Nerves and lymphatics of the pelvis
Definitions & Key takeaways
The pelvis is the lower part of the trunk of the body, located between the abdomen and the legs. It has several important nerves that innervate various structures; and a network of lymphatic vessels and lymph nodes.
The nerves of the pelvis are divided into somatic and autonomic nerves. Somatic nerves arise from the lumbosacral and coccygeal plexus, and include the obturator, sciatic, superior gluteal, inferior gluteal, pudendal, nerve to piriformis, nerve to quadratus femoris, nerve to obturator internus, nerves to levator ani and coccygeus, and the posterior cutaneous nerve of the thigh.
Autonomic nerves of the pelvis include the sacral sympathetic trunks, which supply the lower limb. These include the periarterial plexuses, which supply motor fibers to the superior rectal, ovarian, and internal iliac arteries and their branches; the hypogastric plexuses, the main origin of sympathetic fibers in the pelvis; and pelvic splanchnic nerves, which are the main origin of parasympathetic fibers in the pelvis. There are also visceral afferent fibers that receive sensory information from the pelvic viscera.
The lymphatic drainage of the pelvis consists of major and minor lymph nodes. Major lymph nodes include the superficial and deep inguinal, internal iliac, external iliac, sacral, and common iliac lymph nodes; whereas minor lymph nodes lie in the connective tissue that surrounds branches of the internal iliac blood vessels.
Introduction0:00–0:32
The neurovascular structures of the pelvis include nerves, arteries, veins, and lymph nodes. These structures lie on the posterolateral walls of the pelvic cavity.
Generally the somatic nerves are the most lateral, arteries lie medial to nerves, and veins lie between these two. Lymph nodes are usually clustered around the veins, and lymph vessels that come off these nodes ascend parallel to the veins.
Now, let's take a closer look at the lymphatics and nerves of the pelvis specifically. Let’s talk about the lymphatic drainage of the pelvis, which follows various major and minor groups of lymph nodes.
Lymphatic drainage0:32–0:56
These lymph nodes have variable, sizes, numbers, and locations, and the lymph node clusters’ names are based on the adjacent structures and nearby blood supply.
Furthermore, these nodes are all interconnected, so their drainage often overlaps and can vary quite a bit. First, there are the inguinal lymph nodes which lie around the inguinal ligament, and they’re divided into superficial and deep inguinal lymph nodes.
Inguinal lymph nodes0:56–1:47
The superficial inguinal lymph nodes receive lymphatic drainage from the superficial lower limb, abdominal wall inferior to the umbilicus, gluteal region and superficial perineal structures such as the distal vagina, vulva and scrotum, and typically drain into the external iliac lymph nodes.
The deep inguinal lymph nodes receive lymph from the superficial inguinal nodes, as well as the deep portions of the lower limb, the glans clitoris in females or glans penis in males and the distal spongy urethra.
External iliac lymph nodes 1:47–2:12
Finally, the external iliac lymph nodes drain lymph into the common iliac lymph nodes, which lie around the common iliac arteryNext are the internal iliac lymph nodes, which lie along the anterior and posterior divisions of the internal iliac artery.
Internal iliac lymph nodes2:12–2:38
Sacral lymph nodes2:38–3:02
Then, they drain into the internal iliac lymph nodes or the common iliac lymph nodes. Finally, there are the common iliac lymph nodes, which lie along the common iliac blood vessels.
Common iliac lymph nodes3:02–3:30
These lymph nodes receive lymph from the external iliac, internal iliac, and sacral lymph nodes. Part of some pelvic viscera, like the neck of the urinary bladder and the inferior part of the vagina, may bypass their other sets of nodes and drain their lymph directly into the common iliac lymph nodes.
From the common iliac lymph nodes, lymph goes to the lumbar lymph nodes, which are also called caval or aortic lymph nodes.
Lumbar and pelvic lymph nodes3:30–3:59
These lymph nodes lie in the connective tissue that surrounds branches of the internal iliac blood vessels. Alright, before we look at pelvic nerves, feel free to pause the video and see if you can name the main lymph node groups of the pelvis!
