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Uh, Dr. Sonia? Hi, RJ. Come on in. Take a seat. I understand you want to learn more

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about bones, their structure and function. I sure do. I want to be the best cross-country

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runner in my state, and knowing more about my body might actually be an advantage. And

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after meeting Leland Melvin, I want to learn more about astronauts and how their bones

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can be affected by spaceflight. Sure. I'd love to discuss your body's skeletal system

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with you. Students, working in groups, take a few minutes to answer the following questions.

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What does the skeletal system do? It may be helpful to sketch a picture. List some types

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of bones in your body and explain their function. What are some ways to keep your bones healthy?

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How are the skeletal and muscular systems related? It's now time to pause the program.

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Without the skeletal system, your body would collapse. Your skeleton has many functions.

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It provides shape and support, protects your internal organs like your brain, heart, and

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lungs, enables you to move, produces red blood cells, and stores important minerals until

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your body needs them. You have about 206 bones in your body. For example, your arm consists

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of the humerus, radius, and ulna. Your leg consists of the femur, patella, tibia, and

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fibula. All your bones are connected to the vertical column, or backbone, in some way.

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I mentioned earlier that the skeletal system enables you to move. Most of the body's bones

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are associated with muscles. The muscles pull on the bones to make the body move.

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So the muscles and bones in our bodies work as a system?

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That's a great observation, RJ. That's why we can't just learn about muscles without

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understanding about bones, and vice versa. Bones also store minerals, such as calcium

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and phosphorus. These minerals make the bones strong and hard. They're packed tightly together.

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In fact, bones are so strong that they can absorb more force without breaking than concrete

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or granite rock. And bones are much, much lighter.

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Is there anything else in bones besides calcium and phosphorus?

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Yes. Bones also contain living cells and tissues, such as blood and nerves. As you grow, new

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bone tissue is produced. Even after you are grown, your bones continue to form new bone

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tissue. So what does the inside of a bone look like?

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Well, for example, let's look at a femur, or thigh bone. The femur, which is the longest

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bone, connects the pelvic bones to the lower leg bones. Notice the thin, tough membrane

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that covers all of the bone except the ends. Blood vessels and nerves enter and leave the

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bone through the membrane. Beneath the membrane is a layer of compact bone, which is hard

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and dense. Just inside the compact bone is a layer of spongy bone. Spongy bone is found

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in the backbone and at the ends of the bones. Like a sponge, spongy bone has many small

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spaces within it. This structure makes spongy bone lightweight but strong. The spaces in

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bone contain a soft, connected tissue called marrow.

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Because my leg was immobilized for a period of time, does that mean that the bones of

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my leg were affected? Sure your bones were affected, not in terms

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of size, but in terms of bone density. So, RJ, do you have any idea how to keep your

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bones healthy? Well, I believe good nutrition and exercise

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is the key to strong and healthy bones. Way to go, RJ. You're pretty good.

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I learned about good nutrition and exercise from the NASA Connect program. Better health

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from space to earth. Go to the NASA Connect website to learn more.

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You know, RJ, a well-balanced diet contains enough calcium and phosphorus to keep your

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bones strong while they're still growing. Meats, whole grains, and leafy green vegetables

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are all excellent sources of both minerals. Dairy products, including milk, are excellent

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sources of calcium. Exercise is also important to help bones become stronger and denser.

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But you don't have a problem with that because you work out all the time.

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I also learned that it's important to develop good nutrition and exercise habits when you're

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in space. That's true. It's very important because your body's bones are still growing.

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Beth Shepard told me earlier that astronauts' bones become weaker and smaller after they

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return from space. How much do they lose? Well, it depends on a number of factors, such

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as spaceflight duration, amount of exercise in space, nutrition, and body chemistry. Most

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of the bone loss occurs in the lower portion of the body, primarily from weight-bearing

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bones. One study we conducted on astronauts on the ISS showed that the mean, or average,

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bone mineral loss in the hip portion of the femur, or spongy bone, ranged from 1 to 2.5

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percent per month, about 1.35 percent per month in the pelvic region, and 1 percent

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per month in the lower back, or lumbar region. That's really interesting. So what happens

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when astronauts go to Mars and beyond? If an astronaut loses about 1 percent of their

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bone mineral in the lower back per month, then that means that he or she will lose roughly

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12 percent over a year. Since the current missions haven't lasted that long, we don't

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actually know, but it is likely. And therefore, we need to conduct more research to know for

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certain. You know, the more we can learn about how our bodies function in space, the closer

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we get to developing countermeasures that will significantly reduce the effects of bone

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loss and muscle loss while in space. Space research is important because it helps us

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to understand how our bodies function here on Earth. It is another tool to help us combat

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diseases, such as the bone disease osteoporosis. Thanks, Dr. Sonia. If you ever need assistance

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with your research, just call me. I'll do that, RJ, and good luck with your training.

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Okay, take it easy.

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I think we'll be hearing more from RJ in the years to come. And hopefully, we'll be hearing

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more from you. Don't forget to check out this program's Student Challenge, which can be

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found on the NASA Connect website. Well, guys, that wraps up another episode of NASA Connect.

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We'd like to thank everyone who helped make this program possible. Got a comment, question,

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or suggestion? Well, then email them to connect at larp.nasa.gov. So until next time, stay

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connected to math, science, technology, and NASA. And remember, the good stress in life.

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See you then.