1. Why do you think the heart is behind the lungs and not between them?
2. Do you know what protects your lungs? (Ans: ribcage)
3. Your lungs are not muscles. They are like sponges. They fill up like balloons when you breathe in.
Your diaphragm is a muscle underneath your lungs. When you breath, the diaphragm goes down, drawing air into your lungs like a vacuum cleaner. When the diaphragm moves up, it squeezes the air out of your lungs, the way you'd squeeze water out of the sponge.