 Hello, my dog, Pounds. I hope you guys are out there doing something really fun right now like settling down to watch your lectures, your physio lectures and study capillary exchange. For context, our entire lecture today is ultimately going to give us the reason why we have a cardiovascular system in the first place. Overall, in the course so far, we've looked at two main integrating systems. We've looked at the endocrine system and the nervous system. We've looked at a couple of primary effectors. We've looked at skeletal muscle function and cardiac muscle function. And now we're going to look at, dude, why bother having a heart other than the fact that it lets you love people? There's more reason to have a heart. Your heart pumps your blood and your blood goes through your capillaries and allows exchange. So we're going to ultimately get to the mechanics of that exchange in this lecture. Before we can do that, we kind of have to talk a little bit about blood flow in general and we have to talk about blood pressure. Now, we're going to have another entire lecture on blood pressure homeostasis because maintaining blood pressure and managing blood pressure is actually a pretty complicated phenomenon. But we have to understand it in general at this stage in order to appreciate capillary exchange. Now, where are we going next? Well, we're going to look next at the respiratory system and at a very important couple of molecules that are exchanged in the capillaries and that's oxygen and carbon dioxide. So let's start out with a review of blood vessel anatomy so that you are cool and you remember, I already know you're cool, so that you remember what capillaries even are in the first place.