The human body is an amazing piece of machinery—with a few weird quirks. I t's amazing how efficiently it works and when some things break down it has the ability to fix itself. Your mouth produces about one litre of saliva each day. Your brain is sometimes more active when you’re asleep than when you’re awake. Laid end to end, an adult’s blood vessels could circle Earth’s equator four times! Bodies give off a tiny amount of light that’s too weak for the eye to see. You lose about 4kg of skin cells every year! Your left lung is about 10 percent smaller than your right one. The lung on the left side of your body is divided into two lobes while the lung on your right side is divided into three. The left lung is also slightly smaller, allowing room for your heart. The largest muscle in your body is the...