06 Respiratory System Physiology

7/26/2019 06 Respiratory System Physiology

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Respiratory System

PhysiologyGian Carlo Delante, PhB PTRP RPT


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Functions

Transport of oxygen

Removal of carbon dioxide

Control of blood acidity Temperature regulation

Line of defense to airborne particles


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Intrapleural Pressure

Pleural membranes Parietal pleura

Visceral pleura

Form the intrapleural space containing roughly 1!1"ml of pleural #uid

Ribs due to musclesTend to spring out$ard

Lungs due to elastinTend to recoil and collapse


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%oyle&s La$' Relationship bet$eenPressureand Volume

Volumeandpressureare inverselyproportional

Increased volume ( )))) pressure

*ecreased volume ( )))) pressure


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+uiet Inspiration' ,uscleContraction

*iaphragm Flattens and moves inferiorly

-xternal intercostal muscles -levate rib cage. moves sternum

anteriorly

Increases volumeTherefore/ pressure ))) 0


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+uiet -xpiration' ,uscle Relaxation

passive process $herein the elasticlungs and thoracic $all recoil in$ardas muscles relax

*ecreases volumeTherefore/ pressure ))) 0


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,uscles of *eep Inspiration 2-xpiration

ctivates accessory muscles to produce larger volumechanges

Deep inspiration Scalenes

Sternocleidomastoid -xternal intercostal muscles

*iaphragm

Deep expiration Internal intercostal muscles

-xternal obli3ue

Rectus abdominis

Internal obli3ue

Transversus abdominis


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Intrapulmonary PressureChanges

Intrapulmonary4intra!alveolar5pressure Pressure $ithin the alveoli

%et$een breaths e3uals atmosphericpressure

Atmosphericpressure 4sea level5 67 mm8g

Intrapleuralpressure 6"7 mm8g


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Intrapleural Pressure

Pressure $ithin the pleuralcavity

l$ays negative cts li9e a suction to 9eep

lungs in#ated

:egative intrapleuralpressure is due to'

Surface tension of alveolar#uid

-lasticity of lungs

-lasticity of thoracic $all


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-vents *uring Inspiration

Diaphragm2 external intercostalmusclescontract


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-vents *uring -xpiration

Diaphragm2 external intercostalmuscles relax


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=ther Factors ;ecting


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Resistance >ithin ir$ays

*iameter of the air$ay a;ects resistance Since gas molecules encounter resistance $hen

they stri9e the $alls of the air$ay

>hat happens during bronchoconstriction0 Resistance increases or decreases0

>hat happens during an increased

resistance0 ir#o$ increases or decreases0

Therefore'


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Factors ;ecting ir$ayResistance

Several factors change air$ay resistance bya;ecting the diameter of air$ays %y contractingor relaxingsmooth muscle in

air$ay $alls/ esp? bronchioles

Parasympathetic neurons Release acetylcholine$hich constricts

bronchioles

"istamine Constricts bronchioles

#pinephrine *ilates bronchioles


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Lung Compliance' -lasticFibers

The ease $ith $hich the lungs expand

*etermined by t$o factors' $a% &tretchailityo' elastic (ers $ithin the lungs

$%The sur'ace tension $ithin the alveoli

4a5 &tretchailityo' elastic (ers $ithin thelungs

8ealthy lungs 8igh compliance

Fibrosis Less #exible CT develops. lo$ compliance


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Lung Compliance' SurfaceTension

4b5 The sur'ace tension $ithin thealveoli

Some premature infants do notproduce surfactant @ highor lowcompliance0 Surfactant lo)erssurface tension 2

increaseslung compliance


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Pulmonary Surfactant

type of lipoprotein

Secreted by type II alveolar cells

Produced in the lungs even e'orethe baby is born


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Summary

,uscle activity causes changes in the volume of thethoracic cavity during breathing

