
Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Respiratory physiology
Introduction
Respiratory physiology is the branch of human physiology focusing upon respiration.
Topics include:
Volumes
Volumes
Mechanics
Mechanics

Breathing in, or inhaling, is usually an active movement. The contraction of the diaphragm muscles cause a pressure variation, which is equal to the pressures caused by elastic, resistive and inertial components of the respiratory system.
<math> \begin{align} P &= P_{el} + P_{re} + P_{in} \\ P &= EV + R\dot{V} + I\ddot{V} \end{align} </math>
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.
- Anatomy: pleural cavity, thoracic diaphragm, Intercostales externi muscles, Intercostales interni muscles
- inhalation and exhalation
- lung, pulmonary alveolus
- With insufficient pulmonary surfactant, the pulmonary alveoli collapse, causing atelectasis (in infants, infant respiratory distress syndrome)
- the law of Laplace,
- compliance (physiology) – decreased with fibrosis, increased with emphysema[1]
- Poiseuille’s law
- asthma and COPD
- hysteresivity
Circulation, ventilation, and perfusion
Circulation, ventilation, and perfusion

- pulmonary circulation
- positive pressure ventilation
- hypoxic vasoconstriction
- ventilation (physiology), perfusion, ventilation/perfusion ratio (V/Q), and ventilation/perfusion scan
- shunts: right-to-left (tetralogy of fallot), left-to-right (patent ductus arteriosus)
- respiratory rate and respirometer
Gas exchange/transport (primarily oxygen and carbon dioxide)
Gas exchange/transport (primarily oxygen and carbon dioxide)

Control and response
Control and response

- control of respiration
- reticular formation
- pons (apneuistic and pneumotaxic)
- chemoreceptors (medulla, carotid body, aortic body)
- Hering-Breuer reflex
- involuntary control of respiration
- exercise
- hyperoxia
- hypoxemia (hypoxic hypoxia)
Disorders
Disorders
External links
External links
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]




