human gas exchange Flashcards
Explain how downward movement of the diaphragm leads to air entering the lungs.
Increases volume (in lungs / thorax);
Context must be lungs / thorax
Ignore space increases
- Lowers pressure (in lungs / thorax);
Accept lungs / chest expand
Ignore reference to ‘change in pressure’
- Air (pushed) in by higher outside pressure / down pressure gradient;
CONTEXT MUST BE FOR THE LUNGS
Describe how oxygen in air in the alveoli enters the blood in capillaries.
Diffusion;
Accept down diffusion gradient
- Across (alveoli) epithelium / (capillary) endothelium;
You could use curve A to find the total volume of air that this person could breathe out in one complete breath. Describe how. from graph
Extend / extrapolate curve / graph;
- (Read off where) it flattens / reaches maximum / peaks;
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.
Many alveoli / alveoli walls folded provide a large surface area;
Neutral: alveoli provide a large surface area
- Many capillaries provide a large surface area;
- (So) fast diffusion;
Neutral: greater / better diffusion
Neutral: fast gas exchange
Allow ‘fast diffusion’ only once
- Alveoli or capillary walls / epithelium / lining are thin / short distance between alveoli and blood;
Reject: thin membranes / cell walls
Accept: one cell thick for ‘thin’
- Flattened / squamous epithelium;
Accept: endothelial
- (So) short diffusion distance / pathway;
- (So) fast diffusion;
- Ventilation / circulation;
Accept: descriptions for ventilation / circulation
- Maintains a diffusion / concentration gradient;
- (So) fast diffusion;
Several diseases are caused by inhaling asbestos fibres. Most of these
diseases result from the build up of these tiny asbestos fibres in the lungs.
One of these diseases is asbestosis. The asbestos fibres are very small and
enter the bronchioles and alveoli. They cause the destruction of phagocytes
5 and the surrounding lung tissue becomes scarred and fibrous. The fibrous
tissue reduces the elasticity of the lungs and causes the alveolar walls
to thicken. One of the main symptoms of asbestosis is shortness of breath
caused by reduced gas exchange.
People with asbestosis are at a greater risk of developing lung cancer. The time
10 between exposure to asbestos and the occurrence of lung cancer is 20–30 years.
Apart from reduced elasticity, explain how changes to the lung tissue reduce the efficiency of gas exchange.
Alveolar walls thicken;
Longer diffusion pathway;
Scarred / fibrous tissue;
Reduces surface area (for gaseous exchange);
Describe the difference in the composition of gases in inhaled and exhaled air. Explain how these differences are caused.
inhaled air contains more oxygen than exhaled air;
2 inhaled air contains less carbon dioxide than exhaled air;
3 inhaled air contains less water (vapour);
4 relative amount / percentage of nitrogen also changes;
5 respiration results in lower blood oxygen / higher blood carbon dioxide;
6 oxygen enters blood / carbon dioxide leaves blood in alveoli;
7 by diffusion;
8 water vapour diffuses from moist surface;
Describe the movement of the ribs when a person breathes in
up and out;
Name the type of cells in the alveoli
Epithelium
A large number of small alveoli is more efficient in gas exchange than a smaller number of larger alveoli. Explain why.
(Small alveoli with) large surface area;
For diffusion;
Just before a person starts to exhale, the composition of the air in an alveolus differs from the composition of the air in the trachea.
(i) Give two ways in which the composition would differ.
- ____________________________________________________________
- ____________________________________________________________
(1)
(ii) Explain what causes this difference in composition between the air in the alveolus and the air in the trachea.
Less oxygen / more carbon dioxide / more water vapour;
Two differences required, but only one mark for this part
of the question.
1
(ii) Gas exchange takes place in alveoli / does not take place
in trachea;
Suggest why blood returning to the heart from the lungs contains some carbon dioxide.
Concentrations reach equilibrium / become equal;
Diffusion occurs when there is a concentration gradient
(so some will remain in blood);
OR
Lung cells / vessel cells respire;
Add / produce carbon dioxide;
here is a greater percentage reduction in blood flow to the diaphragm than to the lungs during a dive. Explain the advantage to a diving seal of
(i) blood continuing to flow to the lungs;
______________________________________________________________
______________________________________________________________
(1)
(ii) a large reduction in blood flow to the diaphragm.
Some oxygen still in lungs (which will enter the blood) /
removal of carbon dioxide (from blood);
1
(ii) More blood available for other organs;
Supplying oxygen / glucose / removing carbon dioxide;
OR
Diaphragm muscles not contracting (as not breathing);
Will not require (as much) oxygen / glucose;
Cells A and B are biconcave discs. Explain one advantage of a biconcave disc over a spherical cell of the same volume in transporting oxygen.
____________________________________________
Large (surface) area;
For diffusion;
or
Short distance to centre of cell / to all haemoglobin;
For diffusion;
