Rectum and Anal Canal – Autonomic Nerves of Abdominopelvic Organs

by James Pickering, PhD

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    00:00 So an important play between the somatic and the autonomic nervous system.

    00:04 A similar arrangement happens here, when we are looking at the rectum and the anal canal.

    00:10 And in this diagram, unlike the previous, we can actually see the hypogastric plexus that I have been talking about.

    00:18 So just spend some time just reviewing this now.

    00:21 We can see we have the coeliac plexus and the coeliac ganglion around the coeliac trunk here. And you generally have a flow of autonomic nerves down the aorta, enabling parasympathetic fibers to pass down from the vagus.

    00:36 Allowing the sympathetic fibers from coeliac trunk to actually pass down and you can have the flow of autonomic fibers from superior mesenteric plexus down to the inferior mesentery plexus. And then it carries on down to the bifurcation of the aorta.

    00:55 And at the bifurcation of the aorta, you can find we have the superior hypogastric plexus.

    01:04 The superior hypogastric plexus.

    01:08 This is going to be a mixed plexus. It's contains both parasympathetic and sympathetic.

    01:13 We can then see if we look at our S2, 3, 4 parts of our sacral plexus.

    01:21 This is going to give rise to our pelvic splanchnic nerves.

    01:26 These pelvic splanchnic nerves then run towards the internal iliac and they meet autonomic fibers coming down from the superior hypogastric fibers.

    01:39 From the superior hypogastric plexus.

    01:41 And these fibers are running down as hypogastric nerves.

    01:45 They merge with the pelvic splanchnic nerves to form the inferior hypogastric plexus.

    01:54 So we had one superior hypogastric plexus gives rise to two hypogastric nerves.

    02:00 These hypogastric nerves merge with pelvic splanchnic nerves to form the inferior hypogastric plexus.

    02:08 We're concerned with the rectum. So this inferior hypogastric plexus gives autonomic fibers that go towards the rectum and they form this rectal plexus.

    02:20 We can then follow the formation of the rectal plexus.

    02:24 Sympathetic, we have these lumbar splanchnic nerves that pass in to the inferior mesenteric plexus.

    02:31 They then run down to the superior hypogastric plexus and then they communicate with the inferior hypogastric plexus via hypogastric nerves and here they get to the rectal plexus.

    02:43 Parasympathetic is going to be via pelvic splanchnic nerves which we can see here and these pass into the left and right inferior hypogastric plexus which gives rise to the rectal plexus.

    02:58 This is the autonomic control of the rectum.

    03:01 However, this controls our ability to defecate and again we have the sensation that we need to defecate.

    03:10 Yeah, we also have the ability to limit ourselves from defecating. We can control it.

    03:18 And that is because inferior to the pectinate line we have the external anal sphincter.

    03:26 The external anal sphincter is innervated via the inferior rectal nerve. And this is a somatic branch from S2, S3, S4, we can see it here.

    03:38 Now confusing I appreciate, the S2, 3, 4 gives rise to parasympathetic fibers.

    03:45 It also gives rise to the somatic pudendal nerve and this controls the external anal sphincter.

    03:53 So when you have the urge to defecate, you can contract this sphincter.

    03:57 You don't walk around with it contracted.

    03:59 When you have the urge to defecate you can contract this sphincter.

    04:02 You can make your way to a toilet. Then you control, you relax it and you defecate.

    04:08 So that's the autonomic innervation to the rectum and anal canal.

    About the Lecture

    The lecture Rectum and Anal Canal – Autonomic Nerves of Abdominopelvic Organs by James Pickering, PhD is from the course Pelvis.

    Included Quiz Questions

    1. Pudendal
    2. Lumbar splanchnic
    3. Pelvic splanchnic
    4. Hypogastric
    5. Superior hypogastric
    1. Pelvic
    2. Greater
    3. Lesser
    4. Lumbar
    5. Least
    1. Lumbar
    2. Pelvic
    3. Pudendal
    4. Inferior rectal
    5. Thoracic

    Author of lecture Rectum and Anal Canal – Autonomic Nerves of Abdominopelvic Organs

     James Pickering, PhD

    James Pickering, PhD

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