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state 3 ways inwhich the structure of the lungs allow efficent gas exchange
Original post by Rohan007best
state 3 ways inwhich the structure of the lungs allow efficent gas exchange

walls of alveoli very thin only 1 cell thick- short diffusion distance
alveoli covered in surfactant- stops lungs collapsing
large number of small alveoli- creates large surface area to volume ratio for diffusion
Original post by ewapieczykolan
walls of alveoli very thin only 1 cell thick- short diffusion distance
alveoli covered in surfactant- stops lungs collapsing
large number of small alveoli- creates large surface area to volume ratio for diffusion

Hi good answer - 2 marks out of 3 [sorry!] - surfactant does stop lungs collapsing correct, but does not actually increase efficiency of gas exchange so would not be in mark scheme.

3rd mark is for:
EITHER:
rich blood supply to alveoli with intricately branched capillaries ----> large surface area

OR:
red cell diameter [7 micrometres] is very similar to internal diameter of capillaries -----> RBCs move slowly -----> time for gas exchange + reduced distance to diffuse

OR:
regular breathing brings in fresh O2 ----> conc-n gradient maintained -----> efficient diffusion

M

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