6.8 - Exchange of gases in the lungs

Question 1

Where is the site of gas exchange in mammals

Answer 1

• the epithelium of the alveoli

Question 2

Describe the structure of the alveoli

Answer 2

• minute sacs (100-300 micrometers in diameter)
• Situated in the lungs

Question 3

How is the alveoli adapted for its role

Answer 3

• Red blood cells are slowed as they pass through pulmonary capillaries, allowing more time for diffusion
• The distance between the alveolar air and red blood cells is reduced as the red blood cells are flattened against the pulmonary capillary walls
• The walls of alveoli and capillaries = very thin and therefore has a short diffusion pathway
• Alveoli and pulmonary capillaries have a very large SA
• Breathing movements constantly ventilate the lungs, and the action of the heart constantly circulates blood around the alveoli = BOTH ENSURES: steep concentration gradient that is maintained for gas exchange
• Blood flow through the pulmonary capillaries maintains a concentration gradient

Question 4

State a correlation shown in the diagram

Answer 4

Correlation between the incidence of lung cancer in men and number of cigarettes smoked per day

Question 5

Explain why the information provided does not show a casual relationship with the correlation you have identified

Answer 5

• There is no experimental evidence in the data provided to show that smoking causes cancer
• Hence there is no causal link between the 2 variables

Question 6

List 5 factors associated with lung disease

Answer 6

• smoking
• air pollution
• genetics
• infections
• occupation

Question 7

Use the diagram to determine what % of non-smokers are likely to survive to age 80

Answer 7

Anywhere from between 50-60%

Question 8

Calculate how many times greater is the likelihood of a non-smoker living to age 70 than someone who smokes over 25 cigarettes a day

Answer 8

• 2x
• around 80% of non-smokers live to age 70
• whereas around 40% of people who smoke more than 25 cigarettes a day live to 70

Question 9

How is lung function measured

Answer 9

• Forced Expiratory Volume (FEV)
• it is the volume of air that can be forcibly blown out in 1 second, after full inspiration

Question 10

Suggest how pulmonary fibrosis might effect FEV and explain why

Answer 10

• FEV will be lower/less because to achieve a normal FEV, the lungs must be elastic
• fibrosis reduces elasticity and makes it difficult to breathe out

Question 11

Suggest some restrictions that have been put in place in order to reduce lung disease

Answer 11

• restrictions on production of cigarettes = less tobaccos smoked = less incidences of lung disease
• banning smoking in public spaces = reduces opportunity for smokers to smoke = less tobacco smoked = less incidences of lung disease
• ban on tobaccos advertising = less encouragement for people to smoke tobacco, especially younger people
• age restrictions on buying tobacco = prevent young people starting to smoke and becoming addicted
• plain packaging = reduces appeal of tobacco
• health warnings on packets = educate/persuade people on the dangers of smoking = aims to stop smoking altogether

Question 12

What is the risk factors associated with emphysema

Answer 12

Smoking
—> impossible to diagnose until lungs are irreversibly damaged

Question 13

What are the consequences of emphysema

Answer 13

• elastin becomes stretched out so air cannot be forced out of lungs
• SA of alveoli is reduced reduced — very little gas exchange
• breathlessness due to lack of oxygen

Question 14

What are the symptoms of emphysema

Answer 14

• shortness of breath (due to loss of elasticity and reduced oxygen levels)
• chronic cough (body trying to remove damaged tissue + cilia is destroyed)
• bluish skin colouration (low oxygen levels)

Question 15

What are the risk factors associated with asthma

Answer 15

• stimulated by allergens (e.g. pets, pollution, cold air, etc)
• allergens cause WBC which produce histamines

Question 16

For a person who suffers from asthma, what do histamines cause

Answer 16

• lining of lungs to become inflamed
• cells of epithelium lining secrete large quantities of mucus
• fluid leaves capillaries and enters airways
• muscle surrounding bronchioles contracts and so constricts the airways

Question 17

What are the symptoms of asthma

Answer 17

• difficulty in breathing (constriction of bronchi and bronchioles)
• wheezing (air passing through constricted bronchi and bronchioles
• tight feeling in chest (cannot ventilate lungs adequately)
• Coughing (reflex response to obstructed airways)

Question 18

What are the risk factors associated with COPD

Answer 18

• smoking
• air pollution
• genetic makeup
• frequent chest infections
• occupations — chemicals, gases, dust exposure

Question 19

What are the main symptoms of COPD

Answer 19

• increasing breathlessness, particularly when you’re active
• a persistent chesty cough with phlegm - some may dismiss this as just a “smoker’s cough”
• frequent chest infections
• persistent wheezing

Question 20

What does pulmonary fibrosis cause

Answer 20

• Scars form on the epithelium of the lungs
• Become irreversibly thickened - oxygen can’t diffuse into blood as efficiently
• diffusion pathway lengthened - lungs contain reduced air volume
• reduced lung elasticity

Question 21

What are the symptoms of pulmonary fibrosis

Answer 21

• shortness of breath (volume of air space is taken up by fibrosis tissue)
• Chronic, dry cough (fibrosis tissue causing an obstruction)
• pain + discomfort in chest (fibrosis tissue causes excess pressure in the lungs)
• weakness or fatigue (reduced intake of oxygen = less energy from respiration)