hi everybody Dr Mike here in this video we're taking a look at a process called hematopoesis which is the production of blood cells in the body not just red blood cells this is termed arthop poesis which we will cover but hematopoesis are all the blood cells now in actual fact we should probably say formed elements instead of blood cells because platelets aren't cells they're cell fragments but we'll get to that point so let's take a look at hematopoesis [Music] first thing you need to understand with hematosis is it all begins with a stem cell and this stem cell that we'll draw up here we're going to term an heat hemato poetic stem cell all right so if we have a look at this homat poetic stem cell what's important about this firstly it's what we call Pur potent has the capacity to turn into a whole bunch of different cell lineages or cell cell types but the other great thing is that it also makes sure that even though it goes down these various lineages it still makes copies of itself so it maintains a stem cell population that's very important now the thing is that generally speaking as an adult these hematopoetic stem cells are located to our in our red bone marrow red bone marrow but the thing is it's not always in our red bone marrow so if you think about it in utero or if we think about uh gestationally at 2 weeks 2 weeks just stational it's in our yolk Sac this is where we have our hematopoetic stem cells then what we find is that around about 3 months just stally it's going to be in our liver and spleen that's where we make these blood cells and and then by the time we are born so at Birth it's going to be relegated to our red bone marrow and we term this mallary hematopoesis because it's located if we have a look at our bones we know that if I take a long bone for example and I draw a bone just like you'd see a bone on a cartoon here's a long bone inside the shaft of the long bone is called the medala and in this medala we can have red bone marrow now at Birth most of our bones will have red bone marrow in the Maller cavity and again called mallery hematopoesis but as we become an adult at around about 20 years old probably close to 50% of the red bone marrow will turn into yellow bone marrow now yellow bone marrow is basically just fat it doesn't undergo the process of homat poesis unless it's triggered due to some particular event like it's really needed for whatever particular reason all right now the thing is that at adulthood the red bone marrow like I said there's only like 50% of the bones the bone marrow has red bone marrow in it now what bones this is generally relegated to the axial skeleton by adulthood so that's things like so most of the red bone marrow by adulthood is axial skeleton axial skeleton so that's things like flat bones so think of the scull think of the sternum but then there's also things like the vertebral column the pelvis and then you're going to find it in the ends of the long bones such as the femur and the humorous so by the time you're in adult Hood that's where the red bone marrow is located and that means that is where the process of hematopoesis occurs now let's take a look at this particular process hematopoesis we're starting off with like I said that stem cell the hematopoetic stem cell and it generally goes down two lineages two lines so the first that I want to go through is that where it creates what we call lymphoid precursor cells or let's call them lymphoid progenitor cells there's a whole bunch of different names sometimes they're called common lymphoid progenitor cells common lymphoid precursor cells they're all the same thing the other lineage that can go down is the myoid precursor cells or myoid progenitor cells let's be consistent all right there are the two Pathways it can let's draw the cell up just so we know what's going on okay I want to start with the lymphoid progenitor cells what this ultimately will produce are our tmb cells so what I want to do actually is let's draw a blood vessel here let's draw a blood vessel that's going all the way along here because some of these red blood cells are going to be in the blood vessel some of they going to go into the tissue and then out here we got the tissue so I'm going to write blood vessel here blood vessel and then down here I'm going to write tissue and I'm going to right tissue here Perfect all right so let's look at the lymphoid progenitor cells what they will turn into a couple things firstly they can turn into and let's do this in Black so they can turn into what we call NK cells now NK stands stands for natural killer cells and these natural killer cells are part of the innate immune system and what they do is they're really good at targeting infected cells and simply just killing them off so we've got these enk cells right simple the other thing it can do is it can turn into what we call lympho blasts now blasts as a suffix tells you it has the capacity to turn into something right it's immature and so lympha blasts can turn into te- cells and it can turn into B cells so these are what we call our lymphocytes right and so remember this thing though right the the B and the t is telling you where they mature so the B cells