QuizQuiz3:59–4:12
Innervation4:12–4:48
Okay, now, let’s switch gears and look at the nerves of the pelvis, which can be divided in somatic and autonomic nerves.
Somatic nerves arise from the lumbosacral and coccygeal plexus. These include the obturator nerve, the lumbosacral trunk, and spinal nerves that arise from the sacral and coccygeal segments of the spinal cord.
Sacral and coccygeal spinal nerves interconnect to form an extensive network of nerves called the sacral and coccygeal nerve plexuses, which lie on the piriformis and coccygeus muscles.Let’s start with the obturator nerve, which arises from the lumbar plexus - specifically, the anterior rami of the second, third, and fourth lumbar spinal nerves.
Obturator nerve4:48–5:28
This nerve enters the lesser pelvis and runs along the lateral wall of the pelvis to the obturator canal, which is an opening within the obturator membrane.After entering the obturator canal, the obturator nerve divides into anterior and posterior branches, which actually don’t supply any structures within the pelvis.
Instead, these branches enter the thigh and supply the adductor muscles of the medial thigh.Now, right above the pelvic brim, the descending part of the fourth lumbar nerve unites with the anterior ramus of the fifth lumbar nerve, forming the lumbosacral trunk.
Lumbosacral trunk5:28–9:27
This trunk descends on the anterior surface of the ala of the sacrum, and it unites with the sacral plexus, forming the lumbosacral plexus.
So the lumbosacral plexus is formed by the anterior rami of spinal nerves L4 to S4. This plexus lies on the posterolateral wall of the lesser pelvis, and it gives off a number of branches for pelvic and lower limb structures.The first of these branches is the sciatic nerve, which is the largest nerve of the human body.
This nerve arises from the anterior rami of spinal nerves L4 to S3. Then, it passes through the greater sciatic foramen, typically below the piriformis muscle, and enters the gluteal region.
Finally, it descends on the posterior aspect of the thigh and gives branches that supply the hip joint, posterior muscles of the thigh, and all the muscles of the leg and foot.
Second, there’s the pudendal nerve, which arises from spinal nerves S2, S3 and S4. After it forms, the pudendal nerve leaves the pelvis through the greater sciatic foramen, between the piriformis and coccygeus muscles.
Then, it winds around the ischial spine and the sacrospinous ligament. Finally, it passes through the lesser sciatic foramen and enters the perineum to provide sensory information to the external genitalia as well muscular branches to perineal muscles.
Two other branches of the lumbosacral plexus are the superior gluteal and inferior gluteal nerves. The superior gluteal nerve arises from L4, L5, and S1.
This nerve leaves the pelvis above the piriformis muscle, and it passes through the greater sciatic foramen to supply the gluteus medius and gluteus minimus muscles in the gluteal region.
Finally, the inferior gluteal nerve, which arises from L5, S1, and S2. This nerve also leaves the pelvis through the greater sciatic foramen, but below the piriformis muscle.
The inferior gluteal nerve supplies the gluteus maximus, which is the largest muscle of the gluteal region and, in fact, the entire body!Here’s a memory trick!
The relations of these nerves to the piriformis muscle correspond to their names. The superior gluteal nerve passes above the piriformis, and the inferior gluteal nerve passes below the piriformis.
Okay, next, the lumbosacral plexus gives off five nerves that are easy to memorize, because their name is the name of the muscle they innervate.
First, there’s the nerve to quadratus femoris, which arises from L4, L5, and S1 and supplies the quadratus femoris and inferior gemellus muscles.
Second, there’s the nerve to obturator internus, which arises from L5, S1, and S2 and supplies the obturator internus and superior gemellus muscles.
Third, there’s the nerve to piriformis, which arises from S1 and S2 and supplies the piriformis muscle. And the last two of these easy to remember branches are the nerves to the levator ani and coccygeus, which arise from S3 and S4 and supply the levator ani and coccygeus muscles.
Finally, the sacral plexus gives off the posterior cutaneous nerve of the thigh and perforating cutaneous branches. And we’re saying just the sacral plexus here, because only sacral nerves S1 to S4 contribute to these branches.
