 Hey, everybody, Dr. O here. Let's talk about the four different types of bone cells. So first of all, bone cells only make up about 2% of bone tissue. Most of it's going to be your protein collagen and it's going to be your minerals, especially calcium. But there are four types of bone cells, but I'm going to show you that there's really only two. We'll get there in a second. Let's start with the osteogenic cell. I call this the osteoprogenitor cell. Either way, it is a stem cell, a bone stem cell. So a cell that can make new bone, it can make other things too. But osteoprogenitor cells make new bone and here's how they do so. If you need to build bone, let's say you're building bone from an embryonic cartilage skeleton in your mother's womb or you're repairing a fracture or bones are going in some way, these osteogenic stem cells or these osteoprogenitor cells will become osteoblasts. Osteoblasts build bone. They take calcium from the environment and they put it into your bone. So remember that blasts build bone, osteoblasts build bone. So once an osteoblast has basically encased itself in bone by adding all this mineral all around it, an osteoblast then becomes an osteocyte. So an osteocyte, word means bone cell, this is a mature bone cell. It's going to be the cell that maintains the tissue. So notice that an osteoprogenitor cell made an osteoblast that became an osteocyte. That's why I say that even though there's four types of bone cells, these three are really just one continuum. It's really cool. Osteoprocytes maintain bone. That's their primary function, but they can help repair damaged bone. They can actually become, they can revert back to being an osteoblast or even an osteoprogenitor cell. So pretty cool. So osteoprogenitor cells are bone stem cells, osteoblasts build new bony matrix. Osteocytes are mature bone cells that maintain it. The other type of cell is the osteoclast. So osteoclasts as you can see they look a little different. These are giant cells, multi-nucleate cells and their job is to resorb or break down bone. So you would think, why would ever want that to happen? Well, if we need calcium in our blood, our body has to go and get it from our bones. So osteoclasts will take that bone, the calcium from our bones and put it back into our blood, same with other minerals. But you also want to do this. I imagine like remodeling and maintenance of bone, you have to tear down old bones. You can build better bone. I think of like around here we tear down old bridges and build new ones, right? So osteoclasts are not always bad. Too much osteoclast activity though certainly will weaken your bones. Let me talk about that more in nutrition. So osteoclasts break down bone, osteoblasts build bone, osteoprogenitor cells are your bone stem cells and then osteocytes are the mature bone cells. Those are the four different cells that you have to know to understand bone tissue. I hope this helps. Have a wonderful day. Be blessed.