3.1 Exchange surfaces and breathing

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What three main things affect the need for an exchange system?
Size, Surface area to volume ratio, level of activity
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What are three features of good exchange surfaces and give examples of these features?
Large SA e.g. folding and root hair cells, thin barriers to reduce diffusion distance e.g. alveoli and good blood supply to maintain steep conc gradient e.g. in fish gills
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Outline gaseous exchange in the lungs
In the alveoli, O2 passed from the air in the alveoli to RBCs in the capillaries and CO2 passes from RBCs to air in alveoli, steep conc gradients in each direction maintained
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Name some adaptations that reduce the distance gases have to diffuse across
Alveolus wall one cell thick, capillary wall one cell thick, both walls squamous (flattened+thin), capillaries in close conact w/ alveolus, capillaries so narrow erythrocytes squeezed against wall, making them closer to alveolus air
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What is the importance of a good blood supply?
To maintain a steep conc gradient, conc of CO2 higher in blood than alveolus air so can diffuse out, blood transports O2 away lungs so conc of O2 kept lower than alveolus so successfully diffuses into blood
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What components is the human airway made up of, from biggest to smallest?
Trachea branch into the 2 bronchi, branch into bronchioles, end in clusters of alveoli
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What is the structure of the trachea and bronchi?
Similar structure, bronchi just narrower than the trachea. Supported by C-shaped rings of cartilage to prevent collapse but also flexibility
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What is the structure of the bronchioles?
Narrower than bronchi, no cartilage, walls mainly consist of smooth muscle and elastic fibres
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What is smooth muscle?
A type of muscle that contracts involuntarily to make the lumen of the airway narrower to control the flow of air e.g. when there is harmful substances in the air
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What are elastic fibres and how do they work with smooth muscle?
Bundles of protein that provide elasticity and resistance in the airways. Allows dilation of the lumen after constriction by the smooth muscle by recoiling back to their original state (as they get deformed during constriction)
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Where are cartilage be found in the airways?
Trachea and the bronchi
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Where can goblet cells be found in the airways?
Trachea and the bronchi
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Where can smooth muscle be found in the airways?
Trachea, bronchi and the bronchioles
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Where can ciliated epithelium be found in the airways?
Trachea, bronchi and bronchioles
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Where can elastic fibres be found in the airways?
Trachea, bronchi, bronchioles and alveoli
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What happens during inhalation?
External intercostal muscles contract, internal intercostal muscles relax, expanding ribcage upwards+outwards, diaphragm contracts pulling downwards increase v of chest, P inside lungs < atmospheric P, air moves in down P gradient from high to low
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What happens during exhalation?
External intercostal muscles relax, internal intercostal muscles contract, pulls ribcage inwards+downwards, diaphragm relaxes dome shape decreases chest v, P inside lungs > atmospheric P, air moves out down P gradient from high to low
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What is a spirometer and briefly explain how it works
An instrument used to measure air capacity of lungs and the movement of air in and out of the lungs, oxygen tank floating on water, lid moves down as used up, soda lime absorbs CO2 exhaled, allowing measurement of O2 consumption
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What precautions should be taken when using a spirometer?
Subject healthy+asthma free, fresh+functioning soda lime, no air leaks in apparatus (inaccuracy), sterilised mouth piece, water chamber not overfilled, medical grade O2 used in the air chamber
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What is vital capacity and how could it be measured?
The total volume of air that can be moved by the lungs in one break, measured by subject taking deep breath and expelling all air possible from lungs
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What is the residual volume?
The volume of air that remains in lungs even after forced expiration, it stays in airways and alveoli
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What is the tidal volume?
The volume of air moved in/out of lungs in one breath, sufficient to supply O2 required in body at rest
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How would you work out total lung capacity?
Add together vital capacity and residual volume
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What do bony fish use in ventilation, what are they made up of and what is the name of the thing covering them?
Gills, covered by bony protective plate operculum, gills consist of gill filaments attached to a bony arch and gill filaments made up of very numerous lamellae. All richly supplied in blood
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How is the surface area of fish gaseous exchange systems increased?
Each of the gill filaments that make up the gills are made up of lamella which are folds of the filament that greatly increase SA
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How is water passed through the fish?
Water enters buccal cavity (mouth) so P inside buccal cavity < surrounding water so water moves in, closes buccal cavity to increase P so water pushed out over the gills where gaseous exchange occurs
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What kind of flow is used in fish ventilation systems and how is this
Countercurrent flow, involves water and blood flowing in different directions so that favourable conditions for gaseous exchange are provided through the entire exchange surface so max O2 absorbed
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What system of ventilation do insects use, what type is this and what components is this made up of?
Tracheal system, open circ. system made up of: Spiracles-pores along the body, trachea-bigger tubes branch into tracheoles smaller tubes that deliver O2 directly to tissues
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What ways can the rate of diffusion be increased in insects?
Withdrawing tracheal fluid to increase SA as more tracheal wall exposed to air
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Card 2

Front

What are three features of good exchange surfaces and give examples of these features?

Back

Large SA e.g. folding and root hair cells, thin barriers to reduce diffusion distance e.g. alveoli and good blood supply to maintain steep conc gradient e.g. in fish gills

Card 3

Front

Outline gaseous exchange in the lungs

Back

Preview of the front of card 3

Card 4

Front

Name some adaptations that reduce the distance gases have to diffuse across

Back

Preview of the front of card 4

Card 5

Front

What is the importance of a good blood supply?

Back

Preview of the front of card 5
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