Function of the Respiratory System

Definition
The primary functions of the respiratory system are to inhale oxygen through the lungs to be delivered to all parts of the body and to exhale carbon dioxide to remove it from the body. This is accomplished by ventilation and gas exchange.

Ventilation is a mechanical process. Inhalation actively moves the diaphragm down reducing the air pressure within the lungs to inflate the lungs with air.  Exhalation passively moves the diaphragm up increasing the air pressure within the lungs to deflate the lungs and release carbon dioxide. Ventilation is usually an involuntary process controlled by the autonomic nervous system. The levels of oxygen and carbon dioxide are kept in balance by chemoreceptors that give feedback to the central nervous and respiratory systems.

Gas exchange moves oxygen and carbon dioxide back and forth from the alveoli to the capillaries. Ventilation or air flow, and perfusion or blood flow are both necessary for gas exchange.

• Hypoxia, or a low blood oxygen level, is caused when ventilation and perfusion do not match due to alveolar dead space or shunting.
  • Dead space means the alveoli are ventilated but there is no blood flow. Emphysema is an example.
  • Shunting occurs when blood flows past the alveoli but there is no air for ventilation. Airway obstruction from pneumonia or asthma are examples.
• Children with tracheotomies breathe via the tracheostomy tube in order to get oxygen to the blood.