Muscles are bundles of fibres that tense and relax to move different parts of the body.
Bones are the hard parts that anchor the muscles.
Your senses supply the brain with a constant stream of information about your surroundings. There are over 200 bones in the body. They not only anchor the muscles but support skin and other tissue, and protect your heart, brain and other organs from damage. Bones are very tough and light because they are made from a mixture of hard minerals, such as calcium, and stringy elastic collagen . Inside the tough casing of minerals and collagen, bone is like a sponge, with holes containing special cells called o steocytes .