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20. The human respiratory system includes epiglottis, trachea, bronchi, bronchioles, alveoli,
pleural membranes, ribs, intercostal muscles, diaphragm. These are involved in two
functions: ventilation an d exchange of gases.

Lungs are enclosed within the Thorax , an air tight cavity
At the base of the thorax is a sheet of…

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two pleural membranes surround the pleural cavity membranes will secrete
pleural fluid which acts as a lubricant , reducing friction between the lungs and
the ribcage.
goblet cells of the cilliated epithelium that produces this mucus. Mucus is a slimy
solution of mucin, which is glycoproteins with many carbohydrate chains…

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24. Plants rely entirely on diffusion for the exchange of gases. Leaves are therefore thin to
shorten distances for diffusion and have a large surface area and are permeated by air

Plants photosynthesise during the day and respire at night.

the leaf is thin and flat with a large…

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28. Light can pass through to the spongy mesophyll. The spaces between mesophyll cells
allow carbon dioxide to diffuse to the cells and oxygen can diffuse away. The cells are moist
so gases can dissolve.
29. Leaves have a cuticle to prevent water loss which also reduces gaseous exchange.

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