nose and pharynx

Nose:
external nose nasal cavity

Functions:passageway for air, cleans the air, humidities, warms air, smell
along with paranasal sinuses are resonating chambers for speech

Pharynx: common opening for digestive and respiratory systems
Three regions: nasopharynx, oropharynx, laryngopharynx

composition of Air

The composition of normal, dry, atmospheric air is 20.95% oxygen, 0.03% carbon dioxide and 78.08% nitrogen. The normal atmospheric pressure at sea level is about 76 mmHG. the total pressure exterted by a gas mixture is equal to the sum of pressures exerted by each constituents gas ( Dalton's law)

pO2= 159.2 mmHg
pCO2= 0.003 mmHg
pN2=600.6 mmHg

Atmospheric pressure increases markedly underwater.