Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we're going to be talking about the nerves of the female pelvis. Now, the innervation of the female pelvis involves both somatic nerves for then motor and sensory functions and also visceral nerves or autonomic for then innervation of the viscera or the organs. And, throughout this tutorial, I’m going to be talking about the somatic nerves and visceral nerves that will be innervating then the female pelvis but I will be using this image here of the cut female pelvis that we’re now looking at and you see here a few organs were retracted namely the rectum and the uterus. You can also see here the urinary bladder and all these yellow strings here that are then the different nerves that we’re going to be highlighting and describing throughout this tutorial.
So, let’s start with the somatic nerves that are responsible for motor and sensory functions and we’re now highlighting here on the image, as you can see here – the ventral rami of the lumbar nerves. Now, these rami form the lumbar plexus which includes several nerves of the pelvic cavity and the thigh. The ventral rami of the lumbar nerves form the lumbar plexus from L1 to L4 which is something worth keeping in mind.
Now, moving on to the next structure that we’re going to be highlighting here, notice this nerve here – this thin nerve – which is known as the obturator nerve. We’re seeing here then the left obturator nerve because the right one was removed when we cut here the female pelvis. But to say that the obturator nerve is an important nerve that provides sensory innervation to the skin of the medial aspect of the thigh while also providing motor innervation to the pectineus muscle and the adductor muscles of the lower thigh.
Now, there is also here an image of the anterior view of the pelvis. Now, we’re left with bones and nerves where we then highlight the obturator nerves. I would like to add here that this nerve will be giving off an anterior, also posterior and cutaneous branch and the nerve itself arises from the anterior division of the second, third, and fourth lumbar nerves as you can clearly see here on this image. So, second, third, and fourth lumbar nerves.
The next structure I would like to highlight here on this image of the pelvis – the female pelvis – notice here hidden behind all these structures, all this network, which is known as the sacral plexus. So, we’re highlighting now the sacral plexus that besides the lumbar plexus that gives off the obturator nerves, another very important plexus is then this one that we’re seeing now, the sacral plexus.
Now, the sacral plexus is comprised of the anterior division of S1 nerve as well as parts of the anterior divisions of S2 and S3 nerves. Sacral plexus will be providing sensory as well as motor innervation to the, to parts of the pelvis, the posterior part of the thigh, and part of the lower leg and foot. Important note here that this plexus will be giving rise to one important nerve known as the pudendal nerve which happens to be just coincidentally, this nerve that we’re seeing now highlighted in green, these two nerves, now seen here from the inferior view of the female pelvis. As you can see, we stripped a lot of structures here to be left with mainly muscles, some of the muscles of the pelvic diaphragm, and then the hip bones, and then the nerves here which we’re highlighting, these are then the pudendal nerves.
Now, the pudendal nerve is the major somatic nerve of the perineum. It is a paired nerve as you see here – so two nerves one on each side – and arises from the level of S2 to S4 vertebrae. You can also guess here from this image that it will be providing sensory innervation to external genitalia including the skin around the anus and also the perineum. Will be also providing motor innervation to the muscles of the perineum and the floor of the pelvis. Now, the pudendal nerve leaves the pelvic cavity through the greater sciatic foramen which you can see here also in this image and then enters the anal triangle of the perineum.
Next nerves that we’re going to be highlighting here still on this image, these are then the perineal nerves. They are major branches of then the pudendal nerve which we talked about before and is now seen here but not highlighted. Now, the pudendal nerve which passes into the urogenital triangle and gives rise to motor and cutaneous branches. The motor branches innervate the skeletal muscles in the superficial and deep perineal pouches.
And now that we have covered the major somatic nerves of the female pelvis, it’s time to move on to the visceral or autonomic nerves that will be innervating this particular region of the body, and we’re going to start off with this one that you see here highlighted in green which is known as the lumbar ganglion of the sympathetic trunk.
Now, the lumbar ganglia of the sympathetic trunk are usually comprised of four paravertebral ganglia at the lumbar portion of the sympathetic trunk. Now, presynaptic axons from the sympathetic trunk at the level of L1 and L2 pass through the lumbar ganglia and form the splanchnic nerves. Now, presynaptic neurons from the portion of the sympathetic trunk supply the organs of the pelvis. The lumbar ganglia of the sympathetic trunk are located on either side of the lumbar vertebral column. Right now, we’re only seeing those that are then located on the right side of the vertebral column. Note here then the fifth lumbar vertebra and the sacrum.
