 This section is called convoluted tubules. So who are we going to talk about? The proximal convoluted tubule and the distal convoluted tubule. Now, think for a second. If I'm looking at a slide of kidney, where am I going to see these guys? You're going to see them in the cortex. You're not going to see distal convoluted tubules or proximal convoluted tubules in the medulla of the kidney. How do you know if you're in the cortex? The glomerulus is easy to find. It's about the only thing that is striking the rest of the kidney slide. Literally looks like a bazillion tubes, circles with lumens. And sometimes lumens that don't really look like lumens, and is that a lumen? I don't know if that's a lumen, but if you think about a million nephrons in a kidney, of course it's going to be a bunch of tubes. Like the whole thing is nothing but tubes. That's what a kidney is. So we're looking for some sense of where it, what is all this? We're going to look for glomeruli. I'm going to show you a slide in a second that's going to show you what the glomerulus looks like. And we already know what the glomerulus looks like because we targeted in on that 20 lectures ago when we looked at simple squamous epithelium which is what the parietal layer of Bowman's capsule is made out of. We're going to expect to see distal convoluted tubule and proximal convoluted tubules in the same level of cortex that we see glomeruli. So let's go look at that. Once you're not seeing glomeruli anymore, you know you're in the medulla. And then who are we going to see if we're in the medulla? We're going to see loops of Henley and collecting ducts. So really it's pretty straightforward. The histology, right? Histology's always straightforward. Okay, so let's look at this picture of an actual slide. What do you see? First off, what is this knot of capillaries? This is my glomerulus. Now, you tell me. It doesn't look like the last picture that we just showed you. In fact, the last picture that I just showed you is right here. Can you see what is capillary in the potocyte or visceral layer of Bowman's capsule? Yeah, no. That looks like a mess of messiness. What I know is that there are potocytes there, and I know that there's blood vessels, capillaries there, and there's no way on the planet that I can tell the difference. Maybe somebody can. Holy tubes, what? Look at all these tubes. Just for perspective, are these tubes lined with simple squamous epithelium? Like what kind of epithelium lines these tubes? You're going to know, this is good review for your final, you're going to know what kind of tissue this is because you're going to look at the shape of the nuclei. Are they flattened and squamous looking? No, they're definitely not squamous looking. These are cuboidal cells. Some of them get a little taller, they kind of maybe lean toward columnar-ish, but for the most part, at least definitely what I'm seeing here, these are cuboidal cells. I see, are you ready for the distinction? I totally see distal convoluted tubule and proximal convoluted tubule. Are you ready to hear the difference? This one is distal convoluted tubule. This one is proximal. Proximal distal. Distal, that looks like proximal up there. What's the difference? Proximal convoluted tubule looks like a mess inside. Distal convoluted tubule looks clean inside. What? How could that be? Are you ready? Proximal convoluted tubule has microvilli on the luminal border. Why? Because 70% of all the filtrate that you filtered out, 70% of your 180 liters gets reabsorbed by the proximal convoluted tubule cells. How do they do it? Physio. Why do they do it? Physio. What are the structures that enable them to do it? Anatomy. They're covered with microvilli to increase surface area so they're more effective at reabsorption. Distal convoluted tubule, it still is reabsorbing stuff and it still is monitoring, not monitoring, modifying. Who's an M word? Modifying the filtrate but not doing nearly the action of the proximal convoluted tubule is. Okay. So can you tell the difference between them? Of course you can. And make sure when you're in lab and you find some, quiz each other. Really, quiz each other. All right, let's look at what the loops of Henley are like.