Lecture 18 - Mechanics of breathing Flashcards
What is respiration?
The exchange of gases between atmosphere blood and cells
What are the three steps of respiration?
Pulmonary ventilation
External respiration
Internal respiration
What is pulmonary ventiliation?
Inspiration and expiration of air between atmosphere and lungs
Physical movement of air
What are the two principles required for pulmonary ventilation?
Boyles law
Air flows from high to low pressure
What is Boyles law?
When the temperature of a gas is constant, the pressure changes inversely with the volume
IE they switch
What is external respiration?
Exchange of gas between alveoli and blood in pulmonary capillaries
Blood gains oxygen and loses carbon dioxide
What is internal respiration?
Exchange of gas between blood in capillaries and tissue cells
What are the two forces that cause resistance to breathing?
Lung compliance
Airway resistance
What is lung compliance?
How easy it is for the lungs to expand
What are the three factors that can effect lung compliance?
Elasticity of lung tissue
Surface tension of alveoli
Mobility of chest wall
What is meant by the elasticity of lung tissue?
The measure of the elastic recoil of the lungs
A measure of the changes in lung volume resulting from a given change in pressure
Formula:
Compliance = change in volume/change in pressure
What is meant by the surface tension of alveoli?
It is caused by intermolecular forces between molecules in a liquid
Air-fluid interface surface is under tension like a thin membrane being stretchedW
What is Laplace’s law?
The relationship between pressure, surface tension and the radius of an alveoli bubble
Formula:
P = 2T/r
What is surfactant and what is it for?
Helps keep alveoli in uniform size
Reduces the work needed to expand alveoli with each breath
What is neonatal respiratory distress syndrome?
A condition where there is a lack of surfactant secretion in premature babies
There is reduced compliance and alveoli can collapse on exhalation
