Dirt particles and pathogens such as bacteria and viruses get stuck in the mucus in the trachea and bronchi. The cilia lining the tubes beat and move the mucus up away from the lungs and into the throat where it is swallowed.
b)Explain why smokers are at a higher risk of developing infectious diseases in the breathing system than non-smokers?
Tobacco smoke anaesthetises the cilia and stops them beating. The mucus along with the pathogens stuck in it is no longer moved away from the bronchioles and the lungs, so the risk of them becoming infected increases.
c)Explain why smokers are more at risk of developing emphysema (COPD) than non-smokers. Why are people affected by emphysema often breathless as soon as they do any physical exercise?
Emphysema is a condition when the structure of the alveoli of the lungs breaks down, leaving much larger air sacs. People affected become breathless as soon as they do any physical exercise because the surface area available for gaseous exchange is much reduced, so they cannot get the oxygen needed to supply energy through aerobic respiration in their cells.