<br>middle rectal vein(s),<br>inferior rectal veins | Artery = }} The '''rectal venous plexus''' (or '''hemorrhoidal plexus'''<ref>{{Cite web |title=plexus venosus rectalis |url=https://medical-dictionary.thefreedictionary.com/plexus+venosus+rectalis |access-date=2023-07-08 |website=TheFreeDictionary.com}}</ref>) is the venous plexus surrounding the rectum.<ref name=":224">{{Cite book |last=Standring |first=Susan |title=Gray's Anatomy: The Anatomical Basis of Clinical Practice |year=2020 |isbn=978-0-7020-7707-4 |edition=42th |location=New York |pages=1198 |oclc=1201341621}}</ref> It consists of an internal and an external rectal plexus.<ref name=":0">{{Cite book |last1=Moore |first1=Keith L. |title=Clinically Oriented Anatomy |last2=Dalley |first2=Arthur F. |last3=Agur |first3=Anne M. R. |publisher=Wolters Kluwer |year=2018 |isbn=978-1-4963-4721-3 |edition=8th |location=}}</ref>{{Rp|page=598}}'''<ref name=":022" />{{Rp|page=294}}''' It is drained by the superior, middle, and inferior rectal veins. It forms a portosystemic (portocaval) anastomosis.<ref name=":224" /> This allows rectally administered medications to bypass first pass metabolism.{{Citation needed|date=July 2023}}
Despite the inclusion of the term "rectal" into the name, the venous plexus is positionally, functionally, and clinically primarily related to the anal canal.<ref name="Moore-20112">{{cite book |last1=Moore |first1=Keith L. |title=Essential Clinical Anatomy |last2=Dalley |first2=Arthur F. |last3=Agur |first3=Anne M. R. |publisher=Lippincott Williams & Wilkins |year=2017 |isbn=978-1496347213 |edition=6th |pages=598}}</ref>
==Anatomy== The rectal venous plexus consists of an external rectal plexus<ref name=":0" />{{Rp|page=598}}'''<ref name=":022">{{Cite book |last=Sinnatamby |first=Chummy S. |title=Last's Anatomy |publisher= Elsevier Australia|year=2011 |isbn=978-0-7295-3752-0 |edition=12th |pages=}}</ref>{{Rp|page=294}}''' that is situated outside to the muscular wall,<ref name=":224" /><ref name=":0" />{{Rp|page=598}}'''<ref name=":022" />{{Rp|page=294}}''' and an internal rectal plexus<ref name=":0" />{{Rp|page=598}}'''<ref name=":022" />{{Rp|page=294}}''' that is situated in the submucosa<ref name=":022" />{{Rp|page=294}}/deep to the mucosa<ref name=":224" /><ref name=":0" />{{Rp|page=598}} of the rectum and proximal anal canal<ref name=":224" /> at the anorectal junction.<ref name=":0" />{{Rp|page=598}}
===Internal rectal plexus=== 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.{{Citation needed|date=July 2023}}
The internal plexus (sources differ) forms'''<ref name=":0" />{{Rp|page=641}}'''/is continuous distally/inferiorly with'''<ref name=":022" />{{Rp|page=294}}''' the hemorrhoids (the vascular cushions of the anal canal).'''<ref name=":022" />{{Rp|page=294}}<ref name=":0" />{{Rp|page=641}}'''
==== Venous drainage ==== According to the 42nd edition of ''Gray's Anatomy'' (2020), the internal rectal plexus is drained mostly by the superior rectal vein (→inferior mesenteric vein→splenic vein→hepatic portal vein).<ref name=":224" />
According to the 8th edition of ''Clinically Oriented Anatomy'' (2017), the internal rectal plexus is drains mostly into the superior rectal vein superior/proximal to the pectinate line, and into the inferior rectal veins (→internal pudendal vein→internal iliac vein→common iliac vein→inferior vena cava) around the margin of the external anal sphincter inferior/distal to the pectinate line.<ref name=":0" />{{Rp|page=641}}
===External rectal plexus===
==== Venous drainage ==== * The proximal/superior part mostly drains into the superior rectal vein (→inferior mesenteric vein→splenic vein→hepatic portal vein)<ref name=":224" /> * The middle part drains into middle rectal vein(s) (→internal iliac vein→common iliac vein→inferior vena cava)<ref name=":224" /> * The distal/inferior part drains into inferior rectal veins (→internal pudendal vein→internal iliac vein→common iliac vein→inferior vena cava)<ref name=":224" />
=== Structure === 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.{{Citation needed|date=July 2023}}
=== Anastomoses === The rectal venous plexus represents a portosystemic (portocaval) anastomosis.<ref name=":224" />'''<ref name=":022" />'''{{Rp|page=315}} The transition from drainage into the portal system to drainage into the inferior caval system occurs in the region of the anal columns.'''<ref name=":022" />'''{{Rp|page=315}}
It communicates anteriorly with the uterine and vaginal venous plexus in the female, and with the vesical venous plexus in the male.<ref name=":224" />
== Clinical significance == The internal rectal plexus may prolapse into the anal canal to form pathological '''internal haemerrhoids'''; these are often strangulated by the contraction of the anal sphincter, causing ulceration and bleeding.'''<ref name=":0" />{{Rp|page=645}}'''
The external rectal plexus may be affected by blood clots (thrombi), resulting in '''external haemerrhoids'''.'''<ref name=":0" />{{Rp|page=645}}'''
== References == {{Gray's}} {{Reflist}}{{Veins}} {{Portal bar|Anatomy}} {{Authority control}}
Category:Veins of the torso Category:Rectum
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