 We have a pair of kidney that filters the waste that is produced in our body. It filters our body fluid and sends out all the waste and keeps us healthy. Now imagine a situation when this system breaks. Imagine a person that has non-functional kidneys. Well, all the waste and the toxins will build up to such an extent that it will kill the person. And in order to save a person who has non-functional kidneys, scientists have come up with two solutions. The first one is a kidney transplant in which the patient has to get a kidney from his family member or from a very close relative. And the second option is to let the kidney's job done artificially through an artificial kidney. But here the filtration is done outside the body. The body fluid is drawn out, filtered in this artificial kidney and then sent back into the body. Now, both these procedures has their own pros and cons, but kidney transplantation is a very, very expensive procedure. And also most of the time, a finding a donor who has a matching kidney is very difficult. That's the reason most people with non-functional kidneys opt for the artificial kidney or we also call it hemodialysis procedure. So in this video, we're going to learn what an artificial kidney or hemodialysis is. So if you look at the word hemodialysis, here hemo means blood and dialysis is taken from a Greek word which means to set apart or set free. And in this context, it means to set free the waste that is accumulated in the blood. And this is how the procedure when done looks like. Here is a patient who has a non-functional kidney whose blood is drawn out, filtered in a machine called dialyzer and then sent back into the body. Now for the ease of understanding and to get a hang of what all is happening inside this dialyzer, let's get rid of this complex looking machine first. And we will simplify the entire process and look at each step. Okay. First of all, we will elongate the tube that is withdrawing blood and sending it back again into the body. Okay. We will just consider it to be a long tube. Now this tube is made to pass through a fluid filled chamber and the composition of the fluid in it will be exactly the same as that of the blood plasma. Okay. Except that this fluid will have no ammonia or urea in it. We won't have these things in the fluid. Okay. Now a very important point to note here is that the part of the tube that is inside this chamber, fluid filled chamber is made of a special material called cellophane. Cellophane. And why is it so important? Because this material makes the tube permeable to small substances just like the cell membrane which is permeable to the fluid inside and outside of it. Right. Now how about you pause the video and think of what might happen when the blood passes through this chamber through a tube made of cellophane. Now as the tube is permeable, all the substances that is in excess in the blood will slowly diffuse out into the chamber. Right. They will move along their concentration gradient. Right. So all the substances that is in excess will move out like urea, ammonia and excess ions. Okay. Toxins. Everything that is in excess inside will move out. But the good good things of the blood like the blood proteins or the cells, they cannot move out of this cellophane tube because the pores are not sufficiently big enough. And we obviously don't want them to get out from the blood. Right. So the blood gets filtered here. All the waste is dumped in this chamber and the filtered blood is then sent back into the patient's body. And the fluid in this chamber is also constantly refilled. The fresh fluid is poured into this chamber and the fluid which is mixed with urea ions and all the toxins is also continuously removed from the chamber. Okay. Now the blood is continuously flowing through this tube. Okay. And as you can see in the picture, just a small part of the tube is inside this dialyzing chamber, which means that the blood stays for a very short time inside this dialyzing chamber and this diffusion process also has to take place very quickly. Right. That makes the process very inefficient. That's the reason scientists thought of coiling the cellophane tube inside the dialyzing chamber. This way, as you can see, the blood gets to stay for longer in the dialyzing chamber and the diffusion process can also take place very efficiently, thus filtering the blood even better. So that's the reason we get to see coils inside the dialyzer. So this is how the main filtration of the blood takes place. But when we deal with blood, we also need to take care of certain properties of blood. For example, every time a person bleeds due to a cut or a wound, after a few minutes the blood clots. That is because of the awesome property that blood has. And it is also because of certain enzyme that blood contains. Now in this case, we cannot let the blood to clot, right? The blood is oozing out of the body, getting into this tube, and it is very much possible for the blood to clot, right? But we do not want that. So in order to stop the blood from clotting, an anti-clotting chemical is pushed into the blood, which is called the hyperin, which is an anti-coagulant. When it is pushed into the blood, the blood remains in a liquid state. And again, after the filtration, when it is sent back into the body, the anti-hyperin drug is injected so that the blood regains its natural power of clotting. And this entire process is called hemodialysis.