Structure and Function of the Pulmonary System Chapter 32 Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc

Structure and Function of the Structure and Function of the Pulmonary SystemPulmonary System

Chapter 32Chapter 32

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.

22Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.

Structures of the Structures of the Pulmonary SystemPulmonary System

AirwaysAirways Blood vesselsBlood vessels Chest wall Chest wall LungsLungs

LobesLobes SegmentsSegments Lobules Lobules


Structures of the Pulmonary SystemStructures of the Pulmonary System



Conducting airwaysConducting airways Upper airwaysUpper airways

• NasopharynxNasopharynx• OropharynxOropharynx

LarynxLarynx• Connects upper and lower airwaysConnects upper and lower airways

Lower airwaysLower airways• TracheaTrachea• BronchiBronchi• Terminal bronchiolesTerminal bronchioles





Gas-exchange airwaysGas-exchange airways Respiratory bronchiolesRespiratory bronchioles Alveolar ductsAlveolar ducts Alveoli Alveoli

• Epithelial cellsEpithelial cells Type I alveolar cellsType I alveolar cells

– Alveolar structureAlveolar structure Type II alveolar cellsType II alveolar cells

– Surfactant productionSurfactant production








Gas ExchangeGas Exchange AlveoliAlveoli

Primary gas-exchange units Primary gas-exchange units Pores of KohnPores of Kohn

• Permit air to pass through the septa from alveolus to alveolusPermit air to pass through the septa from alveolus to alveolus Collateral ventilation and even air distribution Collateral ventilation and even air distribution

Lungs contain approximately 25 million alveoli at Lungs contain approximately 25 million alveoli at birth and 300 million by adulthoodbirth and 300 million by adulthood


Pulmonary and Pulmonary and Bronchial CirculationBronchial Circulation

Pulmonary circulation has a lower pressure Pulmonary circulation has a lower pressure than systemic circulation (18 mmHg)than systemic circulation (18 mmHg)

Only one third of vessels filled with blood at Only one third of vessels filled with blood at any given timeany given time



Pulmonary artery divides and enters the lung Pulmonary artery divides and enters the lung at the hilusat the hilus

Each bronchus and bronchiole has an Each bronchus and bronchiole has an accompanying artery or arterioleaccompanying artery or arteriole


Pulmonary and Bronchial Pulmonary and Bronchial CirculationCirculation



Alveolocapillary membraneAlveolocapillary membrane Formed by shared alveolar and capillary wallsFormed by shared alveolar and capillary walls Thin membrane of alveolar epithelium, the alveolar Thin membrane of alveolar epithelium, the alveolar

basement membrane, interstitial space, the basement membrane, interstitial space, the capillary basement membrane, and the capillary capillary basement membrane, and the capillary endotheliumendothelium


Pulmonary and Bronchial CirculationPulmonary and Bronchial Circulation


Chest Wall and PleuraChest Wall and Pleura Chest wallChest wall

Skin, ribs, and intercostal musclesSkin, ribs, and intercostal muscles Thoracic cavityThoracic cavity

PleuraPleura Serous membraneSerous membrane Parietal and visceral layersParietal and visceral layers Pleural space (cavity)Pleural space (cavity) Pleural fluidPleural fluid


Lung FunctionsLung Functions Gas exchangeGas exchange

Supply oxygenSupply oxygen Eliminate COEliminate CO22

Maintain pHMaintain pH Eliminate waterEliminate water Other functionsOther functions

Maintain normal body temperatureMaintain normal body temperature Immune responsesImmune responses Hormone secretionHormone secretion MetabolismMetabolism


Requirements for Ventilation, Requirements for Ventilation, Perfusion, and DiffusionPerfusion, and Diffusion

Adequate inspired OAdequate inspired O22 – (Fi – (FiOO22)) Ventilation and perfusion of alveoliVentilation and perfusion of alveoli A permeable alveolocapillary membraneA permeable alveolocapillary membrane Adequate blood flowAdequate blood flow Ability to transport OAbility to transport O22 and CO and CO22

Ability of cell to use OAbility of cell to use O22 and eliminate CO and eliminate CO22


Requirements for Ventilation, Requirements for Ventilation, Perfusion, and DiffusionPerfusion, and Diffusion

Adequate inspired OAdequate inspired O22 – (FiO – (FiO22))

Barometric pressure is 760 at sea level Barometric pressure is 760 at sea level

21% x 760 = partial pressure of O21% x 760 = partial pressure of O22 at sea level at sea level = ~160 mmHg= ~160 mmHg

Barometric pressure is 600 at Salt Lake City Barometric pressure is 600 at Salt Lake City (much lower on Mt. Everest) (much lower on Mt. Everest)

21% x 600 = partial pressure of O21% x 600 = partial pressure of O22 at SLC at SLC = ~126 mmHg = ~126 mmHg

