Mod 2: 1.2.1 Exchange Surfaces and Breathing

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Why do multicellular organisms need specialised exchange surfaces and single-celled organisms do not?
Because they are multicellular they have a smaller surface area:vol ratio. Exchange of substances via direct diffusion is too slow. So a transport system is needed to move substances to and from cells quickly.
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Describe the features of an efficient exchange surface.
Large S/A. Thin (often 1 layer of epithelial cells) = short diffusion pathway. Maintains steep concentration gradient of gases. Good blood supply.
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What are the features of the mammalian lung that adapt it to efficient gaseous exchange?
Many alveoli= large S/A for diffusion. Alveolar epithelium and capillary endothelium, only one cell thick=short diffusion pathway. Good blood supply to alveoli, constantly take 02, bring c02, air always refreshed, maintains concentration gradient.
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What are the roles of each component of the lungs?
Goblet cells-secrete mucus, trap bacteria. Cilia- waft mucus up to throat, swallowed and killed by stomach acid. Elastic fibres- stretch and recoil during ventilation. Smooth muscle- controls diameter of tubes. Cartilage- prevent bronchi collapsing.
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Describe inspiration.
Intercostal & diaphragm muscles contract, ribcage moves up and out, diaphragm flattens increasing vol of thorax, so lung pressure decreases below atmospheric level and air flows into lungs (active process).
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Describe expiration.
Intercostal muscles relax, ribcage moves down and in, diaphragm becomes curved, thorax vol decreases, so air pressure increases (above atmospheric pressure), air forced out of lungs (passive process).
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What is meant by tidal volume and vital capacity?
Tidal vol (TV)- vol of air in each breath, usually about 0.4dm3. Vital capacity- the maximum vol of air that can be breathed in or out.
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How and what can a spirometer measure?
An 02 filled chamber (movable lid), subject breathes into tube, lid moves up&down, movement recorded by pen attached to lid, writes on rotating drum, creates spirometer trace (Soda lime-c02) Reads tidal vol, vital capacity, breathing rate & 02 uptake
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What are the precautions of using a spirometer?
Mouth piece must be sterilised. Medical grade 02 must be used. People with asthma can't use them. Can't be done for long periods of time- vol of gas decreases, air breathed out=mix of 02+c02, c02 absorbed by soda lime, only 02 left (respiration).
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Other cards in this set

Card 2

Front

Describe the features of an efficient exchange surface.

Back

Large S/A. Thin (often 1 layer of epithelial cells) = short diffusion pathway. Maintains steep concentration gradient of gases. Good blood supply.

Card 3

Front

What are the features of the mammalian lung that adapt it to efficient gaseous exchange?

Back

Preview of the front of card 3

Card 4

Front

What are the roles of each component of the lungs?

Back

Preview of the front of card 4

Card 5

Front

Describe inspiration.

Back

Preview of the front of card 5
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