Video - Breathing 101: The Journey of Air in Your Body

Air enters through the nose, passing through the nasal cavity, which filters, moistens, and warms it. It moves through the pharynx, which further filters it and protects against infection, then through the open epiglottis into the trachea. The trachea branches into bronchi, leading to the lungs, and subdivides into bronchioles ending in alveoli. In the alveoli, oxygen enters the bloodstream via capillaries. The diaphragm controls breathing by expanding the lungs for inhalation and contracting them for exhalation.