Video: Lymphatics of the male genitalia

Lymph! Yes, you heard me. Lymph! It's that wildly mystical watery liquid whose name terrifies anatomy students across the world. It's actually nothing to be scared of, though. It's essentially the same thing as blood plasma found in your arteries and veins and interstitial fluid which bathes your cells in yummy nutrient-rich goodness and soaks up all the not-so-yummy cellular waste.

Lymph is this very same interstitial fluid which is drained from the capillary beds found all over our bodies. This drainage is done by lymphatic capillaries which merge and form larger vessels known as lymphatic vessels, and along those drainage highways, we have checkpoint-like structures where our immune system police, a.k.a. our lymphocytes, screen our lymph for any sneaky bad bacteria, viruses, or even metastatic cancer cells. These checkpoints are, of course, our lymph nodes.

Every organ and region of our body has its own specific drainage pattern for lymph, and today, we're quite literally going below the belt to figure out how lymph collected from the male genital region gets returned to our blood. Let's waste no time and get right into it. It's time to explore the lymphatics of the male genitalia.

To start with in this tutorial, we'll have a quick look at the male genital organs to remind us of what they are, their location, and their relationship to each other. Then we'll talk about the lymphatic system and discover the various groups of lymph nodes that are related to these male genital organs. This will include the superficial inguinal lymph nodes, the deep inguinal, the external iliac, the internal iliac, and lumbar lymph nodes. Finally, we'll be able to put it all together by looking at the drainage by organ. By doing this, we'll see the pathways that lymph takes from the male genitalia to the venous system.

Let's start by looking at the male genital organs.

The male genital organs are structures that are involved in the male reproductive system. They are structures that facilitate the production and transmission of male gametes, which we commonly know as sperm. The male reproductive system is composed of several organs as well as a number of glands and ducts. In this image, we can see a lot of these male reproductive structures. We're looking at a male pelvis from a lateral view on the right side. These are cut parts of the pelvis on the anterior side and here is the sacrum posteriorly. The urinary bladder is here anteriorly while the rectum is located more posteriorly.

The organs of the male reproductive system can be divided into two groups – an internal group and an external group. The external male genital organs include the penis and the scrotum. The internal male genital organs include the testes, epididymides, the ductus deferentes, the seminal glands, the ejaculatory ducts, the prostate, and the bulbourethral glands. We can see some of these structures in this image.

The right testis is here, within the scrotum. Sitting superior to it, we can see part of the epididymis. These two openings are part of the ductus deferens. The middle portion has been cut away to see other structures. Posterior to the bladder, we can see the right seminal gland, and inferior to the bladder, we can see part of the prostate.

We'll now switch gears and look at the anatomy of the lymphatic system.

The lymphatic system is composed of lymphoid organs and lymphoid vessels. Lymph nodes are secondary lymphoid organs which are widely distributed throughout the body. We can now see them highlighted in green in our image on the right. They are bean-shaped structures and each have at least one afferent vessel and one efferent vessel connecting it to the rest of the system. Vessels that carry lymph to a lymph node are called afferent lymph vessels and those that carry lymph away from a lymph node are called efferent lymph vessels.

Efferent lymph vessels may carry lymph to a vein, into a lymphatic duct, or even to another lymph node. This means one lymph vessel could be efferent from one lymph node and afferent to another. Eventually, all lymph ends up in the venous circulation. Lymph nodes are often found in groups, stationed throughout the body.

In today's tutorial, we will see that lymph is drained from the male genitalia into either the inguinal lymph nodes located on the proximal thigh or the pelvic lymph nodes seen here. Lymph collected by these lymph nodes will then continue to drain into another large group of nodes on the posterior abdominal wall known as the lumbar lymph nodes. From these groups of lymph nodes, the lymph of the male genitalia will travel through more lymph vessels to other sets of lymph nodes and eventually end up in the venous system. We'll identify each of these groups of lymph nodes on some images and list the components of the male genitalia that drain into them. Afterwards, we'll go through each structure of the male genitalia and show its lymphatic drainage pathway.

We'll first take a look at the superficial inguinal lymph nodes and the two tracts that make up that group.

In this anterior view of the male pelvis and the proximal lower limb, what we can see highlighted in green in this image are the inferior superficial inguinal lymph nodes. These are also known as the vertical tracts. These nodes sit along the proximal portion of this vein here, which is the great saphenous vein. Most of the lymph traveling along these nodes is from superficial lymph vessels of the lower limb, however, sometimes, they may receive some lymph drained from parts of the external genitalia and perineum.

The superior superficial inguinal lymph nodes are divided into two groups – the superomedial superficial inguinal lymph nodes seen here and the superolateral superficial inguinal lymph nodes located more laterally. Collectively, these are known as the horizontal tract of superficial inguinal lymph nodes.

