Erythropoiesis

00:00 Well let us first of all look at erythropoiesis, the lineage that gives rise to our red blood cells. Those very important cells that transport oxygen and carbon dioxide throughout the body within blood vessels. Well, it is important to understand that there are a number of stages in erythropoiesis and again let me stress they arise from the megakaryocyte or erythrocyte progenitor cell. Have a look at the slide on the right-hand side, in one of the most fascinating things when you study histology, You see some very very pretty slides. Very pretty stains, very pretty demonstrations of tissue. I think bone marrow is one of the prettiest tissues to look at using standard stains under the light microscope. Well, when you look at the slide, you can see some red blood cells that have maintained their mature red blood cells. All those small pink reddish or orange stain structures are erythrocytes. They are matured, they are circulating in the bone marrow and they are leaving the bone marrow to enter into the general circulation.

01:23 They arise from the proerythroblast. This is the very first stage of the progenitor cell then starting to form what would be the final erythrocyte. These proerythroblasts are large cells. They occupy a diameter of up to 20 microns. So they are big cells and one thing to bear in mind is particularly when you look at lineages of this cell and the neutrophil later on is have a think about what the end product is going to be.

02:04 The end product is going to be the red blood cells that you see also in this image.

02:08 They are much smaller cells, they are only about 6 to 8 microns in diameter. So when the progenitor cell gives rise to a proerythroblast, it is a large cell that is eventually going to go through the differentiation process and finally end up being just a little package of hemoglobin.

02:31 And that is essentially what a red blood cell is. So when you see these large cells, they represent the very busy activities of these cells and I will refer to that as we go through this lineage. The proerythroblast has a mild amount of basophilia. Suddenly the progenitor cell has given rise to the proerythroblast. It is going to now start, going through the process of making hemoglobin. But initially they just has a mild amount of basophilia.

03:12 Well the next stage in the process of forming a red blood cell is differentiating into what we call the basophilic erythroblast and that is shown on this particular cell here. And basically if you look very carefully in the cytoplasm, there is stronger basophilia that you saw previously in the proerythroblast. And then again as I said earlier think back as to what the destination of the cell is going to be. It is going to be a red blood cell. It is going to be containing a whole lot of hemoglobin, the protein carrying oxygen.

03:55 So initially, back in the early cell stages, you would expect to have a cell that develops an enormous amount of rough or granular endoplasmic reticulum to make that protein hemoglobin.

04:11 So at some stage and that's stage you see here, the cell has accumulated all this endoplasmic reticulum, which takes up the basophilic stain. So here is an indication now that this cell has been activated to start making hemoglobin. It has a factory now to make that hemoglobin.