Inspiration:
1) Internal intercostal muscles relax, external contract so ribcage goes up and out
2) Diaphragm contracts and goes down3) Lung volume increases, air pressure inside decreases
4) Air is hence forced into the lungs

Exhalation:
1) External intercostal muscles relax, internal contract, ribcage moves down and inward
2) Diaphragm relaxes and moves back in3) Lung volume decreases, air pressure inside increases
4) Air is hence forced out

Alveoli:
Where gas exchange in the lungs happens. Features include:
-Thin walls (1 cell thick)
-Large surface area
-Moist surface
-Many blood capillaries