The superomedial superficial inguinal lymph nodes receive lymph drained from the skin of the scrotal sac, the external genitalia, the perineum, and the anal canal. The superolateral superficial inguinal nodes, on the other hand, primarily receive lymph drained from the skin of the penis, the lower back, and lateral abdominal wall as well as the superior gluteal region.

This single lymph node is called the prepubic lymph node. It sits anterior to the superior aspect of the pubic symphysis and drains into the superficial inguinal lymph nodes that we just described.

The deep inguinal lymph nodes are a group of generally one to three lymph nodes located in the same area as the superficial inguinal nodes, just deeper as the name suggests. We can see them highlighted in green in this image now, lying medial to the femoral vein. The most superior and most constantly present of the deep inguinal lymph nodes is known as Rosenmuller's, Cloquet’s, or even Pirogoff’s node.

Lymph from the glans penis and the distal spongy urethra drains into the deep inguinal lymph nodes. Besides receiving lymph directly from these parts of the male genitalia, the deep inguinal lymph nodes also receive afferent vessels from the deep structures of the lower limb such as muscles and joints as well as from the superficial inguinal lymph nodes.

Moving on, we can now see the external iliac lymph nodes in this image, which are closely associated with the external iliac arteries and veins. These lymph nodes receive lymph directly from organs located in the anterior and superior parts of the pelvis such as the superior part of the bladder. In terms of male genitalia, the organs that drain directly into the external iliac lymph nodes are the ductus deferens, the ejaculatory ducts, part of the bulbourethral glands, the superior part of the seminal glands, the membranous urethra, most of the spongy urethra, and parts of the prostate. After reaching the external iliac lymph nodes, lymph from these structures travels to the common iliac lymph nodes which we'll discover later on in this tutorial.

The internal iliac lymph nodes are our next node group of interest. True to their name, these lymph nodes drain the area which is supplied by the internal iliac artery and its branches. The internal iliac lymph nodes can be further divided into three subdivisions which include the superior gluteal lymph nodes, the inferior gluteal lymph nodes, and the lateral sacral lymph nodes. The parts of the male genitalia that drain into the internal iliac nodes are the prostate, the prostatic urethra, the membranous urethra, the proximal portion of the spongy urethra, part of the bulbourethral glands, and the inferior part of the seminal glands.

Just like the external and internal iliac arteries and veins have a related common iliac structure, the lymphatic system has that too. These are the common iliac lymph nodes, sitting around the common iliac artery. The common iliac lymph nodes collect lymph from both the internal and external iliac nodes. In addition to that, just like the common iliac artery is the root artery for all arteries of the lower limbs and most pelvic organs, the common iliac lymph nodes similarly receive lymph drained from these regions too.

The medial members of the common iliac lymph nodes are the ones highlighted in this image, which are known as the promontorial lymph nodes, or you may even see them referred to as the subaortic lymph nodes – if that's not enough names for you. The name comes from their location being anterior to the sacral promontory.

Inferior to the promontorial nodes are another group of nodes known as the medial sacral nodes, which are found along the length of the median sacral artery.

The last group of lymph nodes that receives lymph directly from the organs in the male genitalia are the lumbar lymph nodes which we can see here highlighted in green. The lymph nodes receive lymph directly from the testes and the epididymis. This may seem a bit strange, but if you think back to embryology, it should make sense. The testes descend from the posterior abdominal wall, and while doing so, bring all vessels with them. So just as the arteries and veins come and go to this area, so do the lymphatic vessels.

The lumbar lymph nodes can be divided into several different groups. On the left side, we have the left lumbar lymph nodes which can be further divided into the lateral aortic, the preaortic as well as the retroaortic lymph nodes which are located posterior to the aorta and not visible in this illustration. Between the aorta and the inferior vena cava, we have the intermediate lumbar lymph nodes which are also very appropriately known as the interaorticocaval lymph nodes. Finally, on the right, we have the right lumbar lymph nodes which consists of the precaval, the lateral caval, and the retrocaval lymph nodes.

We've looked at the first group of lymph nodes that drain the various organs, glands, and ducts of the male genitalia, so now we'll flip things around and look at the pathway lymph takes from each component of the male genitalia. Here's the order that we'll go through – the testes and epididymis, the scrotum, the ductus deferentes, the seminal glands, the ejaculatory ducts, the prostate, the bulbourethral glands, the penis, and finally, the three parts of the urethra.

The testes and epididymis drain differently than most of the rest of the male genitalia due to their embryological origin. The lymph from the testes and the epididymis follow the testicular veins towards the lumbar region. Within the group of lumbar lymph nodes, lymph from the right testis and epididymis drains to a different subgroup than lymph from the left testis and epididymis. The right testis and epididymis drains to the furthest right subgroup of the lumbar lymph nodes called the right lumbar lymph nodes. These lymph nodes are just next to where the right testicular vein meets the inferior vena cava so it makes sense that lymph from the right testis will drain here. Lymph from the left testis and epididymis follows the left testicular vein to the left lumbar lymph nodes. These lymph nodes are located to the left of the abdominal aorta next to the left testicular vein.

