 Hey everybody, Dr. O'Hare, we're primarily going to talk about the lymphatic vessels and lymph in this video, but first I want to talk about one thing. We always talk about the lymphatic and immune systems together, just like, you know, chapters and anatomy textbooks do, but what is the difference between the two? So here's how I look at it. The lymphatic system is the system that carries lymph, that carries this fluid, and as it carries it, it filters it. So that's the job of the lymphatic system. And it shows what it's filtered out of your lymphatic fluid to your immune system. The immune system is the cells and organs and structures whose job it is to recognize what's in that filtered out material and neutralize or destroy any pathogens that are there. So the two work together, but we're going to focus on the lymphatic system here. So here you see the lymphatic system. First of all, let me show you where does lymph come from? We've covered this back in the last unit, but lymph is the excess fluid that's filtered out of your capillary beds that's not reabsorbed. So we talked about there being about 3.6 liters of that fluid a day. So when this fluid leaves your capillaries, it's now called interstitial fluid, the fluid between your cells. Once it's entered a lymphatic capillary, a lymphatic vessel, it's now called lymph. So you can see here on the right-hand side in this image, it actually enters through what are called endothelial flaps. So we consider them valves because they prevent the backflow of fluid. So once this fluid enters a lymphatic vessel, it is now in your lymphatic system. Now this is not a circulatory system. There's no pump like the heart and it doesn't pump away from your heart and back towards all of these lymphatic vessels. Let me go ahead and show you again. All of these lymphatic vessels start at the extremities and they work towards the heart. So they're all traveling in one direction. So this fluid that is now trapped in lymphatic system only has one way to go and it's going to travel towards your abdominal pelvic cavity and towards your heart. But the good thing about that is dispersed throughout your body are 500 to 600 lymph nodes. So I think about them like checkpoints. So there's 500 to 600 checkpoints that this fluid has to go through. And the job of your lymph nodes is to filter out 99% of what's traveling through it and then also look for pathogens, look for invaders that it should show to the immune system. All right. So that's the lymphatic system, the lymphatic fluid and the lymphatic vessels. There are only two named vessels I'll ask you to know. So as you can see, you have an entire system. It's all working towards your heart. But the only two I'll ask you to know are going to be at the end too, that the great vessels that receive all this lymphatic fluid and you can see them both here. The right lymphatic duct is going to receive all the lymph from the right side of your head, your right arm and your right thoracic cavity. So the upper right portion of your body. The thoracic duct is going to receive all the lymphatic fluid from everywhere else. Okay. So that's a quick introduction to the lymphatic and immune systems as well as talking about where lymph comes from, where it goes and how it gets there. I hope this helps. Have a wonderful day. Be blessed.