Respiratory Physiology

  • The primary functions of the lungs are to add oxygen to the blood and remove carbon dioxide from it. To do so, the lungs provide an enormous surface in which oxygen-poor and carbon dioxide-rich venous blood can come into extremely close contact with a oxygen-rich and carbon dioxide-poor alveolar space. Passive diffusion then results in movement of oxygen into the blood from the alveolar space as well as simultaneous movement of carbon dioxide in the opposite direction. By modulating the rate and intensity of respiration, the lungs can exert powerful control on the tension of oxygen and carbon dioxide in the alveoli and in consequence the tension of these gases in the systemic blood.
  • We discuss the basic mechanisms by which the lung operates and how it regulates arterial blood gases in the following sections. It should be pointed out that through its modulation of arterial carbon dioxide tension, the lungs exert powerful regulatory control on the pH of arterial blood; however, this aspect of respiratory physiology is discussed under Acid-Base Physiology