 We've got to have a blood supply. The whole point of this is to filter the blood. So somehow we're going to have to get intimate connection between our nephron and blood. And ultimately, we're going to move fluid from the blood into the nephron tubule, into this tube right here. That's the whole point. So let's throw in some blood structures. What's going to be the overall? Who brings blood to the kidney overall? It's going to be the renal artery. And who drains blood from the kidney overall? The renal vein. No problem. And there are many additional branches of renal blood vessels that we're not going to deal with. The one that we care about and that we want to spend some time looking at is called the afferent arterial. And does it work for you that ultimately the renal artery is going to branch into a whole bunch of afferent arterials? There is going to be one afferent arterial for every single glomerulus in your kidney. So there's a million of these afferent arterials in each kidney. I'm going to draw you the afferent arterial. Afferent, what does it make you think? Going toward something. And in fact, we're going toward the structure that I'm going to draw next, which is called the glomerulus. So the afferent arterial is this thing right here. And the afferent arterial feeds into a knot of capillaries called the glomerulus. See what I just did here? This, I'm going to label it in black. That right there is my glomerulus. I feel like I want to show you a picture of a glomerulus. It looks like we have some time to look at the anatomy of that thing in particular. But right now, think of it as a serious, hardcore tangle of capillaries. It's not a net of capillaries, it's a tangle. One vessel, the afferent arterial, feeds into this net of capillaries. Notice the proximity of this capillary net to Bowman's capsule or the renal corpuscle, this area here, the glomerular capsule. Afferent arterial feeds in, guess who feeds out? The afferent arterial. And here's something that is really interesting. Notice, if you will, the different diameter of the afferent arterial as opposed to the afferent arterial. Blood comes into the glomerulus through the afferent arterial. It's hanging out in the glomerulus, but now it has this much smaller exit route through the afferent arterial. It's significant, and that's very significant to understanding nephron's function. Afferent arterial, you ready for this? Afferent arterial feeds into, now this is a net. It is not a line, I'm drawing it like it's a line. And I'm drawing it like a line so that you can kind of visualize the ultimate outcome. And I feel like it's probably a good idea for me to make this a tube so that you can see. This tube is another net of capillaries. Okay, so the afferent arterial feeds into another net of capillaries that I've just drawn as one structure here, but this is actually a net. And this is, they're called peritubular peri-around tubular around the nephron tubule, peritubular capillaries. And they surround the nephron in a net, and they actually play a role in reabsorbing stuff that we filter out into our nephron. Peritubular capillaries, in some nephrons, there is a very long peritubular capillary called the vasorecta. And this is also significant for understanding function. So keep this in mind that one example of a peritubular capillary, a specific example of a peritubular capillary is the vasorecta. We're going to talk about the vasorecta again. The other thing that I just want to throw out there, is I want you to just notice this right now. Look at the way that I drew the blood flow. Do you see how my blood, and then ultimately, ugh, that makes it look like my blood is heading out through the collecting duct. It's not, it's headed out through the renal vein. Do you see my whole blood flow here? Really fast, just for the fun of it, because you know it is so much fun. Just draw in arrows, orange arrows, showing filtrate, showing pre-P. Remember we started in Bowman's capsule, we went into the proximal convoluted tubule, down the descending loop of Henley. What do you notice right here? Up the ascending loop of Henley. Notice that the blood supply and the filtrate, they're moving in opposite directions. That is extremely significant for function. You now have a blood supply and a tubule. Now I want to look at what are the, we can actually boil down all nephron function to four things. And understanding those four things is going to be critical for looking at the specifics of each part of the nephron that we're going to look at. Okay, so mechanisms of function, that's what's coming next.