Source: Video and Images Created by Amanda Soderlind
Welcome to this lesson today on the urinary system.
Today we will be taking a look at the structure and function of the urinary system. So overall the main goal of the urinary system is to help eliminate waste from the body, and to maintain the composition and level of water and solutes of the blood and other extracellular fluids. Those are the two main things that the urinary system does, is eliminate waste and maintains water and solute levels for blood in extracellular of fluids.
The main parts of the urinary system include the kidneys, ureters, urinary bladder, and the urethra.
We're going to go ahead and label that our diagram right here. This is the urinary system as a whole. We have our kidneys. And we have two of them, and then each kidney is connected to a ureter. The kidneys are the filtering organs of our body which form urine, and then they're connected to these ureters, which are these tube-like structures that basically just connect the kidneys to the urinary bladder. As urine is produced in the kidneys, it flows down the ureters, and into to this structure here, which is the urinary bladder. The urinary bladder, basically its function is to store urine. So urine is produced, and then it's stored in this urinary bladder until it can be excreted. And then the urinary bladder is connected to the urethra. The urethra is a tube that connects the urinary bladder to the outside, and allows you to expel urine.
If we take a look at this next diagram here, we're going to look a little bit more closely at the structure of a kidney. So this diagram right here is just a diagram of a kidney. It's a cross section of a kidney.
Let's take a look at some of the major structures associated with the kidney. We're going to start here by identifying the renal artery. We know that the kidneys are filtering organs of the body. So blood will enter the kidneys in order to become filtered. Blood enters through these renal arteries. The renal arteries deliver blood to the kidneys. And then the renal vein, here, returns blood back to the body that has already been filtered. So blood enters enter the renal artery, becomes filtered, and then leaves through the regional vein.
Now, as it enters through this artery and becomes filtered, the process of urine information occurs. So depending on the solute concentration in the blood, or the amount of water that's being carried, those factors will determine how much urine is produced.
Some of the different parts of the kidney associated with urine information are the renal cortex, and the renal medulla.
A structure called nephrons are found in the kidneys, and they are the actual structures involved in filtering water and solutes from the blood. We're going to get into their structure in just a moment here. But basically, nephrons are found in the renal cortex, and they also span the renal medulla. So these two parts of the kidney are where the nephrons are found. And then those are the structures that actually filter the water and solutes from the blood, and are involved in urine formation.
The renal pelvis is this part-- this kind of peachy-colored part right in here. And the renal pelvis, its function is basically just to funnel urine towards the ureter. So once the water and the solutes have been filtered as they move through the nephron, urine can be formed, and then urine is filtered through this renal pelvis and towards the ureter. So this is the ureter. And remember from our last diagram, the ureter basically carries the urine formed by the kidneys down to the urinary bladder for storage.
The next structure I want to identify here is the renal capsule. And this basically is just a fibrous covering on the outside of the kidney. So these are the different structures here, of the kidney associated with urine formation.
As I mentioned, nephrons are the specific structures in the kidney that span the renal cortex and renal medulla, that actually filter the water and solutes from the blood. So let's take a brief look here at the structure of a nephron.
This here is a nephron. So the first part here, this bulb that we're looking at right here, is the Bowman's capsule. Within the Bowman's capsule, we have the glomerulus, which is a cluster of blood capillaries that perform the first step of filtering blood.
We also have afferent arterioles. So we're going to call this our afferent arteriole. And basically the afferent arterioles deliver blood to the nephron. So blood is delivered to the nephron by the afferent arterioles, and enters the bowman's capsule, where the glomerulus is. And then from there, it basically looks like, kind of like the piping underneath your sink almost, if you think about it. So as it passes through the different structures of the nephron, different processes happen in order to form urine and to reabsorb water back into the body.
The next part here is the proximal tubule. And then down here, we have the loop of Henley. And then the distal tubule. And then from there, it moves into the collecting duct. And the collecting duct then will collect urine and then carry it on elsewhere, towards the real pelvis and the ureter, so that it can collect in the urinary bladder. And then, not labeled on this diagram here, just for simplification reasons, but capillaries actually also weave themselves around the nephrons, and these will deliver filtered blood back to circulation.
So these arterials and these capillaries are also involved in this process, as well, but they're just not labeled on this diagram to make it a little bit more simple. But if you are curious in figuring out exactly what each of these parts of the nephron is for, and what occurs in each parts of those nephrons, you can look up different tutorials on the process of urine formation, such as filtration, reabsorption, and secretion. And then find out exactly where in the nephron each of these processes is occurring, and what's happening during each of those processes.
This lesson has been an overview on the urinary system, structure and function.