Respiratory SystemRespiratory System Internal respiration “cellular”: internal metabolic Internal respiration “cellular”: internal metabolic

process carried out within the mitochondria:process carried out within the mitochondria: OO22+nutrients+nutrients CO CO22+energy+energy

External respiration: all events that are External respiration: all events that are responsible for the exchange of Oresponsible for the exchange of O22 & CO & CO22 between the external environment and cells, it between the external environment and cells, it occurs in 4 steps:occurs in 4 steps:

1-breathing (ventilation)1-breathing (ventilation) 2-gas diffusion between alveoli and blood2-gas diffusion between alveoli and blood 3-transport of gases by blood3-transport of gases by blood 4-gas diffusion between capillary & tissue4-gas diffusion between capillary & tissue

Fig. 12-1, p. 366

Atmosphere

Tissue cell

Alveoli of lungs

Pulmonarycirculation

Systemiccirculation

CO2O2

Food + O2 CO2 + HO2 + HTP

O2

CO2

CO2

O2

1

Steps of external respiration

Ventilation or gas exchange betweenthe atmosphere and air sacs (alveoli)in the lungs

Exchange of O2 and CO2 between air

in the alveoli and the blood

Transport of O2 and CO2 between the

lungs and the tissues

Exchange of O2 and CO2 between the

blood and the tissuesInternal respiration

2

3

4

Non-respiratory functions of the system:Non-respiratory functions of the system: 1-water loss and heat elimination, also 1-water loss and heat elimination, also

keeps alveoli wetkeeps alveoli wet 2-inhances venous return2-inhances venous return 3-acid-base balance3-acid-base balance 4-enables speech4-enables speech 5-defends against foreign inhaled matters.5-defends against foreign inhaled matters. 6-removes, modifies, & activate or 6-removes, modifies, & activate or

inactivate materials “prostglandins”inactivate materials “prostglandins” 7-smelling7-smelling 8-shape of the chest8-shape of the chest 9-protects heart & vessels9-protects heart & vessels 10-aireate the blood between respiratory 10-aireate the blood between respiratory

phasesphases

Respiratory airwaysRespiratory airways

Nose Nose pharynx (throat) pharynx (throat) trachea trachea (windpipe)(windpipe)

Larynx at the entrance of tracheaLarynx at the entrance of trachea

Two main branches (bronchi) Two main branches (bronchi) branches branches bronchioles bronchioles

Fig. 12-2a, p. 367

Nasalpassages

Mouth

Pharynx

Larynx

Trachea

Cartilaginousring

Rightbronchus

Bronchiole

Terminalbronchiole

Terminalbronchiole

Respiratorybronchiole

Alveolar sac

(continue to next slide)

lungslungs

Alveoli : clustered thin walled Alveoli : clustered thin walled inflatable grape like sacs ( thin layer inflatable grape like sacs ( thin layer of type I alveolar cells)of type I alveolar cells)

Interstitial space very thin ~ 0.5 MmInterstitial space very thin ~ 0.5 Mm 300 million alveoli, each 300 Mm 300 million alveoli, each 300 Mm

diameter, surface area over 75mdiameter, surface area over 75m Type II alveolar cells secrete Type II alveolar cells secrete

pulmonary surfactant pulmonary surfactant Alveolar macrophagesAlveolar macrophages

2

Fig. 12-2b, p. 367

Terminalbronchiole

Respiratorybronchiole

Branch ofpulmonaryartery

Alveolus

Pores of Kohn

Smoothmuscle

Branch ofpulmonaryvein

Pulmonarycapillaries

Alveolarsac

Pleural sacPleural sac

Double walled, closed, separates Double walled, closed, separates lungs from the thoracic wall and lungs from the thoracic wall and other surrounding structuresother surrounding structures

Pleural cavity, intrapleural fluidPleural cavity, intrapleural fluid

Respiratory mechanicsRespiratory mechanics

Air moves by pressure gradient:Air moves by pressure gradient:

1-atmospheric (barometric) pressure 1-atmospheric (barometric) pressure 760mmHg at sea level760mmHg at sea level

2-intra-alveolar pressure “no air 2-intra-alveolar pressure “no air flow” = atmospheric pressureflow” = atmospheric pressure

3-intrapleural pressure is less than 3-intrapleural pressure is less than atmospheric ~ 756 mmHg atmospheric ~ 756 mmHg

Fig. 12-5, p. 370

Atmosphere760 mm Hg

Atmospheric pressure (the pressureexerted by the weight of the gas in theatmosphere on objects on the Earth’s surface—760 mm Hg at sea level)

