I really feel like I haven’t spent practically sufficient time these days speaking to you about all of the silly and harmful issues that you are able to do to your personal physique, so let’s discuss doping. You most likely have heard of this due to Lance Armstrong, who secretly messed with his personal blood in order that he may illicitly win the Tour de France seven occasions in a row. You could be dimly aware of the truth that doping isn’t like capturing steroids, however it’s nonetheless dishonest, regardless that, like, why is it dishonest? And the way does it work? And is it even attainable to make your blood higher at being blood? In different phrases, how can some folks deal with — or mistreat — their very own blood prefer it’s some form of drug? Quick reply: As a result of your blood is extremely highly effective stuff. And its energy rests largely in your erythrocytes, or crimson blood cells. They’re essentially the most plentiful cell sort in your blood, accounting for practically 45 % of its quantity. Each time you are taking a breath, they choose up oxygen in your lungs and distribute it by way of your physique, after which seize carbon dioxide, and convey it again to the lungs the place it may be exhaled. The principle mission of erythrocytes is to maintain your physique fed with oxygen, so your muscle tissue can do their factor, and your mind can proceed to suppose and really feel and boss round your varied elements. However you don’t need to fiddle together with your crimson blood cells as a result of erythrocytes are bizarre characters. They go locations that different cells received’t. They purge themselves of their most valuable internal belongings, preferring as a substitute to stay as hole shells. Due to the crushing calls for of their job, they don’t stay very lengthy. And similar to together with your blood stress, an excessive amount of of those good issues can flip unhealthy shortly. So the erythrocyte have to be revered. It’s not for doping. Or for dopes. Regardless of their distinguished function in some worldwide sports activities scandals, your crimson blood cells are pretty easy and unassuming little cells. They’ve obtained a definite biconcave form — which simply implies that they’re concave on each sides — making them look kinda like a breath mint… a tiny, bloody breath mint. And whereas they’ve a plasma membrane, they don’t have a nucleus and don’t have most of the elements different cells do. In order that they’re mainly simply glorified, protein-filled phospholipid-bilayer sacks. However they’re nonetheless one other nice instance of that concord between kind and performance. For one factor, that biconcave form offers them a big floor space that’s supreme for gasoline alternate. It additionally makes them versatile, capable of change form as they squeeze by way of tiny capillaries with diameters smaller than the cell itself. After all, all that squeezing and twisting is tough on a cell’s membrane, and that, mixed with their normal lack of organelles to assist restore the membrane, means these cells don’t stay very lengthy, surviving on common solely 120 days. However they certain work arduous whereas they’re alive. And their work is generally in gathering and transporting oxygen. They’re capable of do this as a result of, if you happen to don’t depend their water content material, crimson blood cells are 97 % hemoglobin — a molecule that simply binds to, and releases, oxygen. It’s like an oxygen sponge. Each hemoglobin molecule is de facto fabricated from eight completely different element molecules — 4 are a crimson pigment referred to as heme, and 4 are a protein referred to as, you guessed it, globin. Every globin is a globular polypeptide chain — therefore its title — and proteins, you’ll most likely bear in mind, wish to bind to stuff. So every globin has its personal private ring-shaped heme molecule, and within the heart of that heme is an iron atom, kinda like a cherry on high of a protein-and-pigment sundae. It’s that iron within the heart of the heme that makes our blood crimson. By the way, not all animals have crimson blood, as a result of not all animals use hemoglobin to transfer oxygen. For instance, most mollusks like squids and snails have blue blood, as a result of it incorporates hemocyanin, a copper-rich protein-pigment that turns blue when uncovered to oxygen. However, iron is what we’re caught with, and I’ve to say it’s nice at its job, as a result of every iron can bind with one complete oxygen molecule. And that oxygen actually provides up. Since you might have 4 iron atoms in each molecule of hemoglobin and each crimson blood cell incorporates one thing like 250 million hemoglobin molecules meaning every considered one of your tiny, floppy red-breath-mints can seize a couple of BILLION molecules of oxygen. Precisely how they switch oxygen and carbon dioxide out of your tissue cells is one thing that we’ll get into once we discuss concerning the respiratory system. However if you happen to’re questioning why all this hemoglobin can’t merely skip the crimson blood cell rigamarole and simply run round bare in your blood, it’s as a result of free-range hemoglobin would truly thicken the blood, making it so viscous that it will impede blood circulate. This additionally occurs to play a component in blood doping, which — keep on with me — I’ll clarify in a bit. So what does the temporary however superb four-month lifetime of an erythrocyte appear to be? Nicely, bear in mind after I stated a crimson blood cell doesn’t have a nucleus? And possibly you thought, hey wait a second, how can it even be a cell and not using a nucleus, or DNA? To begin with, good catch. However truly, erythrocytes do begin off with a nucleus and DNA, they simply eliminate them, as a result of their complete goal for present is to schlep round hemoglobin and oxygen, they usually need the additional room. The entire means of forming blood cells, referred to as hematopoiesis, occurs in your crimson bone marrow, which is generally fabricated from reticular connective tissue that’s snuggled as much as particular capillaries referred to as blood sinusoids. Briefly, the method begins with a hemocytoblast — or a specialised stem cell — which quickly differentiates into an early erythroblast. Then, it begins making a complete bunch of ribosomes, the organelles that manufacture proteins. And on this case, the ribosomes begin cooking up tons of