Why do multicellular organisms need specialised exchange surfaces?
Too many cells so diffusion distance is too large to reach all cells. Too high metabolic demands. SA:V ratio is too low.
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What are the features of an efficient exchange surface?
Small diffusion distance, High SA:V ratio, good blood supply, ventilation.
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Describe the structure and function of the trachea.
Lined with goblet cells and cilia to produce a moist surface and trap debris and toxins. Incomplete rings of cartilage to give flexibility and to prevent collapse.
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Why are the alveoli such good exchange surfaces?
Very high surface area due to folding. Squamous cells give small diffusion distance. Network of capillaries to keep concentration gradient high.
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Explain the role of the diaphragm in inhalation and exhalation.
Inhalation - Diaphragm contracts and squashes to increase the volume of the thorax and decrease the pressure to cause air to rush in. Exhalation - Relaxes in the dome position to force air out of the thorax by increasing pressure and lowering volume.
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Give a difference between the bronchus and the bronchioles.
Bronchioles have no cartilage, much smaller, they have smooth muscle and elastic fibres.
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When do the external intercostal muscles contract?
During inspiration / breathing in.
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Why is ventilation important?
To ensure the concentration of oxygen in the air is higher than in the blood and that the concentration of co2 is higher in the blood to encourage diffusion.
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Outline the use of a spirometer
Measures oxygen uptake. Lid moves up and down to produce a graph.
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What is the role of the soda lime in a spirometer?
To absorb the co2.
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What is advantageous about countercurrent flow?
It maintains a favourable concentration gradient and does not reach equilbrium.
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Outline the mechanism of gaseous exchange in bony fish.
Mouth open & operculum close. Buccal floor lowers to increase the volume and decrease the pressure. Mouth closes. Buccal flow raises to increase pressure and decrease the volume. Operculum opens and water is pushed out over gills.
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What makes gills and efficient surface for gas exchange?
Large surface area due to two rows of gills filaments per gill. Filaments are folded into lamellae. There is a short diffusion distance and a network of capillaries.
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How does air enter the tracheae in an insect?
Through pores called spiracles.
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What is the function of tracheal fluid?
To reduce the surface area so that cells are not over supplied with oxygen.
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Outline two methods that active insects can adopt to increase their oxygen intake?
Flexible walls which act as air sacs which can encourage expansion and contraction of thorax. Wings can also alter the volume of the thorax during flight.
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Why are insects limited in size?
Their ventilation system can only supply a certain amount of cells and being too large would decrease SA:V ratio and increase diffusion distance as well as increasing oxygen demand and a higher amount of co2 would need to be removed.
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Other cards in this set
Card 2
Front
What are the features of an efficient exchange surface?
Back
Small diffusion distance, High SA:V ratio, good blood supply, ventilation.
Card 3
Front
Describe the structure and function of the trachea.
Back
Card 4
Front
Why are the alveoli such good exchange surfaces?
Back
Card 5
Front
Explain the role of the diaphragm in inhalation and exhalation.
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