Sacral plexus9:27–10:09
So the posterior cutaneous nerve of the thigh arises from S1 to S3 and supplies cutaneous branches to the buttocks and the uppermost medial and posterior sides of the thigh.
The perforating cutaneous branches, on the other hand, arise from S3 and S4 to supply the skin covering the medial side of the buttocks.Okay, now we’re just going to quickly go over the other 24 branches of the sacral… just kidding!!
QuizQuiz10:09–10:32
Instead, you can take a quick break and see if you can recognize the sciatic, pudendal, superior and inferior gluteal nerves on this image.
Coccygeal plexus10:32–11:07
And now, just a few words about the coccygeal plexus, which lies on the pelvic surface of the coccygeus muscle. This plexus is formed by the anterior rami of S4, S5, and the coccygeal spinal nerves.
Branches of this plexus supply the coccygeus and levator ani muscles, and the sacrococcygeal joint. This plexus also gives the anococcygeal nerve, which pierces the anococcygeal ligament to supply a small area of skin between the tip of the coccyx and the anus.
And finally, let’s look at the autonomic nerves of the pelvis, which include sympathetic and parasympathetic nerves. Let’s start off with the sympathetic nerves that reach the pelvic cavity through the sacral sympathetic trunks, periarterial plexuses, and hypogastric plexuses.
Sympathetic nerves11:07–11:28
First, there are the sacral sympathetic trunks, which continue the lumbar sympathetic trunks inferiorly, and typically consist of four sympathetic ganglia.
Sacral sympathetic trunks11:28–12:15
These trunks also send small branches that supply the inferior hypogastric plexus and the median sacral artery. The main function of these branches is to provide sympathetic innervation to the lower limb.
Finally, the distal portion of these trunks converge anterior to the coccyx to form a small ganglion called the median ganglion impar, or the coccygeal ganglion.
Next are the periarterial plexuses, which provide sympathetic fibers for the ovarian, superior rectal, and internal iliac arteries and their branches.
Periarterial plexuses12:15–12:34
These sympathetic fibers cause vasoconstriction, which means they make blood vessels narrow. Then there are the superior and inferior hypogastric plexuses, which provide autonomic innervation to the pelvic cavity, and receive afferent impulses from the pelvic viscera.
Hypogastric plexuses12:34–13:40
Now, the main part of the superior hypogastric plexus actually continues from another plexus called the intermesenteric plexus.
The superior hypogastric plexus receives sympathetic fibers from the intermesenteric plexus by L3 and L4 splanchnic nerves.
The superior hypogastric plexus , and it lies inferior to the bifurcation of the aorta, descends and enters the pelvis, and then it divides into the right and left hypogastric nerves, which run along the anterior surface of the sacrum, and eventually end up lateral to the rectum.
Finally, the right and left hypogastric nerves merge with the pelvic splanchnic nerves and spread in a fan like fashion to form the right and left inferior hypogastric plexuses, which contain sympathetic, parasympathetic and visceral afferent fibers to innervate the pelvic viscera.Finally, there are the parasympathetic nerves, called the pelvic splanchnic nerves, which arise from the anterior rami of spinal nerves S2-S4.
Parasympathetic nerves13:40–14:17
These nerves carry preganglionic parasympathetic fibers from spinal cord segments S2-S4 to the inferior hypogastric plexuses, which carry these fibers to various pelvic viscera.
Also, the pelvic splanchnic nerves carry visceral afferent fibers from pelvic viscera to the sensory spinal ganglia of spinal nerves S2-S4.Now, each part of the autonomic nervous system serves a bunch of roles in the pelvis.
Functions of autonomic nerves in the pelvis14:17–15:02
The sympathetic innervation of the hypogastric and pelvic plexuses inhibits peristaltic contraction of the rectum, and it also stimulates the contraction of internal genital organs during orgasm, which results in ejaculation.
The parasympathetic system, on the other hand, stimulates the contraction of the rectum for defecation and that of the bladder for urination.
