Respiratory | Mechanics of Breathing: Inspiration | Part 2

Summary

This educational video script delves into the mechanics of breathing, focusing on the inspiratory process. It outlines the role of the central nervous system, the diaphragm, and external intercostal muscles in expanding the thoracic cavity. The script explains how these actions decrease intrapleural and intrapulmonary pressures, creating a pressure gradient that facilitates air flow into the lungs. The video uses analogies and models to illustrate these concepts, aiming to provide a clear understanding of the respiratory process.

Takeaways

• 🧠 The process of breathing is controlled by the central nervous system, including the midbrain, pons, medulla, and spinal cord.
• 💪 Key muscles involved in the inspiratory process are the external intercostals and the diaphragm, which are innervated by the phrenic nerve and intercostal nerves, respectively.
• 📉 During inhalation, the contraction of the external intercostals and diaphragm increases the thoracic cavity volume, leading to a decrease in intrapleural and intrapulmonary pressures.
• 🔁 The ventral respiratory group in the medulla also plays a role in stimulating the nerves that control the external intercostals and diaphragm.
• 📌 The external intercostals pull the ribs outward and upward like a bucket handle, while the diaphragm contracts and moves downward, collectively increasing the thoracic cavity volume.
• 🌀 According to Boyle's Law, as the volume of the thoracic cavity increases, the intrapleural pressure decreases, creating a pressure gradient that allows air to flow into the lungs.
• 🌐 The atmospheric pressure remains constant during the breathing process, unaffected by the changes in thoracic cavity volume.
• 🔄 The transpulmonary pressure, which is the difference between intrapulmonary and intrapleural pressures, increases slightly during inhalation.
• 🛑 At the peak of inspiration, the intrapulmonary pressure equals the atmospheric pressure, stopping the flow of air into the lungs until the pressure gradient changes during exhalation.
• 🔮 The entire process of inhalation is a coordinated effort of the nervous system and respiratory muscles to create pressure gradients that facilitate the flow of air into the lungs.

Q & A

What is the role of the external intercostal muscles in the breathing process?

The external intercostal muscles play a crucial role in the inspiratory process by contracting and pulling the ribs outward, which increases the thoracic cavity volume. This action is often referred to as the 'bucket handle' movement.

What is the primary muscle responsible for the inspiratory process?

The diaphragm is the primary muscle responsible for the inspiratory process. When it contracts, it moves downward, increasing the volume of the thoracic cavity and facilitating the inhalation of air.

How does the contraction of the diaphragm affect the thoracic cavity volume?

When the diaphragm contracts, it domes downward, which increases the volume of the thoracic cavity. This movement is essential for drawing air into the lungs during inhalation.

What is the function of the phrenic nerve in the breathing process?

The phrenic nerve originates from the C3, C4, and C5 nerve roots and innervates the diaphragm. Its stimulation causes the diaphragm to contract, contributing to the increase in thoracic cavity volume during inhalation.

What is the significance of the intercostal nerves in the breathing process?

The intercostal nerves, which run from T1 to T11, innervate the external intercostal muscles. Their stimulation leads to the contraction of these muscles, further increasing the thoracic cavity volume and aiding in inhalation.

How does the ventral respiratory group in the medulla contribute to the breathing process?

The ventral respiratory group in the medulla contains nuclei that send axons to stimulate the neurons controlling the external intercostal muscles and the diaphragm, thereby contributing to the automatic regulation of breathing.

What is the relationship between the thoracic cavity volume and the intrapleural pressure during inhalation?

During inhalation, as the thoracic cavity volume increases due to the contraction of the external intercostal muscles and the diaphragm, the intrapleural pressure decreases according to Boyle's law.

What is the initial intrapleural pressure at rest, and how does it change during inhalation?

The initial intrapleural pressure at rest is approximately 4 mm Hg. During inhalation, it decreases to about -6 mm Hg due to the expansion of the thoracic cavity.

What is the initial intrapulmonary pressure at rest, and how does it change during inhalation?

The initial intrapulmonary pressure at rest is approximately 0 mm Hg. During inhalation, it decreases to about -1 mm Hg as the volume inside the lungs increases.

How does the transpulmonary pressure change during inhalation?

The transpulmonary pressure, which is the difference between the intrapulmonary and intrapleural pressures, increases slightly during inhalation due to the decrease in intrapulmonary pressure relative to the intrapleural pressure.

