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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