4.2 - Gas Exchange in Mammalians

Question 1

What are the gas exchange surfaces for humans?

Answer 1

alveolus

Question 2

How are mammals ventilated?

Answer 2

• consists of inspiration and expiration

INSPIRATION
- external intercostal and diaphragm muscles contract
- causes the ribcage to move upwards and outwards and the diaphragm to flatten which increases the thorax volume
- when volume increases and pressure decreases
- causes air to flow into the lungs
- this is an active process

EXPIRATION
- external intercostal and diaphragm muscles relax
- the ribcage moves downwards and inwards so the diaphragm becomes curved again
- thorax volume decreases which causes air pressure to increase
- air is forced out of the lungs
- normal expiration is a passive process

Question 3

explain the airflow and the gas exchange system

Answer 3

• as you breathe in, air enters the trachea
• the trachea splits into two bronchi and one bronchus leading to each lung
• each bronchus then branches off into smaller tubes called bronchioles
• the end of the bronchioles is small ‘air sacs’ called alveoli where gases are exchanged

Question 4

adaptations

Answer 4

• alveoli are thin and one cell thick allowing for short diffusion pathways
• rich blood supply which maintains the concentration gradient
• there is a moist surfactant to allow gases to dissolve and prevent the alveoli from collapsing

Question 5

Explain how having many alveoli increases the efficiency of the diffusion in the lungs.

Answer 5

increases the surface area to volume ratio

allows for more O2 to enter the capillaries