This document gives you the description about mechanics of breathing and pressure changes associated with it . Students find it difficult to grasp concepts related to pressure differences occurring in lungs so here is a well explained series consisting of three parts on Lungs and breathing mec...
Respiratory | Mechanics of Breathing:
Pressure Changes | Part 1
Ninja Nerd
The mechanics of breathing is going to be a tough topic for certain
people to understand, especially with the pressures, so we 're going
to do our best here and engineered science to make sense of that.
So it 's going to dig right in so before we do that we need to look at
a little bit of anatomy for the lungs. there's three main pressures
that we 're going to talk about let 's denote these pressures. A B and
c. pressure is actually referred to as the intrapulmonary pressure, so
it's referred to the intra pulmonary or intra-alveolar pressure..
pressure can reduce what's called pleurisy due to not enough
pleural fluid being produced. we 're going to give you numbers for
each one of these pressures. I got ta explain a little relationship
between the two okay so I 'm going to write these down here. So the
entry of pulmonary pressure is approximately approximately
approximately.. The intrapleural pressure is about 760 millimeters of
mercury.. The last one which is the c pressure is the atmospheric
pressure or the barometric pressure..
I 'm actually subtracting 760 from 760 at zero, but if I subtract 756
760, what is that that's negative 4 millimeters of mercury. what is
760 760, it 's zero so this is called this is actually technically. We can
also write that this pressure here. This intrapulmonary pressure is
also zero millimeter of mercury right and that 's because so
sometimes just so you know these can be interchangeable. the lung
is trying to pull this visceral pleura away from the parietal pleura
and the surface tension. the lungs are trying to collapse the lungs
and increase this this volume here. the chest wall when you're
breathing. What is it trying to do it's trying to push the chest wall
out to expand. Boyle 's law states that whenever there is a increase
in the pressure, there will be a direct decrease in the volume. the
dynamic interplay. Between surface tension and the elasticity of the
chest will play a role in maintaining negative intrapleural pressure..
surface tension wants to collapse alveoli, which tries to collapse the
lungs, pushing this way creating a bigger volume of potential
volume space..
There 's three pressures in the lung or basically across this whole
lung structure here right intrapulmonary pressure, which is also
, called the intra-alveolar pressure right and again we showed it by
this alveoli. There it 's approximately 760 millimeters of mercury.
Then we said that there 's a pressure here which is the intrapleural
pressure. the elasticity of the lungs in the surface tension they want
the lungs to collapse.. Boyle 's law says that whenever the volume is
increasing the pressure in this actual cavity is decreasing. the
dynamic interplay between the elasticity the lungs and the surface
tension and the. elasticity of the chest wall helps to keep this
volume increasing. outwards, but whenever we 're resting it wants
to kind of actually just maintain that size, but it can have a force
that. is Is kind of trying to direct inwards a little bit right, but no
matter what. I 'll be able to pressure and travel pressure. I'm just to
noting in here so it 's close to this. This is the B pressure, which was
the intrapleural pressure and here was the seed pressure. we 're not
going to spend a lot of time, but I want you to understand that there
is other pressures a pressure across a wall. So for example,
remember we said that this was intrapulmonary pressure. Let's
denote it again with a B. This is a right here..
Trans respiratory pressure I 'll write it up here trans respiratory
pressure and with this transthoracic pressure and trans-pulmonary
pressure. What is the significance of this okay well. Let's write out a
little formula here So let me actually bring this one down a little bit
so we have more room. I 'm going to bring it down here.
transthoracic pressure is equal to the anti B intrapleural pressure.
So I'm going to put P IP minus B atmospheric pressure, which is the
pressure C so P of the atmosphere. negative formula Musa Mercury
means that is trying to deflate that 's why the chestwall is deflated.
positive pressure means that you 're trying to inflate the structure
now if we look at transthoracic pressure what 's happening here.
This one 's a little interesting right because you're taking the
intrapleural pressure subtracting from the atmospheric pressure..
Respiratory | Mechanics of Breathing:
Inspiration | Part 2
Ninja Nerd
So, to increase the volume of the thoracic cavity, we have the
external intercostals contracting and pulling the ribs outward. This
action increases the space within the thoracic cavity, which can lead
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