What happens to your diaphragm when you breathe in?

When you breathe in, also known as inhalation, your diaphragm contracts and moves downward. This increases the space in your chest cavity, into which your lungs expand. The intercostal muscles between your ribs also help enlarge the chest cavity. They contract to pull your rib cage both upward and outward when you inhale. As your lungs expand, air is sucked in through your nose or mouth. The air travels down your windpipe and into your lungs. After passing through your bronchial tubes, the air finally reaches and inflates the tiny sacs called alveoli. This is where the oxygen in the air you've inhaled is passed into the bloodstream and carbon dioxide is passed from the bloodstream into the alveoli to be exhaled.