lecture 17 - the work of breathing Flashcards
What determines the direction of airflow into/out of the lungs?
The difference between atmospheric and intrapulmonary pressure
What is the pressure inside the lungs?
Intrapulmonary pressure
What is the pressure outside the lungs?
Atmospheric pressure
What are the 2 opposing forces that must be overcome to take a breath?
Stiffness of the lungs, resistance of the airways to the lungs due to friction
What is compliance, in terms of the lungs?
The magnitude of the change in lung volume produced by the given change in pressure - how ‘stiff’ the lungs are
What is the equation for lung compliance?
C= ΔV/ΔP
What distinct condition is characterised by low compliance/ ‘stiff lungs’?
Pulmonary fibrosis
What are the characteristics of pulmonary fibrosis?
Thickening and scarring of alveolar membranes due to chronic inflammation or exposure to industrial chemicals, resulting in decreased lung compliance
What is the cause of surface tension in the lungs?
Fluids surrounding the lungs exert surface tension
What is surface tension?
The tendency of a fluid surface to occupy the smallest possible surface area.
Why does surface tension arise?
Due to hydrogen bonds
What is the cause of surface tension in the alveoli?
They are lined with fluid and have very thin walls which enhances the effects of surface tension
How does surface tension affect lung function?
Causes stiffness that must be overcome to expand the lungs
how does surfactant reduce lung stiffness?
By reducing surface tension in the alveoli and makes them easier to expand.
How does surfactant lower the surface tension in the fluid in alveoli?
Reduces the attractive forces between fluid molecules by inserting hydrophobic ligands between H2O molecules
