All right. We're going to continue our discussion of the skeletal system and any time I start a new organ system, I like to talk about the functions because it really gives you an understanding of why we're learning this organ system and then it will follow along as we actually develop more of the details. So when we think about the skeletal system, a lot of times we think about it as a support system. It keeps us upright, particularly when we're talking about Homo sapiens. It allows for us to stay in bipedally and on two legs. So it is that. That's one of the main functions. It's a structural framework but importantly one thing I want to talk about, we'll talk about this in great more detail when we are talking about the individual bones, is in terms of as an attachment point. So you're going to have these ligaments and these tendons actually attaching to certain parts of the bone. So muscle tendons particularly when you have these big bumps associated with bone, these are going to be attachment points. So when you have the muscle attached there, it'll contract and allow for movement to occur. Additionally, it's going to protect certain other internal organs. So the two main ones that you think of, you think of your skull, that calvaria or skullcap protecting the brain. You think of your rib cage or thorax protecting your lungs as well as your heart. It's also important to think about areas where you don't have as much bone protection. So if you think of your abdomen, you don't have any bones right here in the anterior part of your abdomen. So you have to have other structures that are serving to protect those areas. So really important in terms of the muscles as well as the tendons in those areas protecting. All right. Hugely important in terms of the skeletal system: assistance and movement. So if you think about those attachment points and where they're actually attaching onto the bone, that muscle contracts, that's going to move the bone. So when the muscle contracts, the muscle shortens. It will pull on the bone allowing for movement to occur. Now, this is more important, and when you think about how the bones actually structured, you're going to have certain areas that are completely hollow in bone that's filled in with fat etc. You'll have other parts of the bone that are not quite as heavy. This is allowing for that ease of movement. So very important in terms of that. So the three that I just mentioned in terms of the functions are what we all typically think of when we think of the skeletal system, but there's other functions that are just as important and particularly in terms of keeping homeostasis within the body. So one of the main ones is mineral storage and release, and we all have heard drink your milk, get that calcium into your bones because bone is going to store 99 percent of the calcium in your body. But calcium's important in other areas of the body as well. So you'll have calcium sometimes released into the blood in order to allow for your gastrointestinal tract to function properly. So calcium can be released from bone to allow for homeostasis to keep up. So we'll talk about different ways and different glands. So in terms of your thyroid gland and your parathyroid glands, that will help keep certain amounts of calcium within the bone or release it if need be. Phosphorus is another mineral that's stored within the bone, not as quite as high amounts as calcium, but it will play a role in terms of mineral release and storage as well. Now, bone is also important in terms of hemopoiesis, and you'll talk about this a lot more with Dr. Fox when you talk about his blood lecture, but actually within the bone, within the red bone marrow, you're going to have blood cell production. So all types of blood cell production, red blood cells, white blood cells etc and that's going to be formed within red bone marrow. So, juvenile bones, so when I say the term juvenile, I mean a sub-adult or a young individual. Juvenile bones are going to have huge amounts of red bone marrow. As you move into adulthood, there's only going to be certain areas of bone that are actually going to form red blood cells. So if we talk about epiphyses, these are going to be the ends of long bones and then in certain other bones such as your os coxa or hip bones, certain areas in terms of the ribs in adulthood will still form these red blood cells. As you move into adulthood, a lot of that red bone marrow is differentiated into yellow bone marrow, and yellow bone marrow is what we think about when we think about marrow. It's that fatty tissue that's actually within the hollow portions of the bone. So that's going to make up the majority of the bone marrow found in adults. It's important in terms of triglyceride storage so that fatty storage as energy storage for these yellow bone marrow.
