List of top Science Questions on Respiration

Give reason for this: Rings of cartilage are present in the throat.
Give reason for this: Fine hair and mucus are present in the nasal passage.
During respiration, exchange of gases occurs in:
atmospheric air is being passed

In the experimental set-up shown above in diagram (I) atmospheric air is being passed into lime water with a syringe while in diagram (II) air is being exhaled into lime water. The time taken for the lime water to turn milky in both the test tubes is different. Give reason.
Sometimes while running, athletes suffer from muscle cramps. Why? How is the respiration in this case different from aerobic respiration?