Gas Exchange in Humans

Question 1

Lung structure (+ function)

Answer 1

• Trachea, bronchi, bronchioles (oxygen moves down pressure gradient)
• Many alveoli and capillaries (large surface area)
• Alveoli and capillaries with thin epithelium (short diffusion distance for oxygen)
• Internal and external intercostal muscles (allow ribs to move)

Question 2

What is ventilation?

Answer 2

Brings in air with a high concentration of oxygen and replaces air with a low concentration of oxygen, maintaining a steep concentration gradient

Question 3

Inspiration

Answer 3

• Diaphragm contracts and flattens
• External intercostal muscles contract, ribs move up and out
• Increased volume of the thorax
• Decreased pressure in the thorax
• Air moves down pressure gradient

Question 4

Expiration

Answer 4

• Diaphragm relaxes and becomes domed
• Internal intercostal muscles contract, ribs move down and in
• Decreased volume of the thorax
• Increased pressure in the thorax
• Air moves down pressure gradient
• During forced expiration, internal and external intercostal muscles move as antagonistic pairs

Question 5

Pulmonary ventilation equation

Answer 5

Pulmonary ventilation = tidal volume x breathing rate

Question 6

What is circulation?

Answer 6

Replacing blood high in oxygen with blood low in oxygen, maintaining a steep concentration gradient

Question 7

Examples of lung diseases

Answer 7

• TB (tubercles and fibrosis reduce tidal volume)
• Fibrosis (thick scar tissue reduces tidal volume)
• Asthma (inflamed airways reduce forced expiratory volume)

Question 8

Risk factors for lung disease

Answer 8

• Tobacco
• Passive smoking
• Pollutants (sulphur dioxide)