How do the diaphragm and rib muscles help with breathing? These muscles pull lungs down to draw in air
change the air pressure
open up the air flow tubes
keep food out of the chest
push blood around the lungs

When you breathe in, or inhale, your diaphragm contracts and moves downward. This increases the space in your chest cavity, and your lungs expand into it. The muscles between your ribs also help enlarge the chest cavity. They contract to pull your rib cage both upward and outward when you inhale