Respiratory physiology

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Gaseous exchange in the lung.

Respiratory physiology is the branch of human physiology focusing upon respiration.

Topics include:



Front view of thorax.

Inhalation (breathing in) is usually an active movement. The contraction of the diaphragm muscles causes the thoracic cavity to increase in volume, thus decreasing the pressures within the lung (Intrapleural and Alveolar Pressures). This negative pressure within the lungs acts as a Pressure Gradient, thus pulling air into the lungs. As air fills the lungs, the negative alveolar pressure moves back towards atmospheric pressure, and air flow into the lungs slows down. In contrast, expiration (breathing out) is usually a passive process.

P &= P_{el} + P_{re} + P_{in} \\
P &= EV + R\dot{V} + I\ddot{V} 

Where Pel equals the product of elastance E (inverse of compliance) and volume of the system V, Pre equals the product of flow resistance R and time derivate of volume V (which is equivalent to the flow), Pin equals the product of inertance I and second time derivate of V. R and I are sometimes referred to as Rohrer's constants.

Circulation, ventilation, and perfusion[edit]

Pulmonary circulation

Gas exchange/transport (primarily oxygen and carbon dioxide)[edit]

Oxygen-hemoglobin dissociation curve

Control and response[edit]



See also[edit]

Additional images[edit]


  1. ^ Compliance

External links[edit]