Next, we'll have a look at the scrotum. Lymph from the scrotum stays superficial in the skin and travels to the superomedial inguinal lymph nodes. Parts of the posterior scrotum can also drain into the inferior superficial inguinal lymph nodes.

So as I'm sure you've now noticed, even though the scrotum is the skin that surrounds and holds the testes, it has a completely different lymphatic drainage pathway. This is because of the different origins of these two structures. Since the scrotum was always continuous with the skin of this area, its lymphatic drainage follows in pattern with other structures in that area. It's the embryological descent of the testes that results in the different lymphatic drainage of these organs.

The ductus deferentes, or the vas deferentes as it used to be known as, are next on our list. Afferent lymph vessels from the proximal portion of each ductus deferens generally ascends with the lymph vessels of the testes to the lumbar lymph nodes. Lymph drained from the intermediate and terminal portion of the ductus deferentes, however, mostly drains into the external iliac lymph nodes.

Next up are the seminal glands. The lymphatic drainage of these glands is split. The superior part of the seminal gland has a different drainage than the inferior part. The superior part of the seminal glands first drains through the same place as the ductus deferens, which is the external iliac lymph nodes. Lymph from the inferior part of the seminal glands, however, first drain into the internal iliac lymph nodes.

Moving along, we'll now look at the ejaculatory ducts, which are found posterior to the neck of the bladder. They are formed by the joining of the ductus deferens and the duct of the seminal gland. The lymphatic drainage of these structures is nice and straightforward. Lymph from the ejaculatory ducts first drains into the external iliac lymph nodes.

We're about halfway through the organs now and next up is the prostate. Lymph from the prostate gland closely follows its venous drainage pathway. The posterior lobe of the prostate gland is drained via three primary pathways: A lateral pathway which drains to the external iliac lymph nodes – these lymph vessels also drain the terminal portion of the ductus deferens and the seminal glands; a laterodorsal pathway which drains into the internal iliac nodes via a course following the prostatic artery; and finally, a dorsal pathway which drains to the sacral and promontorial lymph nodes.

Lymph drained from the anterior lobe of the prostate can be traced via two routes. The majority of lymph drained from the anterior surface proceeds to the external iliac lymph nodes via the paravesical space. Alternatively, some vessels from the anterior lobe leave the prostate from the posterior surface draining into a group of nodes known as the inferior gluteal nodes which are part of the internal iliac nodes. Important to note is that many of the lymph vessels of the prostate anastomose with their counterparts of several neighboring organs; for example, of the urinary bladder and the rectum. This can have important clinical implications which we will discover later in this tutorial.

The bulbourethral glands are what we'll look at next. These small glands are found just inferior to the prostate, as we can see in this image of a coronal section through part of the male pelvis. Lymph from the bulbourethral glands travel to two groups of lymph nodes – the internal iliac lymph nodes as well as the external iliac lymph nodes.

The various parts of the penis have different lymph drainage pathways. We'll look at the skin, the cavernous bodies, and the glans penis. Firstly, the skin of the penis drains into the superficial inguinal lymph nodes. This makes sense since the skin is the most superficial component. Lymph drained from the glans and the cavernous bodies of the penis primarily tends to drain into the superomedial superficial lymph nodes; however, structures are also known to have some efferent lymph vessels which terminate at the deep inguinal lymph nodes.

The final part of the male genitalia is the urethra, which we’ll look at now. The urethra is divided into three parts – the prostatic urethra, the membranous urethra, and the spongy urethra. Let’s start with the prostatic urethra.

Since this part of the urethra is within the prostate gland, lymph from the prostatic urethra follows one of the same parts. It drains to the internal iliac lymph nodes. Lymph from the membranous urethra and the most proximal portion of the spongy urethra may drain into a number of destinations, namely, the external iliac nodes and the inferior gluteal nodes which are part of the internal iliac nodes. The distal part of the spongy urethra, though, follows the lymphatic drainage of the glans penis and primarily drains into the superomedial superficial inguinal lymph nodes, sometimes via the prepubic lymph node. And just like the glans penis, the afferent vessels of the distal spongy urethra may also sometimes drain into the deep inguinal lymph nodes.

So now that we've identified the first group of lymph nodes that drain each of the components of the male genitalia, what happens from there? We'll now look at the overall pathway that lymph takes to get from the male genitalia all the way to the venous system.