What is the trans respiratory pressure, and how does it indicate the direction of air flow during inhalation?

The trans respiratory pressure is the difference between the intrapulmonary pressure and the atmospheric pressure. During inhalation, it is negative (-1 mm Hg), indicating that air flows from the atmosphere into the alveoli.

Outlines

00:00

🧠 Central Nervous System and Breathing Mechanisms

The paragraph introduces the second part of a video series on the mechanics of breathing, focusing on how the inspiratory process affects pressure changes. It begins with an overview of the central nervous system, highlighting the midbrain, pons, medulla, and spinal cord. The discussion then shifts to the muscles involved in breathing, particularly the external intercostals and the diaphragm. These muscles are controlled by signals from the cerebral cortex through the spinal cord, specifically the phrenic nerve from C3, C4, C5, and intercostal nerves from T1 to T11. The video aims to explain how these nerves and muscles work together to initiate the process of inhalation.

05:01

💪 The Role of Intercostal Muscles in Breathing

This section delves into the function of the intercostal nerves and how they interact with the external intercostal muscles during inhalation. When these nerves stimulate the muscles, they cause the ribs to move outward, creating a bucket handle effect, and the sternum to push outward and upward, increasing the thoracic cavity volume. The video uses an anatomical model to visually demonstrate these actions and explains how these movements lead to an increase in the volume of the thoracic cavity, which is crucial for the breathing process.

10:03

📉 Pressure Changes During Inspiration

The paragraph explains the impact of the increased thoracic cavity volume on pressures within the respiratory system. As the volume increases due to the contraction of the external intercostals and the diaphragm, the intrapleural pressure decreases according to Boyle's law. The video details how the pressure changes from approximately 4 mm Hg at rest to about -6 mm Hg during inspiration. It also discusses the corresponding decrease in intra-pulmonary pressure from 0 mm Hg at rest to approximately -1 or -2 mm Hg, indicating that air will flow into the lungs due to these pressure gradients.

15:06

🔄 Transpulmonary and Transthoracic Pressures in Breathing

This section further explores the effects of increased thoracic cavity volume on transpulmonary and transthoracic pressures. The transpulmonary pressure, which is the difference between intra-alveolar and intrapleural pressures, becomes more positive during inhalation. Meanwhile, the transthoracic pressure, which is the difference between intrapleural and atmospheric pressures, becomes more negative, indicating that the chest wall is expanding outward. The video concludes by emphasizing that these pressure changes are essential for drawing air into the lungs during inspiration.

20:06

🔁 From Inspiration toExpiration: Pressure Equilibrium

The final paragraph summarizes the pressure changes that occur during the inspiratory process and sets the stage for the next video, which will cover expiration. It reiterates that the pressure gradients cause air to flow from the atmosphere into the alveoli until the intra-alveolar pressure equals the atmospheric pressure. The video stresses the importance of understanding these mechanics for a complete grasp of the breathing process and hints at the reversal of these events during exhalation.

Keywords

💡Inspiratory Process

The inspiratory process refers to the series of physiological actions that occur to draw air into the lungs. In the video, this process is described as starting with the contraction of muscles such as the diaphragm and external intercostals, which increase the thoracic cavity volume. This is a fundamental concept in the video, as it sets the stage for explaining how breathing mechanics lead to changes in pressures within the respiratory system.

💡Central Nervous System

The central nervous system (CNS) is composed of the brain and spinal cord and plays a crucial role in the control of breathing. The script mentions the midbrain, pons, medulla, and spinal cord as parts of the CNS involved in the regulation of breathing. The CNS sends signals to initiate the inspiratory process, illustrating the video's theme of how the nervous system controls respiratory mechanics.

💡External Intercostals

The external intercostals are muscles located between the ribs that play a significant role in the inspiratory process. As explained in the video, when these muscles contract, they pull the ribs outward, increasing the thoracic cavity volume. This action is essential for understanding how the mechanics of breathing lead to the necessary changes in pressure to facilitate inhalation.

💡Diaphragm

The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The video script describes the diaphragm as a 'big beast' that contracts during inhalation, moving downward and increasing the volume of the thoracic cavity. This action is critical for the understanding of the video's main theme, as it directly impacts the pressure changes necessary for breathing.

