• Lungs have a specific function in line with their function.
• The lungs contain alveoli which increase the surface area for gaseous exchange.
• The rate of diffusion is increased because alveoli consist of very thin walls and a high concentration gradient is maintained.
• Pulmonary ventilation = ventilation rate x tidal volume
• Lungs ventilate themselves due to thoracic movement which is controlled by the diaphragm and intercostal muscles.
• Air always moves from an area of high pressure to an area of low pressure.
• Pulmonary tuberculosis is caused by a reduction in lung surface area due to the break down the alveoli
• Pulmonary fibrosis is a restrictive lung disorder caused by an increase in fibrous connective tissue.
• Asthma is a chronic inflammatory disease in which allergens trigger an inflammatory response causing bronchoconstriction.
• Emphysema is a progressive lung disease which causes a break down in the lungs’ structure.

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TEST IT!

1.

One disease that can be caused by breathing in asbestos fibres is asbestosis. The fibres enter into the bronchioles and the alveoli, destroying phagocytes and causing the lung tissues to scar and become fibrous. The elasticity of the lungs is reduced due to the fibrous fibre and the walls of the alveoli thicken. The reduction in gas exchange causes sufferers to experience a shortness of breath.

a) Why could would the lungs become more susceptible to infections with less phagocytes?

b) How would a reduction in lung elasticity cause breathing to become more difficult?

c) A reduction in elasticity will reduce the efficiency of gas exchange. What other changes in the lungs will do this?

2.

Lungs are adapted to allow the rapid exchange of oxygen between the blood in the capillaries and the air in the alveoli.

a) Explain how.

b) What is meant by tidal volume?

c) Pulmonary fibrosis is a restrictive lung disease. How does it reduce lung volume?

3.

The volume of air in the lungs of two people was measured. One was healthy and one was suffering from emphysema. The results are in the table below.

a) Both people were exhaling. How do the results support this claim?

b) What’s the evidence that person B has emphysema?

c) How does emphysema reduce the rate of gaseous exchange in the lungs?

ANSWERS

1.

a) The phagocytes engulf pathogens and other microorganisms that enter the lungs which may otherwise cause disease.

b) The lung capacity will be reduced and breathing out becomes particularly hard. The rate of oxygen diffusion is decreased

c) Answers include:

i. thickening of the alveolar walls
ii. a longer diffusion pathway
iii. scarred or fibrous tissue
iv. a reduction in surface area for gaseous exchange

2.

a) Answers include:

i. The lungs contain many alveoli which increase the surface area for gaseous exchange

ii. There’s a large network of capillaries to transport the oxygen from the alveoli to the bloodstream

iii. There’s a short diffusion distance between the alveoli and the capillary walls

iv. A diffusion gradient is maintained

b) Tidal volume is the amount of the air which is inhaled and exhaled in one breath.

c) The effect of this disease is an exchange of the lung’s parenchyma with the fibrotic tissue. This decreases the amount of oxygen that can be taken in by the lungs.

3.

a) The volume of air decreases.

b) There’s more air left in the lungs after exhalation.

c) Answers include:

i. The alveoli collapse so that there are fewer left

ii. The epithelium walls thicken

iii. The surface area of the lungs decreases

iv. The rate of diffusion decreases

v. There’s a loss of elasticity due to less elastin

vi. The flow rate is reduced

vii. the concentration gradient is reduced so the rate of diffusion is slower