Intra-alveolar pressure (the pressure withinthe alveoli—760 mm Hg when equilibratedwith atmospheric pressure)

Intrapleural pressure (the pressure within the pleural sac—the pressure exerted outside the lungs within the thoracic cavity, usually less than atmospheric pressure at 756 mm Hg)

Airways

Thoracic wall

Plural wall

Lungs

756 mm Hg

The lungs are stretched to fill the thorax The lungs are stretched to fill the thorax because: because:

a- intrapleural fluids cohesivenessa- intrapleural fluids cohesiveness

b- transmural pr. Gradientb- transmural pr. Gradient

Pneumothorax: abnormal condition, air Pneumothorax: abnormal condition, air in the pleura so there’s no transmural in the pleura so there’s no transmural pr. gradient so no force to stretch the pr. gradient so no force to stretch the lungslungs collapse collapse

Fig. 12-8a, p. 371

Puncture woundin chest wall

760

760 760

Traumatic pneumothorax

760

756

760

756

(Continue to the next slide)

Numbers are mm Hg pressure.

Fig. 12-8b, p. 371

760

760 760

Collapsed lung

760 760

756

(Continue to the next slide)

760

Numbers are mm Hg pressure.

Air flowAir flow

Boyle’s law at constant temperature : Boyle’s law at constant temperature : partial pressure of a gas varies partial pressure of a gas varies inversely with the volume of the gasinversely with the volume of the gas

Respiratory muscles change the Respiratory muscles change the thoracic cavity volume which causes thoracic cavity volume which causes lung volume changelung volume change

Inspiration & expiration ( one breath) Inspiration & expiration ( one breath) are the respiratory cycle. are the respiratory cycle.

Fig. 12-12a, p. 374

Equilibrated;no net movement of air

760

Preinspiratorysize of thorax

Preinspiratorysize of lungs

756

Before inspiration

Respiratory muscelsRespiratory muscels

Major inspiration muscles:Major inspiration muscles:

a- diaphragm b- external a- diaphragm b- external intercostalsintercostals

Accessory inspiration muscles:Accessory inspiration muscles:

a- sternocleidomastoid b- scalenusa- sternocleidomastoid b- scalenus

Expiratory muscles:Expiratory muscles:

a- abdominal muscles b- internal a- abdominal muscles b- internal intercostals intercostals

Fig. 12-11a, p. 374

Externalintercostalmuscles(relaxed)

Contractions of external intercostalmuscles causes elevation of ribs,which increases side-to-sidedimension of thoracic cavity

Lowering of diaphragm oncontraction increases verticaldimension of thoracic cavity

Elevation of ribs causes sternumto move upward and outward, which increases front-to-back dimension of thoracic cavity

Before inspiration Inspiration

Elevatedrib cage

Contractionof externalintercostalmuscles

Sternum

Diaphragm(relaxed)

Contractionof diaphragm

Fig. 12-11bc, p. 375

Relaxationof externalintercostalmuscles

Return of diaphragm, ribs, and sternum to resting position on relaxation of inspiratory muscles restores thoracic cavity to preinspiratory size

Contractions of abdominalmuscles cause diaphragm tobe pushed upward, furtherreducing vertical dimension of thoracic cavity

Contraction of internal intercostal muscles flattens ribs and sternum, further reducingside-to-side and front-to-back dimensions of thoracic cavity

Passive expiration

Active expiration

Contractionof internalintercostalmuscles

Relaxation ofdiaphragm

Contractionof diaphragm

Position of relaxedabdominal muscles

Elastic behavior of the lungElastic behavior of the lung Compliance: how much effort is Compliance: how much effort is

required to stretch or distend the lung “ required to stretch or distend the lung “ how much volume change occurs in the how much volume change occurs in the lung from a given change in the lung from a given change in the transmural pr. gradient transmural pr. gradient

Pulmonary elastic behavior depends on:Pulmonary elastic behavior depends on: 1-pulmonary elastic connective tissue: 1-pulmonary elastic connective tissue:

large quantity of elastin fibers, they large quantity of elastin fibers, they tend to bounce back lungs to their tend to bounce back lungs to their original shapeoriginal shape

2- Alveolar surface tension: 2- Alveolar surface tension: thin liquid film that lines the alveolithin liquid film that lines the alveoli unique attraction between water unique attraction between water

molecules at the air-water interfacemolecules at the air-water interface attraction creates surface tension which attraction creates surface tension which

opposes the expansion of the alveoli and opposes the expansion of the alveoli and tends to shrink themtends to shrink them

pulmonary surfactant: mixture of lipids & pulmonary surfactant: mixture of lipids & proteins secreted from type II cells, it proteins secreted from type II cells, it lowers alveolar surface tension so it lowers alveolar surface tension so it increases lung compliance & reduces lung increases lung compliance & reduces lung tendency to recoil so no collapsetendency to recoil so no collapse

newborn respiratory distress syndrome is newborn respiratory distress syndrome is treated by surfactant and drugs for treated by surfactant and drugs for maturation processmaturation process