💡Cervical Plexus (C3, C4, C5)

The cervical plexus, particularly the nerves from C3, C4, and C5, is mentioned in the script as being responsible for innervating the diaphragm. These nerves are part of the phrenic nerve, which, when stimulated, causes the diaphragm to contract. This is a key concept in the video, as it links the nervous system's control to the actual muscle movements involved in breathing.

💡Intercostal Nerves

Intercostal nerves, running from T1 to T11 as described in the video, are responsible for innervating the external intercostal muscles. These nerves play a crucial role in the inspiratory process by sending signals that lead to the contraction of the external intercostals, thereby increasing the thoracic cavity volume. The intercostal nerves are a vital component of the video's discussion on the mechanics of breathing.

💡Ventral Respiratory Group

The ventral respiratory group is a set of nuclei located in the medulla oblongata, which is part of the brainstem. As explained in the video, these nuclei have connections that can stimulate the neurons supplying the external intercostals and the diaphragm. This concept is important for understanding the automatic, involuntary control of breathing, which is a key theme in the video.

💡Thoracic Cavity Volume

The thoracic cavity volume is a critical concept in the video, as it directly relates to the mechanics of breathing. The script describes how the contraction of the external intercostals and the diaphragm increases this volume, which in turn affects the pressure within the respiratory system. Understanding the changes in thoracic cavity volume is essential for grasping the video's explanation of how inhalation occurs.

💡Intrapleural Pressure

Intrapleural pressure, also known as intraplural pressure, refers to the pressure between the two layers of the pleura surrounding the lungs. The video explains how the increase in thoracic cavity volume leads to a decrease in intrapleural pressure, which is a key concept in understanding the pressure gradients that facilitate inhalation.

💡Transpulmonary Pressure

Transpulmonary pressure is the difference in pressure between the inside of the lungs (intrapulmonary pressure) and the outside (intrapleural pressure). The video script uses this concept to explain how the pressure changes during inhalation, which is crucial for understanding the video's overall message about the mechanics of breathing.

Highlights

Explanation of the inspiratory process and its effect on pressures within the respiratory system.

Role of the central nervous system, particularly the midbrain, pons, medulla, and spinal cord, in initiating the breathing process.

Importance of the external intercostal muscles in the inspiratory process.

The diaphragm's crucial role as a muscle in the breathing process, separating the thoracic cavity from the abdominal cavity.

Voluntary control over skeletal muscles like the diaphragm and external intercostals via signals from the cerebral cortex.

Description of the phrenic nerve, which arises from C3, C4, and C5 nerve roots and innervates the diaphragm.

Functioning of the intercostal nerves from T1 to T11, which stimulate the external intercostal muscles.

The ventral respiratory group in the medulla and its connection to the nerves supplying the external intercostals and diaphragm.

Mechanism by which the external intercostal muscles contract to increase the thoracic cavity volume.

Visual demonstration of the bucket handle movement of the ribs and the pump handle action of the sternum during inspiration.

The diaphragm's action of doming down and its contribution to increasing the thoracic cavity volume.

Decrease in intrapleural pressure during inspiration due to the expansion of the thoracic cavity.

Correlation between increased thoracic cavity volume and decreased intra-alveolar pressure.

Explanation of how the atmospheric pressure remains constant during the breathing process.

Changes in transpulmonary, transthoracic, and transrespiratory pressures during inspiration.

Final equilibrium of intrapulmonary pressure with atmospheric pressure at the peak of inspiration.

Anticipation of the next video, which will cover the mechanics of expiration.

