welcome to this short tutorial today that I'm going to be doing with you on the cells involved in bone formation now this is just a basic introduction to these cells and their roles within the sceletal system and before we take a look at the three specific types I'm going to highlight this picture right here of a mesenchimal stem cell in relation to the sceletal system we also refer to it as an osteoprogenitor cell now the reason I bring up this type of cell is because it's important to always remember that our cells don't just come from nowhere stem cells need to be given instructions as to which type of cell is required within the body and then they will specialize kind of like what you will do as you learn more and more so they are cells which can become many different uh cell types and this is why they are so heavily studied within medicine so just writing there that they have the capability to become many different cell types and these mesenchimal stem cells here are going to differentiate within our sceletal system into an Osteo blast which will later differentiate in into osteocytes so we'll start with the osteoblast up here and our Osteo site down here just a bit lower so what I'm going to do here so we can visualize it a bit better is draw a little bit of a picture to show what's going on now our Osteo blasts make new bone and our osteocytes regulate existing bone within the body and to show this let's just draw just a cross-section of a little bit of bone here so we've got the osteoblast sitting on top of the bone surface and we have the osteocytes down lower sitting within the bone matrix now our osteoblasts are going to be secreting osteoid and regulating its calcification and as those osteoblasts secrete that osteoid and regulate the calcification some of the osteoblasts are going to become trapped and those osteoblasts that become trapped within the bone matrix are going to differentiate further into those osteocytes so you can see them here trapped within that bone matrix as part of the process of differentiation the osteocytes are going going to develop long cytoplasmic extensions which Aid in supplying nutrients to the existing bone so we're just showing here that all this area around the osteos site is calcified bone all right now just quickly so we know exactly what's going on let's quickly uh write down and take a note of what's happening with these two cells and what they do so we really remember it now as the osteoblast deposit that new bone some are going to become trapped in that bone matrix as they become trapped they're going to differentiate into osteocytes and Supply nutrition to the Bone just while I finish writing that down we can start to think of these two different cells in relation to what they're doing and simplify it our osteoblasts are the construction workers and the osteocytes are the maintenance guys within the glal system I'll give you a bit of time quickly to think about what we could possibly need apart from construction and maintenance within bone while I'm writing these two descriptions down so have a think about that quickly before we talk about our last cell type so we can see with the ostero blast there that they're just sitting on top of that bone surface and they're going to be depositing the new osteoid and it will be in response to demand so uh the thickening of bone when our bones need to be uh thickened those osteoblasts are going to deposit that new osteoid and Aid in its calcification okay so we have our osteoblasts and osteocytes which are going to be derived from our mesenchimal stem cells but what about this last type down here that I just discussed they're going to be known as our osteoclasts now our osteoclasts are a fosic cell of the sceletal system a AIC meaning they're going to be involved in bone degradation so it's going to be eroding existing bone something also important for us to notice here is that this particular cell type comes from the maccrage monotic cell line which is responsible for producing many cells within the body which have roles involved in breakdown of tissue and ingestion of foreign particles so it can erode and cycle bone matrix as with all things in the body we want to maintain a healthy homeostasis or equilibrium between our deposition and degradation so the Osteo class will work in conjunction with our osteoblast in response to hormone stimulus to maintain calcium homeostasis within the body they also alter their activity based on mechanical stress such as a tennis player whose serving arms bone will thicken over time due to increased stress and the resulting increased deposition of bone by osteoblasts so our osteoclast and osteoblast are going to be working together to maintain our bone shape and Bone strength okay so just to wrap up everything that we've learned so far in this tutorial we'll take a quick look at the identifying features of these cells as as if we were looking at them under a microscope now our osteoblasts have a single nucleus and they will be performing their job on the surface of bone we will occasionally see them a little bit deep to the surface but these are more than likely in the process of differentiating into osteocytes our Osteo sites being of the same cell line are also mononucleate but they're def finding feature is these long cytoplasmic extensions we can see here that will stretch out uh to increase the area to which they can supply nutrient to that bone matrix so cytoplasmic projections and also single nucleus our last type that osteoclast they are a very large cell they're going to be much larger than the osteoblasts and the osteocytes and they have many nuclear nues within them so they are multinucleate so large and multinucleate and with that we can wrap up our introduction to the cells of bone formation I hope this has been helpful and allowed you to get a better grasp on the concept thanks for watching guys and see you next time