Neurovasculature of the rectum and anal canal
After going through this study unit, you will be able to:
- Name the blood vessels and nerves that supply the rectum and anal canal
- Understand their anatomical relations, functions and clinical significance
- Successfully identify the major nerves and vessels in a quiz environment
The rectum and anal canal are supplied by the three anorectal arteries and drained by the three anorectal veins; superior, middle and inferior. Until recently, these vessels have been known as the “rectal” arteries and veins, From superior to inferior, the arteries branch from the inferior mesenteric, internal iliac and internal pudendal arteries. The veins follow the same path as arteries, draining into the corresponding vessels; inferior mesenteric, internal iliac and internal pudendal veins. The anorectal veins form a hemorrhoidal venous plexus which has a special clinical significance, as it can swell and result with different types of hemorrhoids.
The following video tutorial will explain the anatomy and course of the three anorectal arteries and veins.
The innervation or rectum and anal canal is a bit more complex, involving an intrinsic and an extrinsic component.
- The intrinsic component is the enteric nervous system, consisting of the submucosal (Meissner’s) and myenteric (Auerbach’s) plexuses which control the peristaltic contractions and mucous secretions.
- The extrinsic component for the rectum and upper part of anal canal is the autonomic nervous system. It consists of the sympathetic and parasympathetic portions which are in control of inducing/containing the defecation. In a nutshell, the autonomic nerves synapse within/pass through the superior and inferior hypogastric plexuses which give off branches to the rectum and upper portion of anal canal.
- The lower portion of anal canal is extrinsically supplied by the somatic nervous system via the pudendal nerve. The somatic innervation imposes the conscious control of the defecation by controlling the external anal sphincter.
The following video tutorial integrates the anatomy and innervation of the rectum and anal canal.
Take a quiz
Take our quiz to practice and reinforce what you have learned throughout the video.
Feeling ready to integrate and solidify your knowledge? Try out this fully customizable quiz about the anatomy of the whole large intestine.
Browse our atlas gallery to further analyze the courses and relations of the anorectal vessels.
|Superior anorectal artery||
Origin: Inferior mesenteric artery
Supply: Upper two thirds of the rectum
|Middle anorectal artery||
Origin: Internal iliac artery
Supply: Middle and lower parts of the rectum
|Inferior anorectal artery||
Origin: Internal pudendal artery (branch of the internal iliac artery)
Supply: Anal canal, internal and external anal sphincter, perianal skin
|Anorectal veins||Superior anorectal veins → Superior mesenteric vein
Middle anorectal veins → Internal iliac vein
Inferior anorectal veins → Internal pudendal vein (drains into the internal iliac vein)
|Intrinsic innervation of rectum and anal canal||
Enteric nervous system
Submucosal plexus (of Meissner)
Enteric plexus (of Auerbach)
Control peristaltic contractions and mucous secretions.
|Extrinsic innervation of rectum and upper half of anal canal||
Autonomic nervous system
Sympathetic input: Sacral splanchnic nerves
Parasympathetic input: Pelvic splanchnic nerves
Fibers from splanchnic nerves synapse within/pass through the superior and inferior hypogastric plexuses and give the superior anal (rectal) nerves.
|Extrinsic innervation of lower half of anal canal||
Somatic nervous system
Pudendal nerve: Inferior anal (rectal) nerve
Provides voluntary control over external anal sphincter and defecation