0:00 Arman Duhasudungan biology and medicine videos, please make sure to subscribe, 0:04 join 0:04 the forming group for the latest videos, please visit Facebook Arman Duhasudung 0:08 an. 0:09 In this video, we're going to look at the red blood cell life cycle or erythro 0:14 cyte 0:14 life cycle. So here, I'm drawing a blood vessel. A blood vessel contains red 0:22 blood 0:22 cells. Here are mature red blood cells and mature red blood cells are 0:27 responsible 0:28 for transporting oxygen around our body. But where do the red blood cells come 0:36 from? Well, they all arise from the bone marrow. So here, I'm drawing a bone. 0:41 The 0:42 red blood cells come from stem cells within the bone marrow. Erythropoasis is 0:48 the term used to describe erythrocyte synthesis or the production of red 0:55 blood cells. Hemopoietic stem cells can differentiate into pro erythroblast and 1:00 then early erythroblast. In the early erythroblast stage, we see ribosome 1:06 synthesis. And this is important because once the early erythroblast becomes a 1:12 late erythroblast, the ribosomes are synthesizing a lot of hemoglobin and so 1:18 we have hemoglobin accumulation. Hemoglobin is the molecule within red 1:24 blood cells that actually carry the oxygen. So this late erythroblast can then 1:29 develop into a normal blast. A normal blast already contains all this hem 1:34 oglobin. 1:36 A normal blast will then become a reticulocyte. A reticulocyte loses its 1:43 nucleus. However, it is not a red blood cell just yet. A reticulocyte 1:50 actually stays in the bone marrow for several days before entering circulation. 1:55 And once entered into circulation, the reticulocyte after about one to two 2:02 days or 24 to 48 hours, it will mature and become a erythrocyte. Eerythrocytes 2:09 are the red blood cells that we know that circulate and carry oxygen around 2:13 our body. But erythrocytes don't circulate in our body forever. It has a 2:19 lifespan of about 128 days, when it's aged or when it's damaged. And so when 2:26 it's aged or damaged, it has to be removed. Red blood cell removal occurs 2:33 in three main organs, the spleen, the liver and the bone marrow. So here I'm 2:39 drawing a few old red blood cells that need to be cleared out. And here I'm 2:44 drawing the spleen. Within a spleen, we have macrophages. And it is these 2:50 macrophages that will actually engulf these old erythrocytes and break them 2:55 down. And so when the old red blood cells are broken down, you end up with a 3:01 lot 3:01 of hemoglobin. The hemoglobin can then be broken down further into globin and 3:05 its heme component. Globin is then broken down to amino acids and the heme is 3:12 broken down to two main products, bilirubin essentially and iron. These 3:19 macrophages are not only found displayed as I mentioned, but they're also found 3:23 in the liver and bone. And they do exactly the same thing. Most of the 3:29 breakdown 3:30 product of red blood cells are recycled. So for example here the amino acids 3:36 will 3:36 enter back to circulation and then will travel to the bone marrow to be used in 3:41 erythropoasis again, the production of red blood cells. The iron and bilirubin 3:47 also have similar fates. So the iron, it can't actually travel in the blood 3:50 just 3:51 like that. It has to be attached to a transporter. And so iron obtains a iron 3:58 transporter from the liver known as transferin. And it's this way how iron 4:02 makes its way back to the bone marrow for erythropoasis. Bilirubin goes back to 4:10 the liver either through albumin transporter or whatnot. But essentially 4:16 bilirubin ends up in the liver. Now bilirubin has a few fates. Most of the time 4:22 bilirubin is actually secreted or excreted through the bile system. So bilirub 4:27 in 4:27 will enter the bile and then will be secreted into the duodenum of the 4:33 small intestine. And this is through the bile duct. So bilirubin is excreted in 4:40 feces or it is reabsorbed and is excreted in urine. Now that we're in 4:49 this picture of the stomach and small intestine, it's important to note that 4:52 when we eat nutrients, some of these nutrients are imported in red blood 4:57 cell production. They are absorbed this small intestine. So nutrients absorbed 5:02 for erythropoasis include amino acids, monosaccharides, lipids, vitamin B12, 5:08 folic acid and iron. And all these are used in erythropoasis because we need 5:14 these to make red blood cells. And as I mentioned the main function of red 5:21 blood 5:21 cell is to transport oxygen to tissues. So now let's look at one important 5:28 hormone or factor that influences erythropoasis. In times of hypoxia, which is 5:36 where when we have a decrease in oxygen levels, this will stimulate the kidneys 5:41 to produce an important hormone called erythropoatin. And erythropoatin is 5:47 such an important hormone in erythropoasis because it stimulates erythropoasis. 5:52 And so when you have kidney failure for example, your kidneys are not able to 5:57 produce erythropoatin so you usually develop anemia. I hope you enjoyed this 6:03 brief video on red blood cell life cycle. Thank you.
