Transcription
Hey guys, how are you doing today? I'm so excited because now we're going to talk about anatomy of the lymph node. I have watched many videos online. I can assure you this is gonna be the best. This is Medicos is Perfection. Ellis, we make medicine so easy that even a child can understand it.
[Music]
Here is where I get my info. These books are the best for Anatomy. Check the links in the description. The previous video, we have discussed the lymphatic system. You should watch that video before this one. I've asked you this question on the previous video, so here are the answers. Just remember that this is called the right Venus angle, left Venus angle. The lymphatic vessels will drain here, the right lymphatic duct, and here into the thoracic duct. Both of them will land into these angles. Then the right brachiocephalic and left brachiocephalic veins, they joined together to form the superior vena cava going to the right atrium of the heart.
So what are these lymph nodes? They are kidney-shaped, small, encapsulated bodies located along the course of the lymph vessels. As I've told you before, they contain cells of the immune system such as lymphocytes and macrophages. Vacancies of outer cortex and an inner medulla. The cortex has the lymph follicles, the medulla does not. The cortex receives lymph from the afferent vessels. The middle of forms sinuses which will lead to the hilum leading to the efferent vessel.
Let's get practical and talk clinical. Lymph nodes are filters interrupting the lymphatic vessels. The flow is slow in the lymph node, so cells that metastasize from primary tumor sites, they will enter the lymphatic vessels, especially carcinomas because they love the lymph. They will end up where? In the lymph node. It's slow, so it will grow forming a lymphoma. Enlarged lymph node that's not tender. On the other hand, lymph nodes that drain infected sites leading to lymphadenitis. These lymph nodes are tender. So in both cases, whether cancer or infection, the lymph node aden is enlarged. However, in lymphoma, it's not painful to touch, while in infection, it is tender. Lymph nodes can become diffusely enlarged in systemic illnesses such as viral infection.
What's the purpose of lymph nodes? They are centers for antigen presentation, lymphocyte activation, differentiation, and proliferation because the lymphocytes, they start as naive cells. This naive cells need to grow up and mature. How do they grow up? By recognizing the antigen. When they recognize the antigen, they mature, they develop memory cells, and everything works fine. So they generate mature, antigen-primed B and T-lymphocytes. Your body has approximately 450 lymph nodes. The highest concentration of lymph nodes is near the viscera, especially the mesenteries. By the way, how many bones do you have? The answer is 206. How many muscles do you have? And the answer is around 600.
Many students get confused when we talk about stroma and perineum. It's so easy. Stroma is the connective tissue matrix. It's the structure. It's the foundation on which we're gonna lay the parenchyma. So here is the stroma and here is the parenchyma. Stroma provides structure that holds the cell of the parenchyma together. It has no specific function to that specific organ, which means the stroma of the lymph node has nothing to do with fighting pathogens. This is the job of the parenchyma. Stroma consists of an outer fibrous capsule, and this fibrous capsule is gonna extend some trabeculae to divide and conquer the lymph nodes. Also, it has sinuses which will lead to hilum. What are sinuses? They are lymphatic channels. What is the hilum? It's the exit of the lymph node.
The parenchyma on the other hand is the bulk of a substance. Literally means visceral flesh, while stroma literally mean bed. The parenchyma is the functional part, while the stroma is the structural part. For instance, in the brain, world is the parenchyma, is the neurons and the glial cells, the actual cells. In the lungs, they are the alveoli, again, the functioning units.
Now let's go to the hard stuff. So here we have the nice lymph nodes again. Afferent lymphatic vessels, efferent lymphatic vessels. Aff to from, perfect. Then we have the fibrous capsule here, extending trabeculae that divide the lymph nodes into sections. And here we have the main thing, which is the lymphoid follicle. They start as primary lymphoid follicle, then they will grow up and develop a germinal Center, and then we call them secondary lymphoid follicles because they have this germinal Center. Very cool. We divide it in two cortex, which is here, medulla, which is here, and a para cortex in between. Here medullary sinus is the last part leading to the hilum. Here comes the artery and vein. They bring lymphocytes and macrophages from the bloodstream to the lymph stream. This part is called the high endothelial venule, very important. Again, outer cortex, inner medulla, para cortex in between. The cortex contains the B lymphocytes. Para cortex T lymphocytes. How about the inner medulla? Plasma cells, which are the B lymphocytes when they mature and become antigen-secreting B lymphocytes. Here the medullary sinuses contain macrophages.
Let's go to the follicles. They start as naive primary follicles. They start to mature and grow up and develop a germinal Center in the middle of the terminal Center. This German center will displace and marginalize some cells to the margin, creating something in the middle called the mantle. Repetition makes perfection. Here is your secondary follicle, germinal center, then the mantle, then the margin. All of this is in the cortex. Then we have para cortex, middle or medullary sinus. Cortex has the B-cells, para cortex T-cells, medulla plasma cells, middle area sinuses, macrophages. Perfect.
So B lymphocytes vs T lymphocytes in the lymph nodes. We find B cells in the cortex, T cells in the pair quarters. In this plane, especially in the white pulp. P lymphocytes are in the peripheral areas. T lymphocytes in the peri arterial or lymphatic sheath. If you can notice, T lymphocyte is always in a P in the para cortex or in the peri arterial or whatever. Each organ in your body will drain into the local lymph nodes. So if we can study these structures and where do they drain, we can tell if these lymph nodes are enlarged, what kind of organs may be involved. So for instance, if you have breast cancer, axillary lymph nodes may be involved. That's why a physical exam of the breast always includes the axillary lymph nodes.
Lymphatic drainage. All of your body drains into the amazing glorious thoracic duct, except for the upper right quadrant, which drains into the right lymphatic duct. Both of them will drain into the superior vena cava towards the right atrium.
Let's do some clinical correlation. Cancer spreads either by contiguity, which means to the local structure, or metastasis, which means to distance structures. Lymphoma, which is a type cancer, can spread by either continuity, such as Hodgkin's lymphoma, or metastasis, such as non-Hodgkin's lymphoma. Carcinomas love to go to the lymph. Sarcomas, they like to go to the blood, especially veins, because they are weaker. Since they go to veins, they will land in the liver or in the lungs. That's why most common locations of secondary sarcomas are lungs and liver. Makes perfect sense. Cancer in the lymph node could be primary or secondary. You need a biopsy to tell. To biopsy a lymph node, never use a fine needle aspiration. You need either an excisional biopsy or a core needle biopsy.
Stay tuned for the next video. We're gonna talk lymph. Your feedback means the whole world to me, so let me know below in the comment section. Please subscribe and hit the bell to get notified. I'll like to see on Facebook as well as all of these platforms. Please consider supporting this channel on Patreon. This is Medical Superficialis. Be safe, stay happy, and study hard.