Question

Expiration involves

Relaxation of diaphragm and intercostal muscles
Contraction of diaphragm and intercostal muscles
Contraction of diaphragm muscles
Contraction of intercostal muscles

Answer 1

relaxation of diaphragm and intercoastal muscles

Answer 2

When you breathe in, or inhale, 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.

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