Lungs (Gas Exchange In Humans)

Question 1

What happens when you breathe

Answer 1

1. Breathe in, air enters trachea
2. Trachea splits into 2 bronchi
3. Each bronchus branches odd into smaller tubes - bronchioles
   4, bronchioles end in small air sacs called alveoli
4. rib cage, intercostal muscles and diaphragm all work together to move air in and out

Question 2

Inspiration

Answer 2

1. External intercostal and diaphragm muscles contract
2. Rib cage move up and out and diaphragm flatterns
3. Increase volume in thorax
4. Lung pressure decreases
5. Air flow in from high to low
6. Active , requires energy

Question 3

Expiration

Answer 3

1. external intercostal and diaphragm muscles relax.
2. The ribcage moves downwards and inwards + diaphragm becomes curved again.
3. volume of thorax decreases
4. causing the air pressure to increase (to above atmospheric pressure).
5. Air is forced down the pressure gradient and out of the lungs.
6. Normal expiration is a passive process — it doesn’t require energy.
7. Expiration can be forced though (e.g. if you want to blow out the candles on your birthday cake)

Question 4

Forced expiration

Answer 4

During forced expiration,

• the external intercostal muscles relax
• internal intercostal muscles contract
• pulling the ribcage further down and in. During this time, the movement of the two sets of intercostal muscles is said to be antagonistic (opposing).