Autonomic Innervation of the Rectum and Anal Canal

00:01 So now let's turn our attention to the autonomic innovation of the rectum and the anal canal.

00:06 So here we have the muscle layer of the rectum.

00:09 We have the internal anal sphincter, and we can see that both of these are going to be innovated by the inferior hypogastric plexus.

00:17 We see there's also a contribution from parasympathetic and sympathetic in green and blue.

00:23 So let's do what we did similar to the bladder.

00:26 With sympathetic innovation, you're going to have relaxation of the muscle layers within the rectum to allow storage of feces and we're going to have contraction of the internal anal sphincter.

00:37 With parasympathetic that is going to drive defecation, you're going to have contraction of the muscle layer of the rectum and you're going to have relaxation of the internal anal sphincter.

00:49 But also we have the external anal sphincter and this is under somatic nervous control.

00:55 So similar function to that of the bladder by way of the inferior rectal nerve, the somatic nerve you're going to be able to contract and relax the external anal sphincter depending on your urge for defecation.

01:08 So parasympathetic will drive defecation.

01:11 Sympathetic will allow the storage of feces.

01:14 When you have the urge to defecate, you're then in control of it via the conscious contraction or relaxation of the external anal sphincter via the inferior rectal nerve which is somatic in nature.