Autonomic Innervation of the Hindgut, Kidneys, and Adrenal Glands

00:01 Now, let's move on to the hindgut.

00:03 Here we're going to have a look at the innovation of the hindgut.

00:07 We can see that the descending colon, the sigmoid colon, and the rectum.

00:11 These are going to be supplied by the inferior mesenteric plexus.

00:15 So, here we have the inferior mesenteric ganglion, formed by the lumbar splanchnic nerves.

00:21 We can see contributing here in green.

00:23 And here we can see the pelvic splanchnic nerves.

00:26 Remember, these pelvic splanchnic nerves are coming up from the inferior hypogastric plexus.

00:32 So these fibers are coming up from the inferior hypogastric plexus so then merge with the inferior mesenteric plexus to form these periarterial plexuses.

00:43 These are going to supply the descending colon, sigmoid colon, and rectum.

00:48 So, here we can see the inferior mesenteric ganglion contributed to via the lumbar splanchnic nerves for sympathetic.

00:56 Pelvic splanchnic nerves coming up via the inferior hypogastric plexus going towards it to form the inferior mesenteric plexus.

01:06 Now for the first time we can see this superior hypogastric plexus.

01:10 So remember, the inferior hypogastric plexus is lying on the lateral wall of the pelvis.

01:17 It's got parasympathetic and sympathetic nerve fibers within it.

01:21 These pelvic splanchnic nerves are leaving the inferior hypogastric plexus and passing towards the superior hypogastric plexus via those two hypogastric nerves.

01:33 Once they've got here, they form the inferior mesenteric plexus which goes to supply the descending colon, the sigmoid colon and the superior parts of the rectum.

01:43 Next, they will have a little bit of a sideways step and look at the kidneys and adrenal glands.

01:48 So here we can see the greater splanchnic nerve is actually contributing to the adrenal medulla. We can see here.

01:55 And it actually is slightly different.

01:57 In that it does have a very long preganglionic fibers.

02:02 This really is an exception to that sympathetic.

02:05 It doesn't synapse within the celiac ganglion like it did previously.

02:09 It's similar to the parasympathetic.

02:12 So here we can see the posterior vagal trunk is now going towards the kidney alongside the lesser splanchnic nerve.

02:19 But importantly, see how the lesser splanchnic nerve does now synapse in the aorticorenal ganglion.

02:26 So the only exception here is going into the adrenal medulla.

02:30 That is because embryologically, the adrenal gland is derived from the sympathetic nervous system.

02:36 So really is an exception that helps us to characterize the parasympathetic and sympathetic long or short preganglionic fibers.

02:45 Here we can see for the actual kidney how they've reverted to type.

02:51 Long preganglionic fiber for parasympathetic.

02:55 Short preganglionic for sympathetic synapses in the aorticorenal ganglion.

03:02 We can see the lesser splanchnic nerve also has a contribution to the renal ganglion here, And again, a short pre, and a long post.

03:10 The first lumbar spinal nerve will also have a contribution.

03:13 We can see here.

03:14 These together form the renal plexus that takes autonomic nerves towards the kidney.