In this video, we're going to compare the cardiovascular system to the lymphatic system as we complete this table behind me. And so notice that the left hand side of the table is all about the cardiovascular system, which we covered in great detail in previous lesson videos. So this is mostly review, and the right hand side of the table is all about the lymphatic system, which is the main focus of these videos. Now recall from previous lesson videos that the cardiovascular system vasculature forms a circulatory network or a loop since arteries carry blood away from the heart, and veins carry blood back towards the heart. However, the lymphatic system vasculature is not a circulatory network or a loop. Instead, it is going to be more linear or blind-ended with a definitive beginning at the lymphatic capillaries and a definitive end at the lymphatic ducts. And so if we take a look at our images down below, we can actually see this and notice that on the left hand side, we've got the same image that we've seen many times before showing the circulatory network or the loop of the cardiovascular system, and the right hand side is showing the linear or blind-ended vasculature of the lymphatic system that, again, has a definitive beginning at the lymphatic capillaries and a definitive end at the lymphatic ducts.
Now the cardiovascular system, of course, is going to transport blood, which is a red and viscous or thick fluid, whereas the lymphatic system is going to transport lymph, which is a clear and colorless fluid. Now the cardiovascular system is going to be functionally optimized for nutrient and gas exchanges, such as oxygen and carbon dioxide gas exchanges, whereas the lymphatic system is going to be functionally optimized for returning lost or leaked fluids and proteins from the cardiovascular system back to the cardiovascular system to maintain fluid balance. And the lymphatic system is also functionally optimized for immune surveillance and response.
Now the cardiovascular system is going to have the heart, which we know acts as a pump to propel blood throughout the entire cardiovascular system. And the heart, which serves as a pump, creates a relatively high pressure system throughout the cardiovascular system, which keeps the blood flow pretty high and moving the blood quickly, which allows for the rapid transport and delivery of nutrients and gases. However, the high pressure and the high-speed transport does not optimize immune interactions. Now the lymphatic system, on the other hand, lacks an organ that serves as a pump, and so it relies on other means to propel lymph throughout the lymphatic system that we'll get to talk more about moving forward in our course. However, the lack of an organ that serves as a pump creates a relatively low pressure system that keeps the lymph flowing slowly. And this slow flow of lymph and low pressure optimizes immune activity, which allows the lymphatic system to perform immune surveillance and response.
Now, the cardiovascular system is going to have less variation in terms of the vessel locations across different individuals, which usually means that there are more vessels that need to be memorized when it comes to the cardiovascular system. However, the lymphatic system has more variation when it comes to vessel locations across different individuals. And because there's so much more variation, that means, usually, there's less to memorize when it comes to vessel locations. Now, the cardiovascular system has larger vessels that have a wall made up of 3 tunics or 3 layers that we talked about in previous lesson videos, and includes the tunica intima, the tunica media, and the tunica externa. And the lymphatic system also has larger vessels that can also have a wall made up of 3 tunics, which are going to be very similar to the tunics of the cardiovascular system.
Now the cardiovascular system has, some veins, especially the veins of the limbs, the arms and legs, that have valves, venous valves, that prevent blood backflow. And the reason that it doesn't need as many valves is because it's a relatively high pressure system. Now because the lymphatic system is a low pressure system, it is actually going to have significantly more valves than the cardiovascular system. So lymphatic vessels have even more valves than the cardiovascular system. Now the blood capillaries of the cardiovascular system are usually not permeable to relatively large substances, such as cellular debris and larger macromolecules, like larger proteins and fat molecules. Whereas the lymphatic system capillaries are going to be more permeable, to larger substances. And so the lymphatic capillaries are able to absorb those larger substances that most blood capillaries are not able to absorb. And so down below in this image, you'll notice that we've also included an image of the thymus and an image of the spleen, which are lymphoid organs that we'll get to talk more about moving forward in our course. But for now, this here concludes our video on the cardiovascular system and lymphatic system comparisons, and we'll be able to learn more as we move forward in our course and apply these concepts and problems as well. So I'll see you all in our next video.