Respiratory System Flashcards
What causes lung surface tension?
The air-liquid interface formed by the thin layer of fluid lining the internal surface of the alveoli. While quite elastic, the lung is quite compliant too.
What is the formula for Lung compliance?
Lung Compliance = ^V/^(Palv - Pip)
What are the two factors contributing to elasticity?
Elastin fibers in alveolar wall.
Alveolar surface tension–bigger contributor.
What causes surface tension in general?
Water having a greater attraction for itself than air.
What happens when water line the inside of an air filled sphere (alveolus)?
Surface tension tends to collapse the sphere. The smaller the sphere, the greater the tension.
What is the formula collapsing pressure due to surface tension? and variables?
P = 2T/r
P – collapsing pressure
T – surface tension
r – radius of the sphere.
What is the relationship of work and surface tension?
The surface tension of a liquid is a measure of the work required to increase the surface area of the liquid by a certain amount.
What is surfactant?
Detergent-like substance (lipids with no surface tension) mixes with H2O to reduce surface tension in alveoli.
What happens if a lung does not have surfactant?
smaller alveoli will suffer collapsing pressure that pushes air to larger alveoli. This would cause a chain reaction until there was, effectively, one giant alveoli. `
What does lung quality does surfactant increase?
Increases lung compliance and decreases the work of breathing.
What happens if lung compliance decreases? Give two examples of how it happens.
The respiratory muscles must do more work to expand the lungs to a given volume.
Scar tissue from tuberculosis–thickens lung tissue
Infant respiratory distress syndrome–reduces surfactant.
From a physics perspective, how does surfactant maintain pressure in the lungs?
In order to equalize surface tension, surfactant is distributed in greater concentrations across small alveoli than large alveoli. In this way, surfactant maintains stable volume and pressure across the lung.
What causes airway resistance?
What is its formula?
Airflow formula?
Changes in ventilatory system resistance are all due to changes in conduction vessel radius since air viscosity and vessel length virtually never change.
R = Ln8/r4pi
Air flow = (Patm - Palv) pi* r4/Ln8
How do the lungs respond to an increase in alveolar pressure (any increase in resistance to inspire)? (Palv)
The pressure to overcome the resistance is directly proportional to the amount of added resistance.
What is the difference in alveolar and atmospheric pressure in passive breathing?
2 mmHg.
