3: EXCHANGE SYSTEMS AND MASS TRANSPORT - HUMAN GAS EXCHANGE + VENTILATION

Question 1

Describe the structure of the human gas exchange system

Answer 1

• as you breathe in air enters the trachea
• the trachea splits into 2 bronchi (1 bronchus leading into each lung)
• each bronchus branches off into smaller tubes called bronchioles which end in small air sacs called alveoli where gas exchange occurs
• the ribcage, intercostal muscles and diaphragm all work together to move air in and out of the lungs

Question 2

Describe the process of inspiration

Answer 2

• external intercostal muscles contract, internal intercostal muscles relax
• ribcage moves upwards and outwards
• diaphragm contracts and flattens
• volume of thoracic cavity increases
• lung pressure decreases below atmospheric pressure
• air enters lungs down pressure gradient

Question 3

Describe the process of expiration

Answer 3

• both sets of intercostal muscles relax
• ribcage moves downwards and inwards
• diaphragm relaxes and curves upwards
• volume of thoracic cavity decreases
• lung pressure increases above atmospheric pressure
• air moves out of lungs down pressure gradient

Question 4

Describe the process of forced expiration

Answer 4

• internal intercostal muscles contract, external intercostal muscles relax
• ribcage moves downwards and inwards
• diaphragm relaxes and curves upwards
• volume of thoracic cavity decreases
• lung pressure increases above atmospheric pressure
• air forced out of lungs down pressure gradient

Question 5

Is inspiration an active/passive process and why?

Answer 5

• active
• external intercostal muscles contract

Question 6

Is expiration an active/passive process and why?

Answer 6

• passive
• both sets of intercostal muscles relax

Question 7

Is forced expiration an active/passive process and why?

Answer 7

• active
• internal intercostal muscles contract