 Hey everybody, Dr. O here. I want to talk about the skin on and in your bones called the periosteum and endosteum here. So the periosteum is going to be this connective tissue skin on the outside of your bones. This is, it's going to help the collagen fibers are going to help actually attach bone to other tissues like the joint capsules and tendons and these kind of things. So it's very important there, but as pre three primary functions, it does isolate bone from surrounding tissue. So it's the skin that goes around the outside of the bone. A number two, it does provide a route for nerves and blood vessels. There's actually a lot of pain fibers in the periosteum, which is why like a hairline fracture where this gets torn, especially kind of jagged Lee can be so painful. Sometimes a hairline fracture can cause more pain than a, than a complete compound fracture can. It also plays a role because as you see there, the periosteum is going to be right next to, and there's going to be some bone cells here. So it plays a role in bone growth and bone repair. We'll learn about bone growth later, but if there's a fracture, the osteocytes in this area can actually become osteoblast and participate in, in bone repair. So those are going to be the primary functions of the periosteum. Just think skin around your bones. We covered a couple of chapters ago that this is dense, irregular, connective tissue. The endosteum is going to be the skin that lines the inside of your bones and the, and especially your spongy bone here. It's incomplete. It's an incomplete layer, but it does have a lot of these bone cells. The osteoprogenitor cells, your bone stem cells, osteoblasts, et cetera. So it plays a large role in bone growth and repair, but we generally don't talk about that as much. So the periosteum thinks skin on the outside of the bone. Endosteum, this incomplete skin on the inside of bone, and they both play a role in providing nutrition to bone, playing a role in bone growth, repair, and protection. All right. I hope this helps. Have a wonderful day. Be blessed.