Transcripts

all right ners so if you guys here for

Part Two for the mechanics of breathing

appreciate it what we're going to do now

is we're going to go over exactly how

this actual inspiratory process can

produce these changes in these pressures

okay so let's go ahead and get started

so where does this all start okay let's

say that we have here our actual central

nervous system all right so we have

again the midbrain the ponds the medulla

right so we we'll quickly outline that

again we're going to have the midbrain

here all right

midbrain you'll have the

pawns you'll have the medulla right here

and then you'll even have right here

which is our spinal

cord so we're taking a um an actual

sagittal section here so I'm taking A

sagittal section we're looking at like

that so in other words I'm taking here

and I'm cutting right down all right now

whenever we want to breathe since this

muscle here you see how we have the ribs

we took a cross-section of the ribs here

connecting between the ribs you see

these muscles right here these red

muscles right there these ones right

here are specifically

called the

external intercostals so they're called

the external

intercostals now the external

intercostals are kind of really

important muscles for this entire

inspiratory process okay they're one of

the big ones but an even really really

more important one is this big beast

right here you see this big guy right

here all the way from one end to the

other this big muscle right here is a

very important muscle this big old Beast

right here is called the diaphragm okay

so this is called the

diaphragm so you have two really

important muscles here external

intercrosses which are in between the

ribs and the diaphragm right which is

going to be right here right underneath

it's actually what separates the nice

thoracic cavity from the abdominal

cavity okay now

whenever we want to be able to contract

these since these are skeletal muscles

we have voluntary control over our

skeletal muscles so let's say from the

cerebral cortex right from the cerebral

cortex we'll have it coming down from

here you can't see it but it's coming

down from here right you could have

signals coming down here you could have

signals coming down here and actually

stimulating some specific uh nerves

within the spinal cord right so let's

say for example if this is uh going to

be

C3 C4 and C5 this would come out

activate these sematic motor neurons and

come and

inate the diaphragm okay so this would

be C3 C4 C5 nerve rout this is going to

be specifically called the frenic nerve

they actually call this the frenic

nerve

okay whereas you have another structure

let me get Skelly out of the way here

you have another structure here let's do

this one one

in let's actually do this one in this

nice color here let's say that we keep

coming down here though and we come down

to

about you know we're not going to draw

all of them but there's a couple other

ones down in the thoracic region we'll

just do a couple of them and we'll say

for right here we have from T1 all the

way down to about t11 so all the way

down we're not drawing all of them but

for the sake of it I drew a couple here

from T1 all the way down to about t11

you have these intercostal nerves here

and These Guys these intercostal nerves

are actually going to come and innervate

we actually have them coming through

here they're going to be inating the

external

intercostals and when they inate the

external intercostals they're going to

provide a stimulus to the external

intercostals so so far what do we have

here I'll put it like here so it looks

good let's do this like that yeah all

right so we got the frenic nerve coming

here from the C3 C4 C5 nerve rootes

interva in the diaphragm then we have

from T1 all the way down to t11 we're

going to have this intercostal nerves

right so you're going to have your

inter

costal nerves and this could be

activated by cortical control right so

we have cortical control there but you

know what else can actually stimulate

these also we're going to talk about it

in more detail but you have a specific

set of nuclei located here within the

medulla a spe a special set of nuclei

these nuclei are actually called the

ventral respiratory group and the

ventral respiratory group actually has

connections okay that can actually run

here and

provide these axons that can stimulate

these actual neurons that are going out

to supply the external intercostals as

well as the diaphragm so you have input

coming from the cerebral cortex as well

as even from What's called the vental

respiratory group within the medulla

anyway when these guys are coming out

from the frenic nerve and the internal

inter internal intercostal nerves what's

happening let's first look at how the

actual intercostal nerves are working so

we're work from top to bottom so the

intercostal nerves come over here to the

external intercostal and they cause them

to contract now when the actual external

intercostal muscles contract something

really really cool happens I'm going to

show you personally but then I'm going

to bring in an actual Anatomy model so

we can see it in a better way so what

the external intercostals do is when

they contract they pull the ribs outward

so they pull the ribs like they're

coming out so you know whenever you have

like a a bucket with the two handles so

if you have like a bucket with the two

handles and you pull the handles

actually like this that's exactly what's

happening to the ribs so one thing

that's happening is you're taking the

ribs and pulling them outward which is

increasing the thoracic cavity volume so

as you pull the ribs outward that

increases the thoracic cavity volume

