Your heart is really a muscle. It's located a little to the left of the middle of your chest, and it's about the size of your fist. There are lots of muscles all over your body in your arms, in your legs, in your back, even in your behind. But this muscle is special because of what it does the heart sends blood around your body. The blood provides your body with the oxygen it needs. It also carries away the waste that your body has to get rid of.