Law of Laplace and surface tension PPT

Question 1

Tension defined

Answer 1

the internal force generated by a structure

Question 2

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

Answer 2

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

Question 3

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

Answer 3

as a structure expands its radius, wall tension increases

Question 4

How is this law applied to real life?

Answer 4

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

Question 5

How does the law of LaPlace work with Spheres?

Answer 5

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

Question 6

how is LaPlaces law applied to real life in spheres

Answer 6

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

Question 7

LaPlaces law in the alveoli

Answer 7

2T=Pr
or
P=2T/r

Question 8

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

Answer 8

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

Question 9

Alveoli are unique spheres b/c why?

Answer 9

they have H20 covered membrane

and water has surface tension

Question 10

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

Answer 10

pull toward a smaller radius and collapse

Question 11

the collapse of the alveoli is driven by what?

Answer 11

surface tension of H2O

van der Wall’s forces

Question 12

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

Answer 12

Surface tension

Question 13

In the alveoli surface tension is _____ ____

Answer 13

wall tension

Question 14

Law of Laplace explains what in the Alveoli

Answer 14

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

Question 15

surfactant is composed of what?

Answer 15

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

Question 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

Answer 16

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

Question 17

T=Pr example in Normal Alveoli

Answer 17

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

Question 18

what cause the alveoli to collapse?

Answer 18

the water

without it they would stay open like a shopping bag

Question 19

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

Answer 19

0.8

Question 20

V/Q mismatch occurs with what?

Answer 20

inadequate flows

Question 21

Alveolar Gas equation relates what to what?

Answer 21

PAO2 to FiO2

Question 22

Formula for Aveolar Gas Equation

Answer 22

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)

Question 23

What is the shorcut for estimating PaO2 from FiO2

Answer 23

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

ex 0.21 x 5 = 105