another thing whenever the actual

external neosales contract they pull the

sternum they push the sternum out like

this okay so when they push the sternum

out out and upward like this that

increases the thoracic cavity volume

anteriorly a little bit anterior

posterior whereas whenever the uh ribs

go outward that increases it in a

horizontal volume right either way

nonetheless when the extr cost is

contract they pull up they call it like

a bucket handle movement and then

whenever the actual external Coss is

contract they pull the sternum outward

which is kind of like if you guys ever

seen like the water F like the the old

school ones that you do like the pump

action there that's what they call they

call it like the little water pump

action which is actually pull the

sternum out either way the whole result

is increasing the thoracic cavity volume

okay so I want to give you guys a better

example now so what I'm going to do is

I'm going to bring in the an actual

skeleton model here so we can get a

better idea of what this looks like here

because I want to I want to make sure

that this is really really

understandable here so again here we're

going to have all of these structures

these are our ribs okay so all of these

are the ribs okay the external Cal is

actually attach between the ribs so

let's pretend this is actually a rib

here a rib here the external inter Cal

would attach here now what they do is

the lower part of the rib where the

external intercostal is attaches to it

pulls that rib up so when it pulls the

ribs up what look what it actually would

do it would pull the ribs out like this

so you're actually going to pull them

outward like this okay so whenever

they're Contracting when the external

inter cost is contract they pull the

ribs outward like this now and also what

they do is whenever they're Contracting

they kind of push the sternum outward so

two things are happening the ribs are

going outward and the volume in here is

actually increasing also the sternum is

is coming out farther and the volume in

here is increasing so that should make

sense now okay now let me grab another

model real quickly so we can even see a

little bit better about these actual

muscles here so let me bring this back

in here so if we see here we got the

Skelly now what I'm going to do is I'm

going to take this actual chest plate

here put in front of it okay so if you

guys look here for a second you're going

to notice again here's our ribs but you

see these muscles right here on the edge

these muscles right there are your

external intercostals when they contract

so let's imagine we look at this

external intercostal this point here is

actually going to pull that actual rib

up so this is the insertion this point

here is actually fixed that's the origin

so when it contracts it pulls the

insertion up towards the origin when it

does that again sternum goes out which

increases the thoracic cavity volume and

the ribs come out like a bucket handle

which is increasing thoracic cavity

volume okay so now I'll put these guys

back and we'll get back to our actual

tutorial

here okay so now that we've done that we

should have a good idea what's happening

now so let's actually show that now in a

better way here in this diagram now okay

so that's the first thing that happened

so the thoracic cavity volume is going

to increase so let's say that that

happened the thoracic cavity volume over

here let's say that it actually

increased so it went out wider okay so

if that's the case we would expect the

volume in the thoracic cavity to start

increasing before we do this actually

before I do this let me do one more

muscle so we can get one more muscle in

here last one is the diaphragm okay what

does the diaphragm do we really need to

think about him too right before we go

over there and show that so the

diaphragm when he

contracts what actually happens is he

actually domes down so he actually

depresses if he depresses think about

this for a second let me actually show

you what would look like over here if

this muscle contracts let's say that

it's actual muscle

contracted look at what happened to all

of this volume here look at this let's

say that it actually went down a little

bit oh wow that's a lot of volume there

so if that sucker went down what's going

to happen to this area now what happens

to this volume so now the volume is

increasing by three ways one is the diap

frame is actually depressing increasing

thoracic cavity volume the second one is

the external NE costal are pulling the

ribs upward right and outward which is

pulling them like a bucket handle and

pulling the sternum outward all of those

things are doing what what's the overall

result increasing thoracic cavity volume

let's write that down so what's the

first thing that

happened external

intercostals and diaphragm

contract and whenever these suckers

contract what

happens by the mechanisms that we

mentioned many times already it

increases the

thoracic cavity

volume okay cool well now let's see how

this affects these many

pressures if I can increase the thoracic

cavity volume let's think for a second

what can happen because technically this

is all connected to the chest wall right

as the chest wall is expanding and as

this is going down what we would expect

to happen here with this whole parietal

plural wouldn't we expect it to actually

expand a little bit also and to actually

go with the actual chest wall so let's

just PR pretend for a second that I

bring this one down I'm over

exaggerating it but it's going to be you

know for the purpose of making sense

here so again what's happening to this

parietal plural it's getting pulled

away and it would also get pulled away

