- [Voiceover] Like every other system, there's problems of disease and disorders that go with the skeletal. Probably one of the most common is going to be a sprain. Now sprains are stretched or torn ligaments. So it's not really the bone being damaged but it's what holds the bones together. If you end up stretching out a ligament too far or even partially tearing it, it will not be able to perform the original function. If you completely tear it then all bets are off. Bursitis and tendinitis, both of these are going to be inflammations. Bursitis is when a bursa becomes inflamed. Now a bursa is going to be this fluid-filled sac found in your joints. Its purpose to help to cushion and can help protect some of the components of the joints. So bursitis inflammation. Tendinitis also inflammation, but is now when a tendon has become inflamed. Arthritis. There are many different types of arthritis. It's not just one single, here is arthritis. But in general all the various types of arthritis deal with inflammation of joints, whether it's minor inflammation, major inflammation something is causing a problem. Some examples are Osteoarthritis, Rheumatoid arthritis. Now Rheumatoid's kind of interesting because in Rheumatoid arthritis it's your body's own cells attacking your body's joints. Your own immune cells are attacking the joints causing inflammation and damage in Rheumatoid arthritis. Now we have Osteoporosis. Osteoporosis is characterized by excessive bone loss. You can see the figure on the right is figure A. That is healthy bone. The figure on the left that is figure B, that is Osteoporotic bone. You can see how in the Osteoporotic bone you have all these little opens, or channels or holes in there. It's making the bone that much weaker. That means the Osteoclast cell is working faster than the Osteoblast cell. So Osteoporosis the calcium's being pulled out of the bone making the bone weaker. Now what's the most common age group or gender to have this? Unfortunately the most common grouping is going to be post-menopausal females. Because of all the hormone changes going on, those hormone changes upset the balance of the bones causing the bones to have excessive bone mass loss. So losing mass that losing strength and the bones can get progressively weaker.