Lungs volume & capacitiesLungs volume & capacities Tidal volume -500mL- (TV)Tidal volume -500mL- (TV) Inspiratory reserve volume -3000mL- : extra volume Inspiratory reserve volume -3000mL- : extra volume

can be maximally inspired over & above TV (IRV)can be maximally inspired over & above TV (IRV) Inspiratory capacity -3500mL- : maximum volume the Inspiratory capacity -3500mL- : maximum volume the

can be inspired at the end of normal quite expiration can be inspired at the end of normal quite expiration (IC)(IC)

Expiratory reserve volume -1000mL- :extra volume Expiratory reserve volume -1000mL- :extra volume that can be actively expired by maximally that can be actively expired by maximally contracting the expiratory muscles beyond that contracting the expiratory muscles beyond that normally passively expired (ERV)normally passively expired (ERV)

Residual volume -1200mL- : minimum volume Residual volume -1200mL- : minimum volume remaining in the lung after maxim expiration (RV)remaining in the lung after maxim expiration (RV)

Functional residual capacity -2200mL- : volume in Functional residual capacity -2200mL- : volume in lungs at the end of quite passive expiration lungs at the end of quite passive expiration “ERV+RV” (FRV) “ERV+RV” (FRV)

Vital capacity -4500mL- : maximum air that Vital capacity -4500mL- : maximum air that can be moved after maximum inspiration can be moved after maximum inspiration (VC)(VC)

Total lung capacity -5700mL- (TLC)Total lung capacity -5700mL- (TLC)

Forced expiratory volume in 1 sec. (FEV1) : Forced expiratory volume in 1 sec. (FEV1) : volume of air in first second of vital capacity volume of air in first second of vital capacity determination , normally = 80% of VC determination , normally = 80% of VC

Lungs volume & capacitiesLungs volume & capacities

Fig. 12-14b, p. 378

TV = Tidal volume (500ml)IRV = Inspiratory reserve volume (3,000 ml)IC = Inspiratory capacity (3,500 ml)ERV = Expiratory reserve volume (1,000 ml)RV = Residual volume (1,200 ml)FRC = Functional residual capacity (2,200 ml)VC = Vital capacity (4,500 ml)TLC = Total lung capacity (5,700 ml)

Alveolar ventilation: volume of air exchanged Alveolar ventilation: volume of air exchanged between atmosphere & alveoli per minutebetween atmosphere & alveoli per minute

Pulmonary ventilation: volume of air breathed in Pulmonary ventilation: volume of air breathed in & out in one minute = TV x respiratory rate = & out in one minute = TV x respiratory rate = 500 x 12 = 6000 mL/min.500 x 12 = 6000 mL/min.

Anatomic dead space: volume of airway Anatomic dead space: volume of airway conducting channels ~ 150mLconducting channels ~ 150mL

Alveolar ventilation rate= (TV – DS) x res. rate = Alveolar ventilation rate= (TV – DS) x res. rate =

(500-150) x 12 = 4200 mL/min(500-150) x 12 = 4200 mL/min Alveolar dead space: ventilated alveoli that do Alveolar dead space: ventilated alveoli that do

not participate in gas exchange with blood not participate in gas exchange with blood because they are inadequately perfused, because they are inadequately perfused, normally not significantnormally not significant

Gas exchangeGas exchange

Partial pressure of gasses :Partial pressure of gasses :

dry atmospheric air contains 79% N, dry atmospheric air contains 79% N, 21% O21% O22, ~0% CO, ~0% CO22, ~0% H, ~0% H22O vaporO vapor

the partial pressure of the gas is the partial pressure of the gas is directly proportional to the % of that directly proportional to the % of that gas in the mixturegas in the mixture

PPNN22=600 mmHg P=600 mmHg POO22=160 mmHg =160 mmHg

PPCOCO22= 0.023 mmHg = 0.023 mmHg

Partial pr. In liquid: the more the gas is Partial pr. In liquid: the more the gas is dissolved the more the partial pr. Is in itdissolved the more the partial pr. Is in it

Alveolar air: Alveolar air:

PPOO22=100 mmHg atmospheric=160 =100 mmHg atmospheric=160 mmHg because HmmHg because H22O vapor replaces O vapor replaces some of the Osome of the O22 and the fresh air is and the fresh air is mixed with old alveolar airmixed with old alveolar air

PPCOCO22=40 mmHg through the =40 mmHg through the respiratory cycle because COrespiratory cycle because CO22 diffuses diffuses from blood at the same time removed from blood at the same time removed continuously out. continuously out.