with the chest wall as the chest wall is

expanding as all of this is expanding

what is happening to this actual volume

here well the thoracic cavity volume is

increasing so if the volume is

increasing what will happen to the

pressure according to Bo's law the

pressure will

decrease what is the pressure in this

area the int what is intra plural

pressure so the intra plural pressure

was originally what was it originally it

was approximately

about4 mm of mercury that that's what it

was at rest so we'll put put here on the

next to it

rest but then during the inspiratory

process the volume actually went even

greater than normal because now the

actual chest wall is trying to expand

it's pulling that parietal plural away

from the actual visceral plural and this

whole volume here is increasing

potentially right it will actually get

even more negative so the pressure will

drop even more to about what

point the pressure will drop so let's

say that here we show over here what the

pressure changes to the pressure will go

from4 millim of mercury to about six

okay so it'll drop down during the

inspiratory process to about

negative 6 millimeters of mercury and

this is

during

inspiration okay sweet

deal okay next

thing as this is expanding look what

happens

here because the thoracic cavity volume

is increasing not only is that allowing

for that to happen but what happens is

these lungs want to start expanding too

so because the lungs want to start

expanding something really cool happens

this guy right here what's going to

happen to him his his actual lungs are

going to start expanding also so the

visceral plura is going to start getting

closer and closer to the parial plur

right because again we have to remember

it is a potential space but when this uh

parial plur is being pulled away by the

chest wall what is it pulling with it

it's pulling with it the visceral plural

so now what we expect to happen with

this lung now and again we're going to

drag it out out here but as long as we

get the point look at this I'm going to

bring this sucker all the way down here

what did I just do to the

lung I increased the actual volume

inside of the actual lung so if I

increase the volume inside of the lung

what does that mean for the pressure

that means that the pressure goes down

oh man should make so much sense right

so again intra pulmonary pressure what

do we say that we denoted that as we not

as that as people right we call that the

people so the people was originally what

did we say it was about NE I'm sorry not

negative it should be zero millimeters

of mercury at

rest but then what happened what did we

say the visceral plura was getting

pulled with the parietal plura as the

long as the thoracic cavity volume was

increasing due to the external

intercostals and the diaphragm so as the

volume of this actual all these alveoli

start increasing what happens to their

pressure then the pressure starts

decreasing so what should it go to then

it should drop down to appr

approximately

about -1 so it only drops about one or

two it only drops about one or two

millimeters of mercury so we're going to

put here um let's just

put1 but again it can drop down about

negative 1 or -2 so it went down one so

we're going to put negative 1

millimeters of mercury during

inspiration

oh it should make so much

sense does to me somehow all right

now now that we've done that we should

understand how those pressures have

changed but what happens to the

atmospheric pressure does anything

happen with the atmospheric pressure No

it should stay the same right it should

stay the same so the atmospheric

pressure should not be affected let's

write that down though so the

atmospheric pressure it should not be

affected okay so it should still be uh

0o millimeters of Merc if we're

comparing it right but well just for

this case we'll keep it we'll keep it

here at 760 just for the heck of it so

we'll say 760 again millimeters of

mercury and specifically this

millimeters of mercury we could also say

um as a unit we could convert it to an

atmosphere right so 760 millimet of

mercury which is actually equal to one

atmosphere so that's the same okay what

about all these other dang pressures now

what about those okay let's get to that

second let's write down what happened so

far

thoracic cavity volume increased the

third thing that happened what happened

as the thoracic cavity volume increased

what happened the intra pulmonary

pressure what happened to his pressure

it decreased what happened to the intra

plural pressure the PIP IT decreased

okay the last thing to look at is what

happens to the trans pulmonary

pressure what happens to the actual

trans thoracic pressure and if you guys

want we could even say what happens with

the trans respiratory pressure so let's

go ahead and see what happens to all of

these pressures

here

okay well the transpulmonary pressure we

said was what let's write down here real

quick here was a b c we said that the

transpulmonary pressure was the

difference from a minus B which is the

intrapulmonary pressure minus the int

plural okay well now

1 and this is -6 let's write that down

so it went from NE it's - 1 mm Mercury

minus what 6 millimeter of mercury right

minus 6 but actually should be -6 should

be -6 so

-6 millimet of mercury so it's- 1 mm

Mercury minus -6 what is that equal to

about okay well if we have -6 right so

we're taking -1 + 6 so what does that

equal to that's equal to + 5 right so it

should be + 5 mm of mercury so it went

up a little bit but like I said again

the whole point here is I said remember

it actually went down by negative 1 it

can go by down by negative 1G -2 so if

it went down byg -2 what would that be