mature in the bone marrow now where are we right now with all this process happening this is the bone marrow so I've got blood vessel here tissue here let's write bone marrow because that's where we are we're in the specifically the red bone marrow so these B cells they stay in the bone marrow to mature and then once they're matured they can be tossed into the bloodstream all right I'll get back to that in a sec but tea cells the T stands for thymus this is where they mature and so what happens is these te- cells will go into the bloodstream but they'll move out of the bloodstream and they will go into other tissues such as the thymus and lymphoid tissue so we've got lymphoid tissue here right and this is where the tea cells will mature now what do they mature into they can turn into t- helper cells and they can turn into cytotoxic te- cells now what happens here at the thymus for example if is it gives them glycoproteins it modifies them and it modifies them by giving them these little signals on the surface and for example t- helper cells get this uh CD4 positive glycoprotein on the outside and the cytotoxic tea cell gets this cd8 positive on the outside and now they're more mature and so what they can now do is they can now jump back into the bloodstream and they'll inter interact with B cells and as we know B cells can also seed these lymphoid tissues as well and what B cells can do is B cells can turn into plasma cells and plasma cells produce antibodies perfect and we know that from my immune lecture that tea helper cells cytotoxic tea cells they work with the plasma cells or the antibodies and they all work together to signal each other call in uh either each other or they will call in other cells of the complement system for example um to help with fighting infection so as you can see this is the lymphoid progenitor side let's take a look at the myoid progenitor side this turns into a number of different things first thing I want to focus on is the myoid progenitors turning into or going down the lineage of red blood cells so first is something called a pro erro blast Prothro blast so we know they're called arthro sites red blood cells but the blast means immature Pro means it's an early version of an immature arthr blast so a Prothro blast will actually turn into an arthro blast and there's actually a number of different stages after this but I'm going to cut a couple out and show you the most important ones arthr blast will turn into a reticulite reticul site now reticul site is not a mature red blood cell it jumps into the bloodstream out of the bone marrow into the bloodstream now a reticular side in the bloodstream okay firstly what's it look like right it looks like a red blood cell basically but the reticular refers to reticulation network it's got ribosomal um components inside of it so it hasn't fully gotten rid of all of its intracellular organel yet once it does and it's fully emptied itself of a nucleus and organel and so forth it now has the capacity to pack itself with hemoglobin and this takes around about 1 to 2 Days in the bloodstream once it does it is now a mature arthrite it's now mature arthrite which we call a red blood cell and we have around about 5 million arthr sites per microliter why is it important to highlight these two particular points well it's important because we if we take blood we can measure both reticular sites and arthos sites and that can give us an indication of possibly the origin of certain types of anemias for example if the arthrite levels are low but the reticulite levels are high it's telling us that this process is fine but the red blood cells are getting killed off when they mature likely something called hemolytic anemia or if both are low maybe it's a problem with the production and when what we know is when it comes to the production of red blood cells there's a couple of really important things we need early on for the process to occur these things that we need include folate B12 and iron now all of these we get from our diet so if we're deficient in these we will not have hemolytic anemia right we can have anemia but it's happening from an earlier stage so that's important point so we've got the uh arthr poesis so let's write this down so this is arthro poesis this process I'll do an asteris arthro pois I'm going to go back and talk more about it shortly this here is called lympho pois lympo pois all right what else do we create here from this myoid progenitor cell or common myoid precursor cell so we also have myoblasts so here we can have actually I'll move it more across we've got heaps of room we can have Milo blasts now Milo refers to bone marrow which is where we are and this is interesting because you could argue that arthro blast are Milo and the other ones I'm going to talk about shortly are Milo but we've got myoblast here and they make a number of different important cells firstly the myoblast can turn into granular sites granular sites so these are cells that have granules inside of them there's actually three that it makes right the three granular sites that it makes are going to be neutrophils basophils and eosinophils eosinophils eosino fills all right now