Arterial blood in lungs contains 40 Arterial blood in lungs contains 40 mmHg OmmHg O22 , 46 mmHg CO , 46 mmHg CO22

Capillary blood equilibrates with alveoli Capillary blood equilibrates with alveoli P POO22= 100 mmHg, P= 100 mmHg, PCOCO22=40mmHg=40mmHg

Surface area, thickness of membrane, Surface area, thickness of membrane, could change the diffusion rate but could change the diffusion rate but healthy persons have constant surface healthy persons have constant surface area & thicknessarea & thickness

emphysema, pulmonary edema, emphysema, pulmonary edema, pulmonary fibrosis, pneumonia pulmonary fibrosis, pneumonia

Gas transportGas transport OO22 in blood is transported in 2 forms: in blood is transported in 2 forms:

physically dissolved & chemically bound to physically dissolved & chemically bound to HbHb

3mL O3mL O22 is dissolved in 1L blood at P is dissolved in 1L blood at POO22=100 =100 mmHG so total blood has 15mL OmmHG so total blood has 15mL O22 dissolved equivalent to 1.5% of total Odissolved equivalent to 1.5% of total O22 in in blood so 98.5% is boundblood so 98.5% is bound

PPOO22 in blood represents the dissolved in blood represents the dissolved portion onlyportion only

Reduced hemoglobin (deoxyhemoglobin)Reduced hemoglobin (deoxyhemoglobin) PPOO22 is important to determine the % of Hb is important to determine the % of Hb

saturation of Osaturation of O22

Fig. 12-22, p. 388

Average restingPO2 at systemic

capillaries

Normal PO2 at pulmonarycapillaries

Hb Hb 4 molecules of O 4 molecules of O22

OO22-Hb dissociation curve is S-shaped-Hb dissociation curve is S-shaped

The significance of the plateau portion:The significance of the plateau portion:

1- when the alveolar P1- when the alveolar POO22 decreases down decreases down to 60 mmHg it will not affect the amount to 60 mmHg it will not affect the amount of Oof O22 in the blood in the blood

2- when breathing pure O2- when breathing pure O22 (600mmHg) (600mmHg) 100% saturation, so the rang between 100% saturation, so the rang between 60mmHg – 100mmHg gives only 10% 60mmHg – 100mmHg gives only 10% difference in saturationdifference in saturation

The significance of the steep portion:The significance of the steep portion:

1- at 40mmHg which is the average 1- at 40mmHg which is the average PPOO22 in the capillary blood the Hb in the capillary blood the Hb saturation is 75% so 25% leavessaturation is 75% so 25% leaves

2- if the metabolism is high the P2- if the metabolism is high the POO22 from capillaries to the veins will not be from capillaries to the veins will not be 40 mmHg it will go down to 20 or less, 40 mmHg it will go down to 20 or less, at that level the saturation goes down at that level the saturation goes down to 30% so more than 45% Oto 30% so more than 45% O22 is is released released a small drop in the a small drop in the systemic capillary COsystemic capillary CO22 can make large can make large amount of Oamount of O22 diffusion to tissues diffusion to tissues

Factors affecting Hb affinity:Factors affecting Hb affinity:

1- CO1- CO22 : if increases : if increases shift to right shift to right

2- pH : if decreases2- pH : if decreases shift to right shift to right

3- temp. :if increases 3- temp. :if increases shift to right shift to right

4- 2,3 bisphosphoglycerate : if increases 4- 2,3 bisphosphoglycerate : if increases shift to right shift to right

Factors concentration differ in the Factors concentration differ in the pulmonary circulation from the systemic pulmonary circulation from the systemic circulation circulation

Hb affinity to CO is 240 times it affinity to Hb affinity to CO is 240 times it affinity to OO22 HbCO is called carboxyhemoglobin HbCO is called carboxyhemoglobin

Fig. 12-24, p. 391

Arterial PCO2 and acidity,normal body temperature(as at pulmonary level)

PCO2 Acid (H+)

Temperatureor2,3-Bisphosphoglycerate

(as attissuelevel)

