For Students
What would your body be like without bones? Bones give your body shape, help you move, protect your organs, and more! On this page, you can learn about bones, what happens when they get hurt, and how to keep them healthy.
What are bones?
Bones are the tissues—groups of cells that work together—that make up your skeleton. Bones might remind you of dead things or fossils, but the bones in your body are alive. They grow and change all the time!
Bones keep your body healthy in many ways. They:
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- Support and hold up your body. Without bones your body would be a squishy blob on the ground.
- Help you move. Muscles work together with bones to move your body around.
- Protect your organs. Some bones shield your organs from injury. For example, your ribs protect your heart and lungs, and your skull protects your brain.
- Make blood cells. Some types of bone have a jelly-like material inside called bone marrow (MEH-row). New blood cells are made inside the bone marrow!
- Store energy. Some types of bone, like the leg bones, contain cells that store fat and release it when your body needs energy.
- Store minerals and vitamin D. Bones can store minerals like calcium and phosphorus, and vitamin D, and release them when your body needs them.
What are bones made of?
Bones are made mostly of a protein called collagen (KAA-luh-jn) and a mineral called calcium phosphate (KAL-see-uhm FAA-sfayt). Together, these materials make your bones strong and flexible.
Bones have three layers:
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- The periosteum (peh-ree-ow-STEE-uhm) is a thin membrane covering the bone that contains nerves and blood vessels.
- Compact bone is the dense and hard outer layer of the bone that you see when you look at a skeleton.
- Cancellous (KAN-suh-luhs) bone is inside the compact bone. It is full of holes and looks a little like a sponge. Bone marrow fills in the holes of the sponge.
Bones are held together at the joints by ligaments (LI-guh-muhnts), a type of tissue that is like a strong rubber band. Learn more about joints, which are made up of ligaments and other types of tissue.
Activity
Try this experiment at home to learn what makes bones strong and flexible at the same time! Be sure to wash your hands with soap and water after touching the bones!
How do bones grow?
As you get older and grow taller, your bones grow, too! There are special zones of bones that grow with you called growth plates.
Did You Know?
A baby is born with about 300 bones. Many of them eventually fuse (grow together) to form the 206 bones that adults have.
Bone tissue is constantly changing in a process called remodeling. All the time, old or damaged bone tissue is broken down, and new bone tissue is made to replace it. When you’re young, new bone is made faster than old bone is broken down, which means that your bones get denser and stronger. In most people, the amount of bone tissue in the skeleton peaks by their mid- to late 20s.
- The bone cells that break down old bone are called osteoclasts (AA-stee-uh-klasts).
- The bone cells that make new bone are called osteoblasts (AA-stee-uh-blasts).
As you age, old bone tissue is broken down faster than new bone is made. For some people, the bones become weaker and easier to break. This condition is called osteoporosis (aa-stee-ow-opr-OW-suhs).
Activity
Doctors have special names for the ways bones can break. Learn about the different types of fractures with this activity!
What happens when bones break?
Broken bones are also called fractures (FRAK-chrz). The break can go through only part of the bone or completely through it.
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It hurts to break a bone! There might also be swelling and bruising. If you are injured and go to the doctor, the doctor may take pictures of your bone with x-rays to see if it is broken. If you do have a broken bone, the doctor may put on a cast, splint, or brace to keep the bone from moving around as it heals, and to make sure it heals correctly. Sometimes, bones move so much when they break that the doctor has to “set the bone”—put it back in the right place before putting a cast, splint, or brace on it.
Activity
How much force does it take to break a bone? Try this experiment at home with chicken bones to find out!
Most broken bones heal within a few months. First, your body forms a blood clot around the break to protect it and deliver the cells that will heal it. Next, a healing zone called a callus (KA-luhs) forms around the break. It joins the bones together. At first, the callus is soft, but it gets harder and stronger as the bone heals.
What is scoliosis?
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Your backbone, also called your spine, is actually made of many small bones called vertebrae (VUR-tuh-bray) that form a line. Scoliosis (skow-lee-OW-suhs) happens when the spine bones are curved instead of being straight.
Did You Know?
Most of the time, people get scoliosis as pre-teens or teenagers. By going to the doctor and getting treated when needed, people with scoliosis can have healthy, active lives.
