When carbon dioxide dissolves in water, it reacts with the water to produce carbonic acid. The major function of the respiratory system is to supply the body with oxygen and get rid of carbon dioxide. Respiration is the overall exchange of gases between the air you breathe, your blood, and the cells of your body. External respiration is the gas exchange between the air sacs of the lungs and the blood. The cardiovascular system uses blood as the transporting fluid.
Internal respiration is the gas exchange between the blood and tissue cells.
The nasal cavities lie inferior to the cranium and superior to the mouth. Each day, the goblet cells secrete about a quart of sticky mucus. The ciliated cells create a gentle current that moves contaminated mucus back toward the throat, where it is swallowed. The mucus also moistens the air as it is inhaled. A rich supply of capillaries are located in the connective tissue layer of the nasal cavity's mucous membrane.