 Hey, everybody, Dr. O. In this video, I'm going to give a real brief introduction to the nephron. I'll do a much more detailed video later and then also do a separate video on what's actually happening at each step by ingredient, if you want to look at it that way. But this is a nice 10,000-foot view, so you have the real big picture of how the nephron here, the microscopic functional unit of the kidney, works. All right, so we're going to start here. Number one says the glomerulus. So what this actually is, the glomerulus is going to be this knot of capillaries. And there's a capsule, think of it like a cup, so you have the capillaries are going to be filtering out material. And this cup, the glomerular capsule or Bowman's capsule is going to catch it. When you put those two together, you have what's called the renal corpuscle. So the job of the renal corpuscle, this glomerulus, is filtration. And obviously, like all filters, it's going to filter based on size. First, let's talk about the amount, though. The average, your nephrons are going to filter about 180 liters, give or take, so around 50 gallons of fluid every day. So we've got some, so clearly moving forward, we're going to have to deal with we can't afford to lose 50 gallons of fluid a day. So we're going to reabsorb all that water or most of it, 99% of it at other locations. And then we're going to talk about, so the good news with filtration is that you can filter out small, bad things. So that's great. Things that metabolic waste products, organic waste products that have to be getting out of our blood can be filtered through the nephron. The good news is, number one, you can't filter out bad things that are large. So they're going to have to be actively secreted later on in the nephron. And number two, you're filtering out all the good things that are also small. So while you're filtering out metabolic waste products, you're also filtering out free fatty acids, glucose, amino acids, all of that, vitamins, minerals, things we can't afford to lose. So you will see that the glomerulus just think filtration, but we've got to immediately start to capture all this good stuff we're losing, the water and all those good things that I just mentioned. So that's the function of the glomerulus. First step here, then we go to the proximal convoluted tubule or the PCT primary job. And we're thinking we're talking primary jobs here because it's a brief introduction. Think reabsorption. It does secrete some things, but we're not going to focus on that here. Reabsorption. So we just filtered out 50 gallons of fluid. We have to reabsorb that. So 70% of the water is going to be reabsorbed right here at the proximal convoluted tubule. And then it's going to reabsorb almost 100% of those good things I just said, glucose, vitamins, minerals, fatty acids, all these things we cannot afford to lose. So without the proximal convoluted tubule, we would basically be peeing away all the things we need to sustain life. So glomerulus think filtration, proximal convoluted tubule think reabsorption. Then we have the loop of Henley. It's more complicated than this, but with the loop of Henley, primarily think the further reabsorption of water. So we reabsorbed 70% of those 50 gallons of fluid that they're going to the nephrons at the proximal convoluted tubule. You'll reabsorb another 15% of the total here. So the loop of Henley, its primary job is the further reabsorption of water. Remember, there are two types of nephrons. Cortical nephrons have short loop of Henleys. So they're not going to reabsorb that much water. But your juxtamedulary nephrons, even though they're only 15% of the total, they have really long loop of Henleys. So they're going to really concentrate your urine. All right, so loop of Henley, think further reabsorption of water and the concentration of your urine. Then we go to the distal convoluted tubule. It does absorb things, but in a word, I want you thinking secretion. The stuff we have to get rid of that hasn't been properly filtered out will be actively secreted here. So think secretion of waste products, drugs, toxins, these types of things, primary function of the distal convoluted tubule or the DCT. That's where a single nephron ends. Multiple nephrons will then fuse to become the collecting ducts. So the collecting duct, their job is to determine the final concentration of urine. So after all of these steps, we still have 27 liters of water to deal with. So the collecting ducts will determine how much of that 27 liters will reabsorb. And that's primarily under the control of ADH, antidiuretic hormone. Other things can play a big role as well. But as long as you have the appropriate amount of ADH and you're not overhydrated or dehydrated, it'll take that 27 liters of fluid and turn it into one to two liters of actual urine. Then these collecting ducts at the end, they fuse together and they drain into the renal papilla. And then they're going to fall the system we've already covered through a minor calyx, major calyx to the renal pelvis, to the ureter, to the bladder, and then to the urethra out of your body. All right, that's the quickest introduction I can do, a very complicated thing. We'll do a video about twice this long where we go into the details quite a bit. But this will be a nice one to come back if you're just doing a quick overview. Okay, I hope this helps. Have a wonderful day. Be blessed.