“Bones support your body and allow you to move. They protect your brain, heart, and other organs from injury.
Bone is a living, growing tissue. It is made mostly of two materials: collagen (KOL-uh-juhn), a protein that provides a soft framework, and calcium (KAL-see-uhm), a mineral that adds strength and hardness. This combination makes bone strong and flexible enough to hold up under stress.
Bone releases calcium and other minerals into the body when you need them for other uses.
Think of your bones as a “bank” where you “deposit” and “withdraw” bone tissue. During your childhood and teenage years, new bone is added (or deposited) to the skeleton faster than old bone is removed (or withdrawn). As a result, your bones become larger, heavier, and denser.”
National Institute of Arthritis and Musculosketetal and Skin Disease (https://www.niams.nih.gov/health-topics/kids/healthy-bones)