the

Overview of The Pleural Cavity

you guys we are talking about the

pulmonology physiology and this is the

pneumothorax so we are not doing the

treatment of the pneumothorax it's not

step two lecture what we are doing is

we're doing pneumothorax and the

mechanism of the new pneumothorax so

let's look at it quickly here is what

happens in the normal chest so let's say

if I make two lungs here and we make

trachea and the bronchi we know that the

lungs are covered how do we know that we

just did that in our other lectures that

lungs are covered with two type of flora

one is the visceral pleura that is what

I'm drawing in this green this visceral

pleura is stuck it is stuck to thee to

the lungs

it is almost part of the the lungs

external surface and then is the

parietal pleura that is not connected

with the lungs instead lungs are sort of

floating in it freely and the frighted

pleura all right laura is then connected

with the chest wall so this is the ribs

these are the ribs right and the ribs

are connected with the parietal pleura

the whole chest wall is connected with

the parietal pleura and that chest wall

keeps the parietal pleura moved you know

pulled outwards so the the cavity

between the visceral and parietal pleura

is the pleural cavity

so today's story today's problem today's

topic is about this cavity so normally

what happens is the pleural cavity it

has a small suction effect because of

the lymphatics I always make that as a

small faucet like structure so this is

the parietal pleura cavity pleural

cavity has normally a pressure of minus

5 centimeter of water right so that is a

normal situation now lungs are pulled

out because of this minus centimeter so

what happens is chest cavity pulls the

parietal pleura out parietal pleura

exerts pressure on the fluid in this

here and tries to suck the fluid

outwards fluid is then causing a suction

effect on the visceral pleura visceral

pleura is tightly bound to the lungs so

the lungs are pulled out that is how the

outward pull happens and that is why

there is - 70 - 5 centimeter of water

pressure now imagine this for a second

before we talk about pneumothorax

imagine this for a second if this

suction effect is taken away if this

outward pull is taken away then the

lungs have a tendency to collapse right

we did that in our previous lectures

what contributes to that tendency to

collapse we know that there is the fluid

air interface problem or surface tension

generated by that and secondly there is

the surface tension generated by elastin

and collagen fibers that are trying to

that are trying to recoil so if you

somehow remove the forces out here that

are pulling the lungs open then the

forces that are moving that are pulling

the lungs inwards recoil forces will win

in the lungs which shrink and collapse

so this is the

recoil forces recoil forces we've talked

about it one third is the tissue elastin

and fibrin 2/3 1/3 of the forces are

thee the fluid present in alveoli fluid

in alveoli alveoli we have liked this

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