 Hey everybody, Dr. O here. So we've talked about how red blood cells are made and how they're used. Let's talk about what happens when we're done with them. So the average red blood cell is going to survive for about 120 days in circulation. Once it's worn out and ready to be replaced, it will be removed by macrophages. So your big eaters, your phagocytic immune cells, most of these macrophages are going to be in your bone marrow, your liver and the spleen. So some red blood cells just kind of die and are destroyed in circulation, but most of them are going to be taken up by those three locations. Bone marrow, liver and spleen. The iron's going to be stored and reused, which is why these areas have lots of iron. The protein component of your red blood cells is going to be broken down. So it's going to be degraded into something called biliverdin, which is a green pigment. And that is then going to be turned into bilirubin, which is a yellow pigment. So the cool thing is this bilirubin is actually used when we make bile, when we make new bile. So broken down red blood cells play a huge role in the production of bile, which we'll cover in the digestive system. But some of this is going to be further broken down in your large intestines. This bilirubin is broken down by bacteria into something called stercobilins, and that's what gives feces its brown color. The kidneys can also remove this bilirubin, and it's going to be secreted as what are called urobilins, which is going to make your urine yellow. So the yellow color of your urine and the brown color of your feces are both the results of the breakdown of red blood cells. Now, of course, this is happening two to three million times every second. So there's going to be a lot of these products around. Lastly, so if your liver is failing and you can't get rid of this bilirubin and put it into bile and use it properly, that's why it's going to build up in the body. And that would be jaundice. So if someone is starting to get a yellowish tinge, then the big concern is that their liver is failing, and that's what jaundice would be. So the breakdown of these red blood cell products is still happening, but you can't actually properly get rid of the bilirubin and it builds up in tissues. That's kind of cool, not for that person, of course. All right, so that is the basics of how red blood cells are going to be broken down and its parts are going to be recycled. And this process is going to happen, again, two to three million times every second in your body. I hope this helps. Have a wonderful day. Be blessed.