Gaseous exchange

Question 1

Inspiration process ( Active process)

Answer 1

External intercostal muscles contract, lifting rib cage upwards and outwards
Diaphragm contracts and flattens, increasing thorax volume and decreasing lung pressure
Lung pressure lower than atmospheric, causing air to rush in
Oxygen diffuses into capillaries from alveoli

Question 2

Expiration process (largely passive process)

Answer 2

Internal intercostal muscles contract, pulling rib cage down and inwards
External intercostals relax
Diaphragm relaxes into dome shape, lowering thorax volume and increasing lung pressure
Lung pressure greater than atmospheric
Carbon dioxide rushes out of lungs into atmosphere