Also, there are a group of parasympathetic fibers in a plexus found on the surface of the prostate gland, called the prostatic plexus.
These fibers penetrate the pelvic floor and innervate the external genitalia, which causes erection. Finally, there are the afferent visceral fibers, which receive sensory impulses from the pelvic viscera and typically travel with the parasympathetic fibers via the inferior hypogastric plexus and pelvic splanchnic nerves of S2-S4.
Afferent visceral fibers15:02–17:07
However, the course and the destination of these sensory fibers differ, and this depends on whether these fibers are sensing superior or inferior to an imaginary line called the pelvic pain line.
This line corresponds to the inferior limit of the peritoneum that extends into the pelvic cavity, and pelvic organs can be either superior or inferior to this line.
Superior organs include the abdominopelvic organs that lie within the peritoneum or are in contact with the peritoneum, like the kidneys, the ureters, superior part of the bladder, and the upper part of the uterus.
Inferior organs include the organs that lie inferior to the peritoneum, like the rectum, cervix, and vagina. Of note, the pelvic pain line does not correlate with the peritoneum in the large intestine, and it goes through the middle of the sigmoid colon.
So, pain sensation that comes from superior organs follows along the sympathetic nerves in a retrograde fashion, travelling up the hypogastric and aortic plexuses.
Then, they are carried by the abdominopelvic splanchnic nerves to the lumbar sympathetic trunks and white rami communicantes.
Finally, they reach the cell bodies in the inferior thoracic and upper lumbar spinal ganglia. Pain sensation that comes from the inferior organs also travels in a retrograde fashion, but this time along parasympathetic nerves.
These sensations pass through the pelvic and inferior hypogastric plexuses to reach the cell bodies of the spinal sensory ganglia of S2-S4.
Alright, as a quick recap, lymphatic drainage of the pelvis includes major and minor lymph nodes. Major groups of lymph nodes include the superficial and deep inguinal, internal iliac, external iliac, sacral, and common iliac lymph nodes.
Review17:07–18:42
The nerves of the pelvis can be divided in somatic and autonomic nerves. Somatic nerves arise from the lumbosacral and coccygeal plexus, and they are the obturator, sciatic, superior gluteal, inferior gluteal, pudendal, nerve to piriformis, nerve to quadratus femoris, nerve to obturator internus, nerves to levator ani and coccygeus, and the posterior cutaneous nerve of the thigh.
Autonomic nerves of the pelvis include the sacral sympathetic trunks, which supply the lower limb; periarterial plexuses, which supply motor fibers to the superior rectal, ovarian, and internal iliac arteries, and their branches; the hypogastric plexuses, which are the main origin of sympathetic fibers in the pelvis; and pelvic splanchnic nerves, which are the main origin of parasympathetic fibers in the pelvis.
There are also visceral afferent fibers which receive sensory information from the pelvic viscera. Above the pelvic pain line, these fibers travel with sympathetic fibers, and below the pelvic pain line they travel with the
Nerves and Lymphatics of the Pelvis
Figure 1. A. Anterior view of the lymph nodes in a biologically female pelvis. B. Midsagittal view of a biologically female pelvis showing the lymphatic drainage of the pelvis and perineum.
Figure 2. Anterolateral view of a biologically female pelvis showing the nerves of the pelvis.
Figure 3. A. Anterior view of the somatic nerves of the pelvis. B. Posterior view of the course of the gluteal nerves.
Figure 4. Anterior view of the autonomic nerves of the pelvis.
Unlabelled diagrams
- "Gray's Anatomy" Churchill Livingstone (2015)
- "Textbook of Anatomy Abdomen and Lower Limb;" Elsevier Health Sciences (2014)
- "McMinn's Clinical Atlas of Human Anatomy" Elsevier Health Sciences (2008)
- "General Anatomy" McGraw-Hill Europe (2007)
- "Clinically Oriented Anatomy" Lippincott Williams & Wilkins (2013)
- "Last's Anatomy e-Book" Elsevier Health Sciences (2011)
- "Clinically Oriented Anatomy" Lippincott Williams & Wilkins (2008)
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