Human gas exchange & repiration

Question 1

Inspiration

Answer 1

• diaphragm contracts & flattens
• external intercostal muscles contract
• internal intercostal muscles relax
• rib cage moves upwards & outwards
• volume of chest cavity increases
• air pressure inside lings decreases
• air flows into lungs

Question 2

Expiration

Answer 2

• diaphragm relaxes ; dome-shaped
• external intercostal muscles relax
• internal intercostal muscles contract
• rib cage move downwards & inwards
• volume of chest cavity decreases
• forces air out of lungs

Question 3

Adaptations of alveoli for gas exchange

Answer 3

1) alveolar wall is 1-cell thick ; reduce distance for diffusion of gases ; faster rate of diffusion

2) concentration gradient for gases remains steep due to continuous variation & blood flow

3) provide large SA : vol ratio ; faster rate of diffusion
4) O2 dissolves in moist lining inside alveoli

Question 4

Pathway of O2 -> blood

Answer 4

• O2 in inhaled air from nostril -> nasal cavity -> pharynx ->larynx -> bronchus -> bronchioles -> alveoli

Question 5

What happens in alveoli