Breathing is an active process To exhale Relaxation of external intercostal muscles diaphragm > return of diaphragm, ribs, sternum to resting position >restores thoracic cavity to preinspiratory volume>increases pressure in ungs→> air is exhaled Air OutBreathing is an active process ◼ To exhale – Relaxation of external intercostal muscles & diaphragm → return of diaphragm, ribs, & sternum to resting position → restores thoracic cavity to preinspiratory volume → increases pressure in lungs → air is exhaled