Answer:
(a)
Diagram A shows inhalation and diagram B shows
exhalation. (1)
(b) Nostrils nasal cavitypharynx larynx
tracheabronchibronchioles alveoli
(1)
(c) The alveolar air pressure in diagram B would be higher
than 760 mmHg. During exhalation, the ribs move downwards and inwards,
decreasing the volume of the thoracic cavity. This causes the lungs to be
compressed and increases the air pressure in the lungs.
(d) The alveoli are numerous, which provides a large surface area for
gaseous exchange. The walls of alveoli are thin (only one-cell thick), which allows
gases to diffuse across easily. The walls of the alveoli are lined with blood
capillaries, which maintain the concentration gradients needed for the
diffusion of gases.
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