Small curves usually don’t cause problems. If a doctor notices you have a curved spine, they may just check it every once in a while, to make sure the curve doesn’t get worse. Really big curves or small curves that get worse can cause health problems. In these cases, doctors treat scoliosis with a back brace or surgery.
Doctors don’t know what causes scoliosis, but they do know that having a parent who had scoliosis makes it more likely that you will have it, too.
How can I help keep my bones healthy?
Avoid bone injuries.
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Wear the right equipment to protect your bones. Always wear a helmet to protect your skull while biking, scootering, skateboarding, or skating. You can also wear elbow and knee pads to protect your arms and legs.
When playing sports like football, soccer, lacrosse, or ice hockey, always wear all the right equipment. Make sure the safety gear fits you, or else it might not do its job.
When you’re in the car, remember to buckle your seatbelt.
Exercise.
Get plenty of physical activity every day. Your bones respond to exercise by making new bone tissue, which helps keep them strong.
To keep bones healthy, do activities that put weight on your bones. Playing basketball, kickball, walking, jumping rope, and dancing are good examples.
Eat well to keep your bones healthy.
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Calcium and vitamin D. Remember that bones are made of a mineral called calcium phosphate? To keep bones strong, you need to get that calcium from food or supplements. You can get calcium from milk, cheese, and yogurt. Leafy green vegetables like broccoli, brussels sprouts, and kale are also important sources of calcium.
Vitamin D helps your body absorb the calcium in the foods you eat. You can get vitamin D from certain foods, like eggs, fish, and special types of orange juice, milk, and cereals that have vitamin D added to them.
Eat a balanced diet. Try to eat a combination of fruits, vegetables, whole grains, lean protein, and low-fat dairy. Eating a variety of foods and being active every day helps keep your body healthy and strong. While you need both muscle and fat for your body to work properly, in general, having more healthy muscle tissue helps keep your bones healthy.
Vocabulary
Bone marrow (MEH-row). A jelly-like material inside some types of bones. New blood cells are made inside the bone marrow.
Bone remodeling (ruh-MAA-duh-luhng). A process where old or damaged bone tissue is broken down, and new bone tissue is made to replace it.
Calcium phosphate (KAL-see-uhm FAA-sfayt). A mineral, along with a type of protein called collagen, that make up bones. Calcium phosphate helps make bones hard and strong.
Callus (KA-luhs). A healing zone that forms around a broken bone and helps join the bone pieces together.
Cancellous (KAN-suh-luhs) bone. The bone layer inside the compact bone. It is full of holes and looks a little like a sponge.
Cells. The smallest building blocks of life. Your body is made of trillions of cells!
Collagen (KAA-luh-jn). A type of protein, along with a mineral called calcium phosphate, that make up bones. Collagen helps make bones flexible and strong.
Compact (KUHM-pakt) bone. The smooth and hard outer layer of the bone that you see when you look at a skeleton.
Fractures (FRAK-chrz). Broken bones.
Growth plates. Special zones of bones that grow with you.
Ligaments (LI-guh-muhnts). Tissues that hold bones together.
Membrane. A thin sheet of tissue that acts as a boundary or lining.
Mineral. Solid substances made in nature, but not by living things, that can help your body grow and stay healthy.
Organ. A part of the body that has a specific job.
Osteoblasts (AA-stee-uh-blasts). The bone cells that make new bone.
Osteoclasts (AA-stee-uh-klasts). The bone cells that break down old bone.
Osteoporosis (aa-stee-ow-opr-OW-suhs). A condition that some people get when they age, where old bone tissue is broken down faster than new bone is made, which can make the bones weaker and easier to break.
Periosteum (peh-ree-ow-STEE-uhm). A thin membrane covering the bone, which contains nerves and blood vessels.
Proteins. Large chains of molecules made by living things and essential to life. There are many different types of proteins, and proteins do several different jobs. For example, they provide structure for the cell and can also help important chemical reactions happen in the body.
Scoliosis (skow-lee-OW-suhs). A condition that happens when the spine bones are curved instead of being straight.
Supplement. A substance that a person can add to their diet to make sure they get all the nutrients their body needs.
Tissues. Groups of cells that work together.
Vertebrae (VUR-tuh-bray). Small bones arranged in a line that form your backbone, also called your spine.
