Surface Tension and alveoli

[aysenur]

how can we determine the magnitude of alveoli surface tensions according to size of alveoli, I mean I know that smaller alveoli have larger concentration of surfactant and their surface tension is small but actually we don't know the amount of surfactant in different alveoli, so how can we talk about surfactant concentration.
So actually the real question is that what determines the surface tension other than surfactant or can we know concentration of surfactant in different alveoli, is there a formula or something else?
please, help?

---

Members don't see this ad.

 

[mik30102]

how can we determine the magnitude of alveoli surface tensions according to size of alveoli, I mean I know that smaller alveoli have larger concentration of surfactant and their surface tension is small but actually we don't know the amount of surfactant in different alveoli, so how can we talk about surfactant concentration.
So actually the real question is that what determines the surface tension other than surfactant or can we know concentration of surfactant in different alveoli, is there a formula or something else?
please, help?

I'm not quite sure I understand your question? The alveolar follow the law of laplace. You can think of surface tension being static based on the fluid air interface determining it with surfactant lowering the tension due to the stabilization of the intermoelcular forces of water. Since t=pr/2 at a lower radius you need higher pressure to overcome the surface tension. Its not possible to know the exact tension within a single alveoli. You really only need to know trends, ie preemies have not yet made enough surfactant so overall they will have high tension and collapse.

 

[futuremdforme]

how can we determine the magnitude of alveoli surface tensions according to size of alveoli, I mean I know that smaller alveoli have larger concentration of surfactant and their surface tension is small but actually we don't know the amount of surfactant in different alveoli, so how can we talk about surfactant concentration.
So actually the real question is that what determines the surface tension other than surfactant or can we know concentration of surfactant in different alveoli, is there a formula or something else?
please, help?

Also confused about the question.
Premies are deficient in surfactant, so that's why their alveoli collapse.

The alveoli at the bottom of lungs get smaller on expiration from gravity of the rest of the body pushing down. They expand a lot during inspiration. The alveoli at the apex are larger on expiration, but they don't get much bigger on inspiration. The alveoli at the bottom are at the biggest risk of collapse in people with breathing problems, like fibrosis (low compliance). That's why you will hear crackles - it's these alveoli popping open. You can picture a balloon - you know how there is a critical point where it's easier to inflate the balloon? It's the same for alveoli.

 

[zero0]

Can't say I know what you're going for either, but since I'm on the respiratory block myself, I'll chime in.

I don't know if you can say that the concentration of surfactant increases upon expiration, since it stays on the alveolar wall and the volume of water on the alveolar walls normally doesn't change. The surfactant molecules do get more crowded/compressed on expiration however which limits water's ability to hydrogen bond and reduces surface tension.

I wouldn't worry about calculating surfactant concentrations, nor can I say for sure if there's any clinically relevant way of doing this. Just know that surfactant reduces the surface tension of the water droplets lining the inside of the alveoli. It prevents alveoli from collapsing completely under the force of surface tension and also allows lungs to expand more easily. It also plays a role toward the end of inspiration in limiting lung expansion. As the surfactant molecules become more spread apart, this allows water to interact more with itself and creates surface tension.


Then there's the clinical significance of infant respiratory distress syndrome. No surfactant means alveoli collapse completely.

 

[JamaicanHerb]

via Imgflip Meme Generator

 

[aysenur]

Let' say a is a small alveolus and b is a large alveolus. According to Laplace law 2Ta/r=Pa 2Tb/2r=Pb. on account of the small alveolus not to be collapsed the Pa has to be equal to Pb and Tb=2Ta. after that point I confused and thought about surfactant because the only thing I knew changing the tension is surfactant. But change in surfactant concentration has to be proportional with surface area this means proportional with r3.According to that Tb can't be 2 times Ta
So I've tried to ask this