Of the lymph nodes that drain the male genitalia, lymph in the superficial inguinal lymph nodes has the furthest distance to travel. First, lymph travels to the deep inguinal lymph nodes which have also received lymph from other organs and parts of the body as we identified earlier. From there, lymph travels to the external and internal iliac lymph nodes. Next, it continues to follow the venous drainage pathway and heads for the common iliac lymph nodes. Lymph continues superiorly to the lumbar lymph nodes.

The lumbar lymph nodes are the final group of lymph nodes that lymph from the male genitalia travels through. From the lumbar lymph nodes, efferent lymphatic vessels carry lymph to the cisterna chyli, which we can see highlighted in green on this image.

The cisterna chyli is the inferior dilated portion of the longest lymphatic vessel in the body – the thoracic duct – which we can now see highlighted in green. This is the last portion of the lymphatic system that lymph from the male genitalia travels through. It runs superiorly through the thorax and enters the venous system at the left venous angle. The left venous angle is where the left internal jugular vein and the left subclavian vein meets to form the left brachiocephalic vein. At this point, the left venous angle and the thoracic duct join the venous system and lymph enters the venous circulation.

So that covers it for the anatomy portion of the lymphatics of the male genitalia. We'll now have a quick look at a clinical note associated with the topic.

A key clinical component of the lymphatics of the pelvis is that the lymph nodes are highly interconnected. This means that the lymph drainage can travel in many directions, but also that metastatic cancer can spread easily throughout the pelvis using the lymphatic pathways. For example, if a male has prostatic cancer, we know from this tutorial that cancer cells will likely first travel to either the internal or external iliac lymph nodes since that's where lymph from the prostate primarily drains to. From the internal and external iliac lymph nodes, the cancer cells can continue to the common iliac lymph nodes and beyond.

Knowledge of the lymphatics of any organ is very important in both the staging and treatment of cancer. As malignant cells spread or metastasize from their primary tumor, they often do so via the lymphatic system and usually proceed in a sequential order just like what I just mentioned. Hypothetically, the sentinel lymph node is the first lymph node or a group of lymph nodes draining a cancer such as these circled here. It is also the first place where cancer cells are most likely to spread.

Using a technique known as the sentinel lymph node biopsy, doctors can examine as to where the cancerous cells from a primary tumor have spread or metastasized to other parts. This is done by using special dyes injected into a tumor and these nodes can be identified and tested to see if the cancer has spread. If there is a tumor in the prostate, it may metastasize to surrounding lymph nodes, interfering with the flow of lymphatic fluid through the node and may even block the related lymph vessels.

Well done! You made it through the tutorial. You're now an expert on lymphatics of the male genitalia. Let's have a quick review of what we looked at today.

We looked at the five main groups of lymph nodes that lymph from the male genitalia first drain to. These are the superficial inguinal lymph nodes, the deep inguinal lymph nodes, the external iliac lymph nodes, the internal iliac lymph nodes, and finally, the lumbar lymph nodes.

The superficial inguinal nodes are divided into superomedial, superolateral, and inferior superficial inguinal lymph nodes. These nodes receive lymph in afferent vessels from the skin of the scrotal sac, the perineum, the skin of the penis, the cavernous bodies of the penis, the glans penis, and the distal spongy urethra. Lymph then travels from the superficial inguinal nodes to the deep inguinal lymph nodes.

The deep inguinal lymph nodes don't receive too much lymph directly from the male genitalia. Here's what they do get from some of these structures – sometimes, lymph from the glans penis and distal spongy urethra. They also receive lymph from the superficial inguinal lymph nodes. Lymph then travels from the deep inguinal nodes to the external iliac lymph nodes.

Next up are the external iliac nodes, which are a bit of a longer list. They receive lymph from the intermediate and terminal portion of the ductus deferentes, the ejaculatory ducts, part of the bulbourethral glands, the superior part of the seminal glands, the membranous urethra, the proximal spongy urethra, and part of the prostate. They also receive lymph from the deep inguinal lymph nodes. Lymph then travels from the external iliac nodes to the common iliac lymph nodes.

Next up are the internal iliac nodes. They receive lymph from parts of the prostate, the prostatic urethra, the membranous urethra, the proximal spongy urethra, part of the bulbourethral glands, and the inferior part of the seminal glands. Lymph then travels from the internal iliac nodes to the common iliac lymph nodes along with the external iliac lymph nodes.

Finally, the last major group draining the male genitalia are the lumbar lymph nodes. They drain lymph from the testes, the epididymis, and the proximal portion of the ductus deferentes. They also receive afferent vessels from the common iliac lymph nodes. Lymph then travels from the lumbar nodes to the cisterna chyli.

To wrap up this tutorial, we looked at the cancer metastasis and how easily those cells can travel through the pelvis by using the highly interconnected lymphatic system.

That brings us to the end of our tutorial on the lymphatics of the male genitalia. I hope you enjoyed it. Thanks for joining me and happy studying.