Question

how doe the diagram help in breathing

Answer 1

hey mate its diaphragm not diagram.
Diaphragm's Role in Breathing. When the diaphragm contracts and moves lower, the chest cavity enlarges, reducing the pressure inside the lungs. To equalize the pressure, air enters the lungs. When the diaphragm relaxes and moves back up, the elasticity of the lungs and chest wall pushes air out of the lungs.

Answer 2

The diaphragm contracts when we breathe in.

The diaphragm also moves downwards

This increases space in the lung cavity.

To occupy that space the air comes in and enters our body through the nose.

Thus in this way diaphragms help in breathing.

Hope it helps you.