COCO22 is mainly transported as is mainly transported as bicarbonate in 3 forms: bicarbonate in 3 forms:

a- physically dissolved 10%a- physically dissolved 10%

b- bound to Hb 30%b- bound to Hb 30%

c- HCOc- HCO33 60% 60%

HH22O + COO + CO22 H H22COCO33 H + HCO H + HCO33

-

-+

Control of respirationControl of respiration

nervous control:nervous control:

-respiratory center in brain stem:-respiratory center in brain stem:

1-primary control centre: medullary 1-primary control centre: medullary respiratory center (aggregation of respiratory center (aggregation of neuronal cell bodies)neuronal cell bodies)

2-apneustic center & pneumotaxic 2-apneustic center & pneumotaxic centre: in pons and they influence the centre: in pons and they influence the output from the primary control center output from the primary control center

Fig. 12-26, p. 396

Pons

Pneumotaxic centerApneustic center

Pre-Bötzingercomplex

Dorsal respiratorygroup

Ventral respiratorygroup Medulla

Ponsrespiratorycenters

Medullaryrespiratorycenter

Respiratorycontrolcenters inbrain stem

Medullary center has:Medullary center has:

1-dorsal respiratory group (DRG) : contains 1-dorsal respiratory group (DRG) : contains only inspiratory neurons “quite breathing”only inspiratory neurons “quite breathing”

2-ventral respiratory group (VRG) : has 2-ventral respiratory group (VRG) : has inspiratory & expiratory neurons “active inspiratory & expiratory neurons “active inspiration & expiration”inspiration & expiration”

Generation of respiratory rhythm is by the Generation of respiratory rhythm is by the pre-botzinger complex located near the pre-botzinger complex located near the upper end of the medullary centre “as a upper end of the medullary centre “as a pacemaker activity”pacemaker activity”

Apneustic & pneumotaxic centers: fine Apneustic & pneumotaxic centers: fine tuning influences:tuning influences:

-pneumotaxic : switches off inspiratory -pneumotaxic : switches off inspiratory neurons limiting the time of inspirationneurons limiting the time of inspiration

-apneustic : prevents the switching of -apneustic : prevents the switching of inspiratory neurons so it provides extra inspiratory neurons so it provides extra boost to the inspiratory driveboost to the inspiratory drive

Hering-breuer reflex: when TV is larger Hering-breuer reflex: when TV is larger than 1L, pulmonary stretch receptors than 1L, pulmonary stretch receptors within the smooth muscles of the airways within the smooth muscles of the airways signals to afferent nerves to the medullary signals to afferent nerves to the medullary center to inhibt respiration center to inhibt respiration

Control of respirationControl of respiration Chemical control:Chemical control: 1-decrement of P1-decrement of POO22 is sensed by arterial & is sensed by arterial &

peripheral chemoreceptors (carotid bodies & peripheral chemoreceptors (carotid bodies & aortic bodies) which leads to increment in the aortic bodies) which leads to increment in the ventilation.ventilation.

increment in H concentration in the arterial increment in H concentration in the arterial blood will stimulate the bodiesblood will stimulate the bodies the threshold for stimulation is high when the threshold for stimulation is high when PPOO22 is higher than 60mmHg because until 60 is higher than 60mmHg because until 60 mmHg the Hb saturation is still 90%mmHg the Hb saturation is still 90% very low Pvery low POO22 could depress the respiratory could depress the respiratory centre instead of increasing ventilation centre instead of increasing ventilation

+

Fig. 12-27, p. 397

Sensory nerve fiber

Carotid sinus

Carotid artery

Aortic arch

Sensory nerve fiber

Carotid bodies

Aortic bodies

Heart

2- CO2- CO2 2 generated H and arterial PCOgenerated H and arterial PCO22 changes changes significantly increase ventilationsignificantly increase ventilation

peripheral receptors do not respond peripheral receptors do not respond to PCOto PCO22 increment increment central receptors in the medulla central receptors in the medulla monitor [H+] in the ECFmonitor [H+] in the ECF H+ cannot pass the blood-brain barrier while H+ cannot pass the blood-brain barrier while

the COthe CO22 can so : can so :↑ ↑ art. COart. CO22 ↑ CO ↑ CO22 in ECF in ECF ( H( H22O + COO + CO22 H H22COCO33

H + HCO H + HCO33)) very high CO2 “more than 80 mmHg”

depresses the respiratory center

+

-

+

Fig. 12-28, p. 398

Arterial PCO2Relieves

Brain ECF PCO2

Brain ECF H+

Centralchemoreceptors

Medullaryrespiratory

center

Ventilation

Arterial PCO2

Peripheralchemoreceptors

Weakly

(whenarterial

PCO2

>70-80mm Hg)

Brain ECF

ca = Carbonic anhydrase

The EndThe End