Next on our list seen here highlighted in green, we’re now seeing these filaments here – these structures highlighted in green – which are known as the lumbar splanchnic nerves. They arise from the lumbar ganglia of the sympathetic trunk usually comprised of four nerves. They originate at the level of L1 and L2 and contain preganglionic sympathetic fibers as well as general visceral afferent fibers. Now, these fibers synapse with postsynaptic neurons on the inferior mesenteric ganglion but can also synapse with neurons found on the lumbar ganglia or the inferior hypogastric plexus. Now, the postsynaptic fibers from the lumbar splanchnic nerves will be innervating the smooth muscles of vessels that supply the pelvic viscera and the lower ureter.
Another important structure worth noting here and highlighting, these structures which are known as singularly as the gray ramus communicans and, as plural, gray rami communicantes. They also arise from the lumbar ganglia of the sympathetic trunk and they send communicating branches to the spinal nerves from adjacent paravertebral ganglia of the sympathetic trunk. Now, these rami containing afferent and efferent fibers will be carrying postganglionic fibers from the sympathetic ganglia to the spinal nerves and can be found at every level of your spinal cord.
The next structure we’re going to be highlighting here on this image is known as the superior hypogastric plexus. The superior hypogastric plexus receives branches from the lumbar ganglia of the sympathetic trunk via the lumbar splanchnic nerves at the level of L1 and L2 vertebrae. Now, as you can see here, this plexus will continue then as the right and left hypogastric nerves. Now, branches from this plexus will be then innervating the ureter and the genital organs.
Next, we’re going to be talking about the two hypogastric nerves that you see here highlighted in green. Notice here on this image, this is the right hypogastric nerve while you see here highlighted on this image, the left hypogastric nerve. So, the left and right hypogastric nerves are formed when the superior hypogastric plexus splits – so as you can see here, it splits into then these two plexuses which are basically the left and right hypogastric nerves. Now, these two nerves together, they form the inferior hypogastric plexus which we are going to see right now on the next slide. So, this is the inferior hypogastric plexus. Now the terminal branches of the hypogastric nerves – as I said before – they form the inferior hypogastric nerve which is what we see now highlighted in green. Now, for information of this plexus besides the hypogastric nerves, they also contribute the, or receives contributions from the lumbar sympathetic fibers from T10 to L2 vertebrae as well as pelvic parasympathetic fibers from S2 to S4 vertebrae. This plexus gives rise to numerous branches which innervate the viscera of the pelvis and we’re going to discuss in the next slides.
So, the first one that we’re going to be highlighting here, this is known as the middle or, specifically, the left middle rectal plexus. There’s also a right one but we cannot see because we’re retracting here the rectum so we can see the left surface of the rectum and for that matter we’re seeing then specifically the left middle rectal plexus. Some of the branches of the inferior hypogastric plexus form then the middle rectal plexus which then passes to both sides of this organ, the rectum. This plexus that supplies the middle part of the rectum.
The next one that we’re going to be highlighting here, this is known as the uterovaginal plexus and this one is another plexus that arises from and communicates with the inferior hypogastric plexus and sends branches to the vagina, the uterus, ovaries and fallopian tubes.
Next, a bit further ventrally, we’re going to be seeing then the vesical plexus. As you can see, the inferior hypogastric plexus gives off several autonomic branches for the autonomic control of the pelvis viscera. The vesical plexus is another plexus from the inferior hypogastric plexus and the nerves from the vesical plexus accompany the vesical arteries and arrives at the urinary bladder as you can see here on this image. The nerves from this plexus are comprised of both sympathetic and parasympathetic fibers located on both sides of the urinary bladder then regulating the evacuation mechanism of this organ.
And, finally on this tutorial, we’re going to be highlighting these structures here, these are known as the pelvic splanchnic nerves, which are comprised of parasympathetic fibers arising from the ventral rami of spinal nerves S2 to S4. These nerves enter the sacral plexus and travel to their site corresponding inferior hypogastric plexus contributing to the autonomic innervation of the pelvis and genital organs.
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Now, good luck everyone, and I will see you next time.