plus 4 millim mercy so it doesn't really

change significantly but it can change a

little bit in this case all right cool

let's do the next one the next one we

said was the difference between B and C

okay well the difference between B and C

is the difference from the intra plural

pressure in the atmospheric pressure oh

we said that this a trans thoracic

pressure let's write that puppy down so

the trans thoracic pressure is equal to

the int plural pressure which we said in

this case was

-6 millimeters of mercury minus what

zero millimeters of mercury and again

what do we say that this should be the

trans thoracic pressure should be equal

to the int plural pressure and the trans

thoracic pressure is -6 millimet of

mercury what does that imply that's a

good thing that means the chests are

actually recoiling outward and as the

chest is actually the chest wall is

recoiling outward what is it doing it's

pulling on this actual what it's pulling

on the chest wall and as it pulls on the

chest wall what happens to the volume in

this area it increases so that should

make sense because this negative is that

the chest wall is actually recoiling

outward that's

good and again for the heck of it we can

do this last one here let's do this one

in red which is the difference between a

to c and that was the trans respiratory

pressure and the trans respiratory

pressure is just going to be the what

intrapulmonary which in this case was -1

millim of Mercury right minus What minus

the atmospheric pressure which in this

case is 0 millimet Mercury and in this

case what does this tell us the trans

respiratory pressure is saying that air

is actually flowing in what direction

well it was negative one here so what's

our answer here our answer is -1

millimet of mercury that's the answer

what that means

is is that air must be flowing from the

atmosphere into the alveoli that's what

the negative 1 millim Mercury is saying

it's saying that the air is Flowing from

where the air must be flowing from the

atmosphere into the alveoli if it was

positive it would be the opposite it

will be flowing out of the actual alveol

line into the

atmosphere wow this is so beautiful all

right so let's write these things down

now everything that we have here again

transpulmonary pressure should now be

about positive five millim

Mercury and then the trans thoracic

pressure should be about 6 mm

Mercury and then the actual trans

respiratory pressure we said last one

was negative

1 mm of mercury and if we want to

reiterate it the int plural pressure

actually dropped down to about what it

dropped down to actually

-6 millimeter mercury and then the

intrapulmonary pressure or the intra

avolar pressure dropped down to about 1

mm

Mercury okay these are all the events

that are occurring in Inspiration now we

have to figure out okay all this is good

and well but does our lung stay like

like this no this is basically doing

what think about this what's the

pressure inside of the Alvi what's the

pressure inside of there okay was ne1 H

negative 1 in comparison to what

negative one in comparison to the

atmosphere so in other words we could

say this is 760 and what is another way

that I could write this guys 7 59 right

I could technically write this as

759 if I wanted to now what is that that

law again that actual law boils law or

not even I'm sorry not even boils law

just the law of diffusion the law of

diffusion things like to move from areas

of high pressure to areas of low

pressure so where would the air want to

flow the air would want to flow inwards

and so

now look what happens here air starts

flowing inward as the air starts flowing

Inward and more and more and more into

the lung it'll continue to flow from the

atmosphere into the actual lungs until

the intrapulmonary pressure at the peak

point of inspiration goes until it

actually equals the atmospheric pressure

so let me say this one more time here

let me actually put it over here and

pink afterwards to write this over here

to make sure that we're clear let me

explain it one more time before I write

it

down this is negative 1 so it's 759 in

here it's a lower pressure out here is

high higher pressure things like to move

from high pressure into areas of low

pressure as this air is Flowing it's

flowing from areas of high pressure to

low pressure it will continue to flow

from the atmosphere into the actual

lungs or the alvioli in this case until

the pressure in the alvioli equals the

pressure in the atmosphere what is the

pressure in the atmosphere 760 mm of

mercury so it's going to go until it

equals 760 mm of mercury and that is

going to be at the peak point of

inspiration so while that happens when

all those events are happening when our

muscles are Contracting and all those

events the whole point is to suck air in

by pressure gradients so this will

eventually cause the intrapulmonary

pressure to equal if we say it's 760

what does that mean so what 760- 760

zero but again just so that we're clear

again what would that actually be if we

put it in the larger numbers it would be

760 because it has to reach equilibrium

with the atmosphere so this is what will

be at the peak of inspiration and then

whenever we get ready to go into ins I'm

sorry whenever we get ready to go into

expiration which we'll do in the next

video you'll see how all of these

pressures are changing again so amazing

okay all right guys so in this video we

talked a lot about the inspiratory

processes specifically with respect to

the whole mechanics of breathing okay in

the third video the next video we're

going to see exactly how all of these

events are happening again but in

Reverse specifically in expiration all

right ninja ner I'll see you soon