載入中... 相關課程 Back A Voyage to Mars: Bone Loss in Space 登入觀看 ⇐ Use this menu to view and help create subtitles for this video in many different languages. You'll probably want to hide YouTube's captions if using these subtitles. A Voyage to Mars: Bone Loss in Space : Why do bones get weaker with less gravity and how can we prevent bone loss in space? 上傳學習單 下載學習單 相關課程 0 / 750 A voyage to Mars: bone loss in space The ultimate goal for human space flight is sending a human to Mars. It's not an easy task though. The journey to Mars takes about six months, Then, astronouts would spend about two years on the surface, before making their six month journey back to Earth. A trip like this has serious consequences to the human body. Especially your bones. Your bones? But why? Living in less gravity causes your bones to break down and become weaker. That doesn't make sense. Astronauts travel in space all the time. Right? Yes, but they lose one to two percent of their bone per month. Why do bones get weaker with less gravity? And how can we prevent bone loss in space? On earth, we are adapted to one G of gravity pulling us toward the center of the planet. On a mission to Mars, a total of one year of the trip would be spent in weightlessness. Astronauts could lose between twelve to twenty-four percent of their bone. Then, once the astronaut reaches Mars, they would be living in forty percent of the Earth's gravity. We don't even KNOW how much additional bone they will lose. Every time you take a step, jump, or flex a muscle, you put stress on your bones. That stress damages them, and causes tiny microfractures. Don't worry, this is a good thing. In fact, your body was built to handle the impact, and fix the microfractures. To fix the problem, your body sends in a cell called an osteoclast, to go in and eat away the damaged bone. When the osteoclast is done, new cells called osteoblast rebuild the bone back up. This process is called remodeling, and in the end, your bone is healthier than they were before. In space, without gravity to cause the microfracture, the process of remodeling is altered. Osteoblast do less building, and osteoclast seem to eat away more bone. As a result, your skeleton isn't as healthy as when you left earth. Not all bone loss is equal though. The most change happens in the weight-bearing part of your body, like the lower spine, hips, legs, and feet. No one knows exactly why. Maybe your body thinks your bones are overbuilt, or maybe gravity affects osteoblast and osteoclast. But either way, the shape of your bone changes, and not for the better. If you look at the crosssection of your bone, this constant eating and rebuilding causes the shape to change.