 Hi, guys. We're back for part two of kidney function. And in order to get started on our next task in dealing with the kidney, it's probably a good idea to review the nephron overall. So let's just go ahead, suck it up, life is good. Let's draw ourselves a nephron. In the last lecture, we dealt with the process, which is mostly the process of filtration, which is very important and takes place from the glomerulus, a knot of capillaries, and into Bowman's capsule. This is Bowman's capsule, which flows into the proximal convoluted tubule, which descends down into the descending loop of Henle, which then turns into the ascending loop of Henle, which travels up by the Bowman's capsule all over again, and into the distal convoluted tubule we got there, where it dumps into the collecting duct. How's that? Perfect, right? We remember that the glomerulus is the knot of capillaries that is exposed to, I don't know what it's exposed to, it's where the blood is filtered out of the capillary and into Bowman's capsule. Okay, you followed all that. This is my nephron. Now, in the last lecture, we dealt with this process right here, which was filtration, and that was our whole topic. For an hour, all we did was filter stuff out of the blood. In fact, we filtered out 180 liters of stuff into the blood every 24 hours. That's shocking. Obviously, we better not pee out 180 liters of fluid every day. Like, we have to go through the process of reabsorption. Reabsorption is taking what was in the filtrate and bringing it back into the blood supply. You can imagine that there is a tremendous amount of reabsorption that's going to happen. Now, the strategy of the kidney is kind of the mom rigs strategy of room cleaning for small boys. Everything gets filtered out. When I go through my children's room, first of all, I try not to, but if things become desperate it is time for me to tackle the room. My strategy involves getting a box or a giant garbage can and dumping everything into it. This is what the nephron accepts, everything. It doesn't matter what's in the blood. The only thing that doesn't come through into the garbage can of the nephron is plasma proteins. They're too big, and blood cells, they're too big. Everything else, sugar is filtered out. Any kind of vitamins, enzymes, all that stuff, just ions, all of it gets filtered out. Calcium, sodium, potassium, chloride, all of it is dumped into the nephron. So we're going to look at each place in our nephron and talk about what is reabsorbed. What are the strategies that are used to reabsorb stuff back into the blood supply? So the proximal convoluted tubule is where we're going to start and 70% of everything that's filtered out is reabsorbed by the proximal convoluted tubule. This is important, and we're going to look at some of the mechanisms for how this is done.