 Hey everybody, Dr. O here and this video we're going to talk about the external and internal anatomy of the kidneys. So here you see the kidneys, see the ureters as well. So the kidneys and ureters are retroperitoneal, meaning they're behind the parietal peritoneum, the peritoneal cavity that covers most of your abdominal and pelvic organs. Location wise, see the left kidney there sits at the areas from T12 to L3. The right kidney is going to be a little bit lower because it's being displaced or pushed down by the liver so that's going to be its location in your body. You're right up against the posterior abdominal wall. The outside of the kidney, there's a tough fibrous capsule around the kidney. This is really good news, like for example if someone gets kidney cancer and it's localized to that kidney, that capsule will help contain it to the point where just removing that one kidney should be good as long as the cancerous cells haven't left that area. So there's a fibrous capsule around the kidney. Outside of that you're going to see a fat pad, you don't see it here but there is a fat pad around the kidney. So even if you're very lean, you should still have a fat pad. If someone has anorexia or they're starving for some other reason, you can actually digest this fat pad and can lead to something called ptosis where the kidneys will drop. So this fat pad is supposed to be there partially because the kidneys aren't fully protected by your ribs as you can see in this image. So the fat pad is supposed to be there to protect your vulnerable kidneys and if it's not, then it can actually cause them to move out of their proper location as well. Again that's called ptosis. Another thing you don't see here but sitting on top of the kidneys, they're not really related except for location wise, sitting on top of the kidneys you would have the suprarenal or adrenal glands which they're going to produce your adrenal hormones. We covered that earlier. All right let's go ahead and look inside a kidney. So if you were to bisect or dissect a kidney, split it right down the middle, this is what you would see. The outside of the kidney is called the renal cortex and the inside is the renal medulla. You hear that a lot, the cortex on the outside like the bark on a tree and then the medulla. And you're going to see between 6 and 18 of these renal pyramids. So they're pyramid shaped but at the apex or tip of these pyramids you're going to have what are called renal papilla which papilla means a nipple like structure. These renal papilla are going to be bunches of collecting ducts. So we'll cover the nephrons in another video but the nephrons are where urine is made. The collecting ducts collect them and they're going to drain this newly formed urine out of the renal pyramids through this renal papilla to what are called the minor calyx or the minor calyces. Now it's a funnel. The minor calyx, two or three of those will drain into a major calyx and then all the major calyces or all the different major calyces will fuse into what you see there called the renal pelvis. The renal pelvis is this funnel that's taking all the urine that was produced in these microscopic nephrons and it's funneling it down and the renal pelvis is where urine leaves the kidney. So now urine is in the ureter and it's traveling down towards the bladder. You see the renal columns between the renal pyramids. If you look at a renal pyramid plus the renal columns around it, that'd be what's called a lobe of the kidney. So just if you ever hear that term, the lobe. Other important things here, the renal hillum. So the hillum is going to be the area where everything enters and exits the kidney. So it's going to be arteries, veins, nerves, etc. That's called the hillum. I think those are all of the key terms there though. So that's the basics of the internal structure of a kidney. Just to review real quickly, the microscopic nephrons where urine is produced, they're going to be captured by the collecting ducts. Collecting ducts are going to be funneled down these renal pyramids to the end called a renal papilla. They're going to be, the urine's then going to be dripped into a minor calyx, which will drain into a major calyx, which will drain into the renal pyramid, or sorry, renal pelvis, and that's going to drain into the ureter. So that's going to be how the filtering or funneling, sorry, function of the kidneys works. Just to introduce them here, we've covered the internal anatomy on the far left of the kidneys, but the microscopic anatomy is going to be the nephron. So I'm going to tell you now is you have about 1.25 million nephrons per kidneys, and the nephron is the functional unit of the kidneys. This is going to be where filtration, secretion, reabsorption, concentration of urine actually takes place, but that'll happen in another video. Okay, I hope this helps. Have a wonderful day. Be blessed.