FUNCTIONS OF THE RESPIRATORY SYSTEM
Studying, sleeping, talking, eating, and exercising all involve breathing. From our first breath at birth, the rate and depth of our breathing are unconsciously matched to our activities. Although we can voluntarily stop breathing, within a few minutes we must breathe again. Breathing is so characteristic of life that, along with the pulse, it is one of the first things health professionals check to determine if an unconscious person is alive.
Respiration includes the following processes: (1) ventila-tion, or breathing, which is the movement of air into and out of the lungs; (2) the exchange of oxygen (O2) and carbon dioxide (CO2) between the air in the lungs and the blood; (3) the transport of O2 and CO2in the blood; and (4) the exchange of O2 and CO2 between the blood and the tissues. It can be confusing to hear the term respirationalone because sometimes it also refers to cellular metabolism, or cellular respiration; in fact, the two processes are directly related. Breathing provides the O2 needed in cellular respiration to make ATP from glucose.
Breathing also rids the body of potentially toxic CO2, the waste produced during cellular respiration. In addition to respiration, the respiratory system performs the following functions:
1. Regulation of blood pH. The respiratory system can alterblood pH by changing blood CO2 levels.
2. Voice production. Air movement past the vocal cords makessound and speech possible.
3. Olfaction. The sensation of smell occurs when airbornemolecules are drawn into the nasal cavity.
4. Innate immunity . The respiratory systemprotects against some microorganisms and other pathogens, such as viruses, by preventing them from entering the body and by removing them from respiratory surfaces.