Brain
The Brain is the main operation that tells your body what to do. It sends brainwaves to different parts of the body. The brain is the most important part of your body. Without your brain, YOU WOULD BE A SCARECROW. The BRAIN MAKES YOU grow, think, and move. Your Brain has different parts. One of those parts is the memory bank. Sometimes when you're unconscious you can lose your memor, it may take a long time to get it back.
Bones
Without bones you wouldn't be able to stand, walk, or run. Bones are made of soft, flexible material called cartilage. By the time your born, most of the cartilage has hardened and turned into bone. New bone tissue is always making new tissue. Bones are a storing places for minerals up until your 35. There are new bones being made than there are breaking down. Weak bones break down more easily so old people break their bones.
Muscles
When you make a face, like a smile or a frown, you use a lot of muscles just to make that little movement.