Neurovasculature of the rectum and anal canal

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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 of 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.

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Summary