Law of Laplace and surface tension PPT Flashcards Preview

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Flashcards in Law of Laplace and surface tension PPT Deck (23):
1

Tension defined

the internal force generated by a structure

2

Law of laPlace states that for cylindrically shaped structures the formula is what?

T=Pr
T=wall tension
P= pressure of liquid in cylinder
r= radius

3

what does the law of LaPlace show or mean ( a lose definition)

as a structure expands its radius, wall tension increases

4

How is this law applied to real life?

Aortic aneurysms is more likely to rupture than a normal segment of the aorta b/c the radius is greater = increased wall tension

also capillary will withstand a pressure of 100mmHg better than a vein b/c capillary has a tiny radius compared to a vein

5

How does the law of LaPlace work with Spheres?

The ratio is doubled
2T=Pr
or (T= Pr/2)

6

how is LaPlaces law applied to real life in spheres

the LV, the greater the filling pressure, the greater the tension in the ventricular wall.

7

LaPlaces law in the alveoli

2T=Pr
or
P=2T/r

8

Laplaces law in the alveoli states that pressure needed to expand an alveolus is diresctly proprtional to__1__ and inversly proportional to __2__

1) surface tension
2) radius
P=2T/r

9

Alveoli are unique spheres b/c why?

they have H20 covered membrane
and water has surface tension

10

Alveoli act like bubbles and bubbles tend to pull toward what? and do what?

pull toward a smaller radius and collapse

11

the collapse of the alveoli is driven by what?

surface tension of H2O
(van der Wall's forces)

12

what is the cumulative effects of cohesive intermolecular forces on the surface of a fluid at a liquid/gas or liquid/liquid interface

Surface tension

13

In the alveoli surface tension is _____ ____

wall tension

14

Law of Laplace explains what in the Alveoli

what would happen in the alveoli if not for surfactant
-smaller alveoli would empty into larger alveoli
-smaller alveolar spheres would be more difficult to expand than large alveoli

15

surfactant is composed of what?

dipalmityl phosphatidylcholine and Phospholipids (lecithin and spingomyelin) secreted by the alveolar (type II) cells

16

We all know that small alveoli are not harder to inflate compared to large alveoli. If this was true we wouldn't have such well matched ventilation and perfusion ratios. thus we know that sufactant lowers __1__. and that small alveoli have more concentrated __2__ vs expanded (larger) alveoli and thus are easier to expand. so __3___ radius ___4___ surface tension by ___5___ surfactant concentrations

1) surface tension
2) surfactant
3)decreaseing
4) decreases
5) increasing

17

T=Pr example in Normal Alveoli

if r decreases, T decreases with P constant
-pressure in alveoli doesn't change
-surfactant is the great equalizer
- explainds why small alveoli don't empty into large alveoli in normal lungs

18

what cause the alveoli to collapse?

the water
(without it they would stay open like a shopping bag)

19

With adequate alveolar gas flow normal ventilatory to perfusion ration of _____ should be maintained

0.8

20

V/Q mismatch occurs with what?

inadequate flows

21

Alveolar Gas equation relates what to what?

PAO2 to FiO2

22

Formula for Aveolar Gas Equation

PAO2 = Fio2 x (Patm - PH2O) - PaCO2 / RQ
PAO2= alveolar oxygen tension
FiO2= inspired O2 concentration
Patm= 760 mmHg
PH20= 47 mmHg @ body temp
PCO2= 25-45 mmHg
RQ= respiratory quotient (normal 0.8)

23

What is the shorcut for estimating PaO2 from FiO2

FiO2 < 50% multiply FiO2 by 5
FiO2 > 50% multiply FiO2 by 6
the product is calculated PaO2

ex 0.21 x 5 = 105