Also known as pulmonary ventilation, air is inhaled through the nose and mouth. It makes its way to the lungs through the larynx and pharynx and then it is exhaled through the same passageway.
Creation of Sound
When you exhale, air passes through the larynx which moves the arytenoid cartilages which push the vocal chords together. This makes them vibrate, which creates sound.
Gas Exchange
Oxygen is exchanged for carbon dioxide. This takes place through the alveoli. (This is explained more on the "Gas Exchange" page.)
Olfaction: Smelling
As air enters nasal cavity, chemicals in the air activate the cilia which is the stimulus that sends a signal to the brain. Eventually, the signal reaches the olfactory area of the cerebral cortex, which causes the sensation of smell.
Protection
Protects respiratory surfaces from dehydration and invasion from pathogens.