hemoglobin, because the cell transforms right into a late-stage erythroblast. When it’s obtained sufficient hemoglobin, it out of the blue jettisons most of its organelles, which causes the cell partitions to break down a bit, giving it its biconcave bloody breath-mint form. Now you’re left with a reticulocyte, which is just about simply an early erythrocyte that nonetheless has a bit group of ribosomes left, referred to as a reticulum. Thus far, this complete journey up to now has taken about fifteen days. When the reticulocyte is lastly bursting with hemoglobin, then it leaves the marrow and enters the bloodstream, and a few days later, when the final ribosomes have degraded, you’ve formally obtained your self a mature crimson blood cell. And that cell travels round your physique, doing its job for a couple of months earlier than it will get previous or broken and must be changed. Now, sustaining the stability between manufacturing and destruction of those cells is essential. Too many will make the blood too viscous and troublesome to pump, and too few results in oxygen deprivation, or hypoxia. The method of sustaining the precise ranges of crimson blood cells is regulated by a particular hormone referred to as erythropoietin, or EPO. It’s produced principally within the kidneys, but in addition in the liver, and is consistently circulating within the blood. Should you’re anemic, or mountaineering at a excessive altitude, or hemorrhaging blood, or experiencing something else that creates a drop in your blood oxygen ranges, sure cells in your kidney will discover, and take motion. They usually can try this, as a result of they traffick in a signaling molecule referred to as hypoxia-inducible issue, which screens your blood’s ranges of oxygen. The best way that this works is fairly cool. These particular kidney cells want oxygen so as to interrupt down that signaling molecule, so if oxygen ranges within the blood are low, they can’t flip the sign off. Which means that the sign retains going, which triggers the launch of an increasing number of EPO, which stimulates your crimson bone marrow to pump out extra crimson blood cells to hold round extra oxygen. As oxygen ranges in your blood improve, the sign is degraded, and EPO manufacturing slows. And EPO is a key participant in blood doping too, however we’re gonna have to attend a minute earlier than we get there, as a result of I first need to get again to the destiny of your hard-working erythrocytes. So if you happen to’re producing about two million new blood cells each second, you even have to eliminate about the identical variety of useless ones to take care of the stability, proper? When these cells get previous, they flip inflexible, and their hemoglobins begins to disintegrate. As they get stiffer, they will find yourself getting caught in capillaries in your mind or coronary heart, which might not be good. Fortunately, you might have sure channels to corral these dying cells, particularly across the spleen, which some anatomists name “the crimson blood cell graveyard.” So these drained previous cells get trapped after which mainly ambushed by massive macrophage white blood cells within the spleen, liver, and bone marrow, which break them down and recycle their varied parts. The globin proteins are damaged down into their primary parts — amino acids — which go again into the blood for use by different cells for making extra proteins. Iron from the heme group is separated and both sure to proteins and saved within the liver, or put proper again into a brand new hemoglobin molecule. And the heme will get became bilirubin, a yellowish pigment that goes to the liver the place it’s added to the bile that it secretes into the gut and ultimately leaves the physique in your poop. Now that you understand how your erythrocytes perform naturally, it’s simpler to see how they will be messed with — typically with unhealthy outcomes. You possibly can dope your blood in a couple of alternative ways, however the commonest method is to inject man-made or natural EPO hormone to spice up your crimson blood cell manufacturing. It’s additionally attainable to attract and retailer a few of your personal blood, after which transfuse it again into your physique after your physique has recovered from the blood loss, successfully elevating your quantity of crimson blood cells. The logic, if you happen to can name it that, is that extra crimson blood cells equals extra oxygen being carried to your muscle tissue, and due to this fact higher bodily efficiency. Now, the additional oxygen can’t change your precise muscle energy, however the added cardio capability does scale back muscle fatigue and improve endurance, by permitting your muscle tissue to work tougher for longer. And it could actually present sufficient of an additional edge to win a race, like, say, the Tour de France. Seven occasions. However not solely is it banned in athletic competitions, blood doping can be harmful. As a result of, bear in mind, a crimson blood cell depend that’s too excessive thickens the blood, and that really makes it tougher for the center to pump blood across the physique. As well as to defeating the aim of enhancing the blood’s effectiveness, this could result in blood clots, and strokes, and coronary heart failure. So, no thanks. Plus, dishonest sucks. However at present you discovered concerning the construction and performance of your erythrocytes, and of hemoglobin, which they use to hold oxygen. We additionally went by way of the formation and life cycle of a crimson blood cell, and studied how their ranges are regulated by EPO and their signalling molecules. Lastly, we discovered how doping the blood is a recipe for catastrophe and for locating your self on Oprah and apologizing to everybody you understand and shedding your whole yellow jerseys. Because of all of our Patreon patrons who assist make Crash Course attainable for themselves and for everybody without cost with their month-to-month contributions. Should you like Crash Course and need to assist us hold making movies like this one, you possibly can go to patreon.com/crashcourse. This episode was filmed within the Physician Cheryl C. Kinney Crash Course Studio, it was written by Kathleen Yale, the script was edited by Blake de Pastino, and our guide is Dr. Brandon Jackson. It was directed and edited by Nicole Sweeney; our sound designer is Michael Aranda, and the graphics workforce is Thought Cafe.