Topic 3B: Gas Exchange In Humans Flashcards

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1
Q

Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake. [2]

A
  1. Large(r) organisms have a small(er) surface area:volume;
  2. Overcomes long diffusion pathway
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2
Q

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them. [3]

A
  1. Many alveoli provide a large surface area so diffusion is fast;
  2. Many capillaries provide a large surface area so diffusion is fast;
  3. Alveolar epithelium and capillary endothelium are both one cell thick and these cells are flattened so short diffusion pathway;
  4. Ventilation of air and circulation of blood maintain oxygen concentration gradient.
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3
Q

If alveolar epithelium cells die inside a human body they are replaced by non-specialised, thickened tissue.

Explain why death of alveolar epithelium cells reduces gas exchange in human lungs. [3]

A
  1. Reduced surface area;
  2. Increased diffusion pathways;
  3. Reduced rate of gas exchange
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4
Q

Describe the gross structure of the human gas exchange system. [2]

A
  1. Trachea, bronchi, bronchioles, alveoli.
  2. Above structures named in correct order
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5
Q

Describe how humans breathe in and out. [5]

A

Breathing in:
1. Diaphragm (muscles) contract and diaphragm flattens;
2. External intercostal muscles contract and rib cage pulled up/out;
3. (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric pressure);

Breathing out:
4. Diaphragm (muscles) relaxes and diaphragm moves up;
5. External intercostal muscles relax and rib cage moves down/in;
6. (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric pressure).

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6
Q

Describe and explain one feature of the alveolar epithelium that makes the epithelium well adapted as a surface for gas exchange. [2]

A
  1. Flattened cells;
  2. Reduces diffusion pathway
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7
Q

Tidal volume is the volume of air inhaled or exhaled during a single breath when a person is resting.

Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli. [3]

A
  1. Less carbon dioxide exhaled;
  2. (So) reduced concentration gradient (between blood and alveoli);
  3. More carbon dioxide stays in the blood.
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8
Q

Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. Details of breathing are not required. [4]

A
  1. Trachea, bronchi, bronchioles;
  2. Oxygen moves down pressure gradient;
    .
  3. Diffuses down concentration gradient;
  4. Across alveolar epithelium;
  5. Across capillary endothelium.
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9
Q

Describe the pathway taken by an oxygen molecule from an alveolus to the blood. [2]

A
  1. (Across) alveolar epithelium;
  2. Endothelium of capillary.
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10
Q

Describe and explain the mechanism that causes lungs to fill with air. [3]

A
  1. Diaphragm (muscle) contracts and intercostal muscles contract;
  2. (Causes volume increase and) pressure decrease;
  3. Air moves down a pressure gradient.
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11
Q

Scientists who investigate disease may look at risk factors. What is a risk factor? [1]

A
  1. Something that increases the probability of getting a disease.
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12
Q

Suggest two precautions that need to be taken when finding a sample for an experiment. [2]

A
  1. Large sample size;
  2. Individuals chosen at random;
  3. Are healthy;
  4. Equal number of males and females
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13
Q

The volume of air a person can breathe out in 1 second decreases after the age of 30.

Use your knowledge of ventilation to suggest why. [1]

A
  1. Internal intercostal muscles less effective
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