Changing the thoracic cavity volume causesintrapulmonaryand intrapleural pressurechanges/ $hich allo$ air to move from high pressure

to lo$ pressure regions ir$ay resistance is normally lo$/ but nervous

stimulation and chemical factors can change thediameter of bronchioles/ thereby altering resistance

and air#o$ !ung compliance is normally highdue to the

lung&s abundant elastic tissue and sur'actant*sability to lower the surface tension of the alveolar#uid


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Aas -xchange

Dalton*s !a) of Partial Pressure In a mixture of gases/ the total pressure

e3uals the sum of the partial pressure

exerted by each gas tmospheric pressure 4sea level5 ( +-

mm"g =xygen' B?D x 67 ( 1"mm8g

Carbon dioxide' ?ED x 67 ( ?mm8g

:itrogen' 6G?7D x 67 ( "6mm8g

>ater' ?E7D x 67 ( ?"mm8g


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-;ects of 8igh ltitude onPartial Pressures

1E/" feet above sea level (..-mm"g =xygen' B?D x EE ( B mm8g

Carbon dioxide' ?ED x EE ( ?Bmm8g

:itrogen' 6G?7D x EE ( E7 mm8g

>ater' ?E7D x EE ( B mm8g t high altitudes partial pressure of

all gases are lo)erthan at sea level


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8enry&s La$

The amount of gas $hich dissolves ina li3uid is proportionalto'The partial pressure of the gas

The soluilityof the gas


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Sites of Aas -xchange

#xternal respiration C=B di;uses from

pulmonary capillaries intoalveoli

=B di;uses from alveoliinto pulmonary capillaries

Internal respiration =B di;uses from systemic

capillaries into cells C=B di;uses from cells

into systemic capillaries


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-xternal Respiration' PartialPressures

The partial pressures ofgases in the alveolidi/erfrom those in theatmosphere

*i;erence caused bythese factors' 8umidiHcation of inhaled

air

Aas exchange bet$eenalveoli and pulmonarycapillaries

,ixing of ne$ and old air


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-xternal Respiration' nloading C=B

C=B di;uses along its partialpressure gradient/ from the bloodinto the alveolus/ until e3uilibrium is

reached


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-xternal Respiration'=B 2 C=B -xchange

Carbon dioxide is very solule in blood/allo$ing many molecules to di;use alongthis small partial pressure gradient

=xygen is less solule/ re3uiring a largerpressure gradient


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Internal Respiration'=B 2 C=B -xchange

Aas exchange continues untile3uilibrium is reached


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Summary Aas la$s sho$ the relationship bet$een partial pressure/

soluility/ and concentrationof gases

Aases di;use along their partial pressure gradients/ fromregions of high partial pressure to regions o' lo)partial pressure

#xternal respiration' =B loads from alveoli into pulmonarycapillaries/ and C=B unloads from pulmonary capillaries intoalveoli

Internal respiration' =B unloads from systemic capillariesinto cells/ and C=B loads from cells into systemic capillaries

-Jcient gas exchange depends on several factors includingsur'ace area/ partial pressure gradients/ lood 3o)and air3o)

*uring external respiration/ ventilation4per'usioncoupling maintains air#o$ and blood #o$ in proper

proportions for eJcient gas exchange


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Lung


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Capacities

Inspiratory capacity' The maximum amount of airthat can be inhaled after exhaling the tidal volume4e3uals tidal volume K inspiratory reserve volume5

5unctional residual capacity' The amount of airstill in the lungs after exhalation of the tidal volume

4e3uals expiratory reserve volume K residual volume5

Vital capacity' The maximum amount of air that canbe exhaled after a maximal inhalation 4e3ualsinspiratory reserve volume K tidal volume K

expiratory reserve volume5 Total lung capacity' The maximum amount of air

that lungs can hold 4e3ual to vital capacity K residualvolume5


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Lung


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ones

Conducting 6ones M' anatomical dead space

Anatomical dead space volume7 89- ml

rea of the lungs $here no gasexchange ta9es place 4because thereare no alveoli5

Respiratory 6ones Region of the lungs $here alveoli are

located

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06 Respiratory System Physiology