AIR PASSES THROUGH
o the upper airways (nose, pharynx, and upper larynx)
o the lower airways (lower larynx, trachea, bronchi, and first generations of bronchioles)
o the lungs (respiratory bronchioles, alveolar ducts, and alveoli).
THE CONDUCTING AIRWAYS SERVE TO MOISTEN AND CLEAN THE AIR:
o Inspired air becomes humidified.
o Particles in the air deposit onto mucus. The trapped particles are then moved to the mouth by ciliary beating, where they are swallowed.
THE RESPIRATORY AIRWAYS SERVE FOR GAS EXCHANGE: OXYGEN MOVES FROM AIR TO BLOOD, WHEREAS WASTE PRODUCTS SUCH AS CO2 MOVE FROM BLOOD TO AIR.
Photo (c) from Bio 301 Human Physiology
· Droplets can form when air rushes in the upper airways during inhalation and exhalation. Analogy: mist on surface of the sea. Healthy mucus doesn’t break up to form droplets.
· When mucus breaks up and forms droplets, the particles (contaminants) that had deposited onto the mucus are released: they can either go into the deep lungs or back into the environment.
· Factors that favor the break-up of mucus include: dry air, dirty air, old age, a poor diet, and bacterial or viral infection. Many of these factors are associated with a weak immune system.