the granular sites now what a granular site means is that if you stain it and look inside they got granules inside those granules are important in fighting off infection so neutrophils basophils eosinophils now I didn't draw up an arthrite I'm going to go back to it but there's a red blood cell I'll get back to that in a sec that's the granular side neutrophils are the first cell type that's called in upon infection and they form P after a while because what they do is they start to clean everything up and they basically die and their remnants remain and that's the pus basophils and eosinophils are important in allergic response and parasitic infection right so these are the granular sites that have come from myo blasts but myo blasts can also produce another blast cell which is called a monoblast a monoblast what a monoblast can produce is a monoy and a monoy is now floating through the bloodstream here's the thing though monit so you've got an infection neutrophils are called in first second are monocytes now monocytes are the name that they're given when they're floating through the bloodstream but once a monite leaves the bloodstream it turns into a maccrage now maccrage is a big eater so gobbles things up so you'll have macres at the tissue level gobbling things up they can also seed various tissues and become sort of like Sentry cells and become dendritic cells as well so you can also have monocytes become dendritic cells which also act like macrophases okay so that's the monocytes mono meaning one sight cell so it's just got this one intracellular component when it's stained that's what it looks like all right what else are we left with the myoid progenitor cells can also produce what we call a Mega cararo Blast now Mega Car blast really big right turns into a mega cararo site Mega cararo site more mature and this is a big sound what it does this is interesting remember that bone marrow It's ability to go into uh the general bloodstream through little holes remember you got capillaries right and there's different types of capillaries you can have little holes you can you know these porous holes and you can have sinusoidal which are bigger ones so these sinusoidal holes right so this Mega caride is like this Big Blob and it throws like an arm out an extension of its cytoplasm and it throws it into the bloodstream what happens is it goes chop chop chop chop chop and what it produces are all these little products and these products are called platelets and so now we have these platelets floating through the bloodstream platelets are also known as thrombos sites thrombo sites and hence this process is called thrombo poesis thrombo pois now this one is going to be called well here we've got mon Mony poesis mono cyto poesis and this one is called uh granular poesis granulo poesis so platelets we know are really important when it comes to blood clotting so when you have a damaged blood vessel platelets come in form a plug but then also release a whole bunch of important chemicals that allow for clotting to occur via the clotting Cascade watch the CL and Cascade hemostasis video for more information all right so these are all the cells and I should say formed elements cuz plets we know are now just broken uh parts of the cytoplasm of a megga Cario site this these are the cells that are made through the process of hematopoesis I want to talk a little bit more about the red blood cells for a second because there red blood cells are obviously really important they carry oxygen they carry carbon dioxide so we need to understand what regulates the process of arthop poesis importantly there's a chemical that does this and this chemical is called EO interestingly it's called arthr potin arthr potin stimulates arthr poesis arthr potin is released by the kidneys weird right you got your kidneys and your kidneys control how many red blood cells you're making hm why why would we relegate the the control of red blood cell production to the kidneys the reason why is because the kidneys must filter blood allthough it must filter 120 Ms per minute regardless of what's happening it must do this so it's always getting a taste and snapshot of the blood so it's a really great way to determine what the concentration is of red blood cells and oxygen so what it does is it's able to taste and measure the oxygen content and if the oxygen content is low it releases EP o EPO travels to the bone marrow binds to receptors right and EPO will bind to receptors on precursor cells and that will stimulate the lineage to go down this particular path to produce more Prothro blasts now once the red blood cell quantity goes up you've got more oxygen carrying capacity that signal is inhibited this is perfect negative feedback and it's controlled by the kidneys and the hormone EPO so I think that is covering the overview of herat poesis and arthro poesis so I hope that makes sense hi everyone Dr Mike here if you enjoyed this video please hit like And subscribe we've got hundreds of others just like this if you want to contact us please do so on social media we are on Instagram Twitter and Tik Tok at Dr Mike todorovich at d r m i k e t o d o r o v i c speak to you soon [Music] d