4 Compliance Flashcards
What do type 2 alveolar cells produce?
Surfactant, A detergent like fluid
What is the function of surfactant?
TO reduce surface tension on alveolar surface membranes. Thus reducin the chance they collapse.
What causes alveolar surface tension?
Attraction between surface molecules balances out with a net inward pull
How does surfactant affect compliance?
It increases compliance (distensibility) effectively making breathing easier
Where is surfactatn most effective?
On small alveoli because the surfactant molecules get closer & more concentrated.
Why is pressure greater in smaller alveoli?
P = (2 x surface tension)/radius
SMaller alveoli have a smaller radius & the same surface tension
When is surfactant produced?
Starts ~25 weeks
Complete by ~36 weeks
What surfactant related syndrome is often suffered by premature babies?
IRDS
Infant REspiratory Distress Syndrome
What stimulates surfactant production?
Thyroid hormones
Cortisol
Both increase towards end of pregnancy
What is compliance?
How much the lung volume changes for any given change in Ip pressure
What does high compliance mean?
The lung will have a large volume increase for a small intrapleural pressure decrease
How does compliance relate to elasticity & stretchability?
Compliance is a measure of stretchability (how easy the lung is to fill with air)
It doesnt tell you anthing about elasticity (how easily the air is pushed out)
Law of Laplace?
P = 2T/r
Tells us the inwardly directed pressure of the alveoli
What kind of alveoli collapse most easily?
Smaller alveoli because theyre inwardly directed pressure is the largest. Surfactant combats this
What hapens in IRDS?
No surfactant
Very high inward pressure in alveoli
So lots of small alveoli collapse between breaths
Makes it very hard to breath
What alveoli are most efficient?
The smaller ones because they have the largest surface area:volume ratio
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How does age affect compliance?
Compliance decreases over age