Friday, April 24, 2009

PULMONARY VENTILATION


The process of gas exchange in the body, called respiration, has three basic steps :

  1. Pulmonary ventilation (pulmon- = lung), or breathing, is the inhalation (inflow) and exhalation (outflow) of air between the atmosphore and the alveoli of the lungs.
  2. External (pulmonary) respiration is the exchange of gases between the alveoli of the lungs and the blood in pulmonary capillaries across the respiratory membrane. In the process, pulmonary capillary blood gains O2 and loses CO.
  3. Internal (tissue) respiration is the exchange of gases between blood in systemic capillaries and tissue cells. In this step the blood loses O2 and give off CO2 during the production of ATP are termed cellular respiration .

In pulmonary ventilation, air flows between the atmosphere and the alveoli of the lungs because of alternating pressure differences created by contraction and relaxation of respiratory muscles. The rate of airflow and the amount of effort needed for breathing is also influenced by alveolar surface tension compliance of the lungs, and airway resistance.

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