 So today we're going to go over bone tissue and specifically we're going to talk about the bone cells So I wanted to remind you that bone tissue just like all connective tissue is going to have a ground substance fibers and then cells the bone tissue the hard bone tissue is As you recall made out of a ground substance called hydroxy appetite but that is mostly calcium carbonate and A phosphate together so the ground substance is mostly the mineral part of the bone and This part of the bone if it gets if there were too much of it the bone might actually be a little bit Crumbly, but it makes the bone hard that matrix that minerals makes it more hard the fibers of the bone as you recall our collagen and Those fibers actually make the bone more flexible so that it doesn't crush all the time It actually makes it more flexible So together this makes up the the strength of the bone tissue so as We get older though we get more of the ground substance and less of the collagen which is what can cause some osteoporosis the cells then of the bone tissue there's several of them there's osteogenic cells which actually are more like stem cells and they produce the osteoblasts which are the young cells that help to build bone but also help to repair bone as well and Then those will actually mature into osteocytes so these three Primary cells and then there's a fourth cell that I'm going to go over with you as well so I have a picture to share with you about the cells and I wanted to make sure you remember that the cells are actually housed Inside the bone but underneath that periosteum that's around the bone and then underneath the endosteum that's inside the bone So recall that under the periosteum there's going to be cells that can actually help grow the bone and The beginning cell that we talked about the osteogenic cell is also called the osteoprogenitor cell You might see in some areas some places These are the stem cells. So these will actually Start out growing some of the other cells. They'll divide and grow into some of the other cells So the osteogenic cells help to generate some of the other osteo osteonic cells these osteogenic cells will Develop into the young osteoblasts and I call these are builders It helps me to remember that be there in the word that these are osteoblasts. These are the builders You see it forms the bone matrix these osteoblasts are underneath the periosteum and Will actually bring in the calcium and the phosphate from the bloodstream and deposit it into the bone itself So these will help in bone deposition Depositing the calcium and the phosphates the minerals from the bloodstream. So these are our builders as these mature They actually will change into an osteocyte. So these are the mature cells these help to maintain the bone tissue And what happens is the osteoblasts bring in the minerals and the calcium They actually end up getting surrounded by this matrix And so the osteocytes are inside the matrix. You see them housed here on the picture of the bone Inside the compact bone in those concentric circles of lamellae Also, the osteocytes will then be housed inside a little sack called a lacuna If you recall the cartilage cells were also housed in a sack called a lacuna You don't see it here in this picture, but the osteocytes are held in there So again the osteogenic cells or the stem cells they'll also develop into these builders the osteoblasts Which will mature into the osteocytes which are encased inside the matrix The fourth type of cell is this osteoclast over here And the osteoclast are actually from a different origin. They originate from the White blood cells and the macrophages This osteoclast I call them the cutters So you see the difference there is that C in that word So calling them the cutters helps me to remember that these will literally cut away at the bone and will send the calcium and the phosphate back into the bloodstream To help with muscle contractions and the heart muscle and all the other uses that is needed in the body of calcium so These osteoclasts will barely cut away a little bit of the calcium at the time. This is called resorption Resorption is just cutting away at the bone a little bit and again sending those minerals out into the bloodstream This is not reabsorption the cell is not reabsorbing the calcium. It's actually cutting it away So these osteoclasts are A little bit like this scrubber Okay, as it resorbs the bone. It's kind of like Resorbing the bone is kind of like this scrubber on the board just taking a little bit of the surface away You see how it doesn't just scrub into the board, right? It just takes a little bit of the surface away So it's just going to take a little bit of that calcium off of the bone and send it back into the bloodstream So that's what the osteoclasts do So those are the bones of the cells of the bone tissue. Sorry the cells of the bone tissue Osteogenic osteoblasts osteocytes and then the cutters the osteoclasts