- The kidneys are very important organs when it comes to filtering the blood among other things. But in order to really understand how they function, we have to look at the blood supply to the kidneys, and that's what we're gonna be doing in this video. Let's do it. (upbeat music) Hey, what's up, Leslie Samuel here from Interactive Biology TV where we're making biology fun. And what we're gonna do in this video is we're gonna look at how blood gets to the kidneys through the kidneys, and then back out of the kidneys to go back to the heart. Now we all have hearts, fortunately, and the hearts are responsible for pumping blood throughout the entire body. The major vessel that leaves the heart to get to the bulk of the rest of the body is the aorta. Now, the aorta goes down through the thoracic region, down into the abdominal region, and as it's traveling throughout the body, it is sending off different branches. Now, here, we're looking at the abdominal aorta and some of the branches that are coming off of it. As you can see, we have blood that's coming down through the abdominal aorta, and then we have these two branches, one going to the left kidney and one going to the right kidney. These are your renal arteries. Whenever you hear the word renal, you know it's referring to the urinary system. And in this case, it's the branches that are coming off of the abdominal aorta and going to those kidneys. Now let's take a closer look at what's happening here. Now, once again, we have the renal arteries, one on the left and one on the right, and that is sending the blood to the kidneys. About 20% of the blood that's leaving the heart actually goes via the renal arteries to get to the kidneys. Then the renal artery is gonna split to go to the different sections or the different segments of the kidney, and those arteries are called segmental arteries. You have these branches and they are going to the different regions. These are then gonna split into other branches called interlobar arteries. And I remember this by saying, they're going in between the different lobes of the kidneys and really what I mean by this is the pyramids that you see in the kidney, those are what I'm referring to as lobes. Now, as those interlobar arteries are going in between those pyramids, you're gonna see it reaches a point where it kinda arches and that where it arches, that is when it becomes the arcuate arteries. Arcuate, referring to that arch, it's going around the pyramids. And then it's gonna send of these branches called interlobular arteries. Now I know this is a lot of terms to learn, but I want you to understand the sequence in how the blood is gonna get to the different parts of the kidneys and more so to the functional unit of the kidneys, which are the nephrons, and this is where it happens. Off of those interlobular arteries, we're gonna send off these little tiny branches and those are called the afferent arterioles. This is really how the blood is getting into these nephrons, and the nephrons are the functional units of the kidneys. We're gonna get into more detail about the nephrons in the next video. For now, you just need to know, this is where the bulk of the processing is happening. From the afferent arterioles, we're gonna get to a very important structure called the glomerulus. This is where the filtration is happening. This is where we're gonna go into much more detail in the later videos. And from there, we're gonna go via the efferent or efferent arterioles, taking the blood from the glomerulus down into an extensive network of capillaries that we call the peritubular capillaries. Whew, that's a mouthful, and there's a lot of important stuff that's happening right here. But for now, what I want you to know is that in the nephron, we have the afferent arterioles going into the glomerulus, going into the efferent arterioles, and down into this extensive capillary bed called the peritubular capillaries. Now we've gotten the blood to the kidneys, we've gotten them to the nephrons, the functional unit, and now we need to take the blood away from the nephron, away from the kidneys. And we're going to do this via the veins. And what you're gonna notice is that, just like we have all these named arteries coming into the kidney, we're gonna have these similar named veins going away from the kidneys, and we're gonna review that in a sec. For now, let's revisit what we have so far. So we have the abdominal aorta, that's the main vessel coming off of the heart. That's then gonna send off, our renal artery is going through the kidneys, our segmental artery is going through the different sections of the kidneys. We're gonna have then our interlobar arteries going in between the pyramids. It's gonna then arch around and give us our arcuate arteries. Then it's going to send off those interlobular arteries, which are gonna send off the afferent arterioles. And from the afferent arterioles, we're gonna go into the glomerulus where the filtration is really happening. We're gonna leave the glomerulus via the efferent or efferent arterioles, which then sends off those extensive peritubular capillaries. And from there, we have to go via the veins back, so this is how it's gonna work. The peritubular capillaries under venous end, is gonna lead to the interlobular veins, which is then gonna go via the arcuate veins to the interlobar veins. And then depending on which textbook you're reading, you're gonna see something different here. You're going to see, in many cases, it skips the segmental veins and go into the renal veins so that it can go back via the inferior vena cava to the heart. Now I said, depending on which textbook you read, because in some textbook, it will actually include the segmental veins. I want you to know that that is an option, but in most cases, you're just gonna see it going from the interlobar to the renal veins, and then back to the inferior vena cava, which then goes back to the heart. That is the entire process of sending blood all the way to the kidneys, through the kidneys, and out of the kidneys. In the next video, we're gonna dive deeper into the nephron, the structure and its function, so I'll see you over there.