Why we give oxygen at high altitudeWhy we give oxygen at high altitude


Function of the Pulmonary Function of the Pulmonary SystemSystem

VentilationVentilation Mechanical movement of gas or air into and out of Mechanical movement of gas or air into and out of

the lungsthe lungs Minute volumeMinute volume

• Ventilatory rate multiplied by the volume of air per breathVentilatory rate multiplied by the volume of air per breath

Alveolar ventilationAlveolar ventilation


Lung Volumes and CapacitiesLung Volumes and CapacitiesBased on Age, Gender, HeightBased on Age, Gender, Height

Dead space: oropharynx to division 16 (about Dead space: oropharynx to division 16 (about equal to ideal body weight)equal to ideal body weight)

Tidal volume (per breath) 400-800 mlTidal volume (per breath) 400-800 ml IRV 3000 ml additional air that could be inhaledIRV 3000 ml additional air that could be inhaled


Lung Volumes and CapacitiesLung Volumes and CapacitiesBased on Age, Gender, HeightBased on Age, Gender, Height

ERV 1000 ml remaining air ERV 1000 ml remaining air Can be forcefully expired after normal expiration FEVCan be forcefully expired after normal expiration FEV11

Why abdominal thrusts work; expel TV plus ERVWhy abdominal thrusts work; expel TV plus ERV Forced vital capacity (theoretical) Forced vital capacity (theoretical)

TV + IRV + ERV ~4500-5000 ml TV + IRV + ERV ~4500-5000 ml Residual volume constant ~1200 ml Residual volume constant ~1200 ml

Air remaining in alveoliAir remaining in alveoli


FormulasFormulas

Minute ventilation (or volume/min) Minute ventilation (or volume/min) RR x TV RR x TV RR 16, TV 500 RR 16, TV 500 16 x 500 = 8000 ml/min16 x 500 = 8000 ml/min

Effective minute volume: RR x (TV-DS) Effective minute volume: RR x (TV-DS) 100 lb, RR 16, TV 500 ml100 lb, RR 16, TV 500 ml 16 (500-100) = 6400 ml/min16 (500-100) = 6400 ml/min


Control of VentilationControl of Ventilation

ANSANS Stimulates smooth muscle (contract relax)Stimulates smooth muscle (contract relax)

• Airway lumen diameterAirway lumen diameter


TermsTerms

HypoxiaHypoxia Low oxygen in the cellLow oxygen in the cell

HypoxemiaHypoxemia Low oxygen in arterial blood (low OLow oxygen in arterial blood (low O22 saturation) saturation)



ChemoreceptorsChemoreceptors Central receptorsCentral receptors

• Reflects PaReflects PaCOCO22

• Stimulated by HStimulated by H++ in cerebrospinal fluid (pH) in cerebrospinal fluid (pH)

Peripheral receptorsPeripheral receptors• Aorta and carotid bodiesAorta and carotid bodies

• Stimulated by hypoxemia (PaStimulated by hypoxemia (PaOO22))



Irritant receptors: epithelium of conducting Irritant receptors: epithelium of conducting airwaysairways Cough, bronchoconstriction, decrease RRCough, bronchoconstriction, decrease RR

Stretch receptors: protectiveStretch receptors: protective Decrease RR and volumeDecrease RR and volume


VentilationVentilation Neurochemical controlNeurochemical control

Respiratory centerRespiratory center• Dorsal respiratory groupDorsal respiratory group

• Ventral respiratory groupVentral respiratory group

• Pneumotaxic centerPneumotaxic center

• Apneustic centerApneustic center

Peripheral chemoreceptorsPeripheral chemoreceptors


VentilationVentilation Neurochemical controlNeurochemical control

Lung receptorsLung receptors• Irritant receptorsIrritant receptors

• Stretch receptorsStretch receptors

• J-receptorsJ-receptors

ChemoreceptorsChemoreceptors• Central chemoreceptorsCentral chemoreceptors

• Peripheral chemoreceptorsPeripheral chemoreceptors


Mechanics of BreathingMechanics of Breathing Major and accessory musclesMajor and accessory muscles

Major muscles of inspirationMajor muscles of inspiration• DiaphragmDiaphragm

• External intercostalsExternal intercostals

Accessory muscles of inspirationAccessory muscles of inspiration• Sternocleidomastoid and scalene musclesSternocleidomastoid and scalene muscles

Accessory muscles of expirationAccessory muscles of expiration• Abdominal and internal intercostal musclesAbdominal and internal intercostal muscles


Muscles of VentilationMuscles of Ventilation


Overview: Mechanics of BreathingOverview: Mechanics of Breathing Alveolar surface tensionAlveolar surface tension

Function of surfactantFunction of surfactant Elastic properties of lung and chest wallElastic properties of lung and chest wall

Elastic recoilElastic recoil ComplianceCompliance

Airway resistance Airway resistance Airway size Airway size Gas velocity (Poiseuille’s law)Gas velocity (Poiseuille’s law)

Muscular effortMuscular effort


Mechanics of BreathingMechanics of Breathing


Surface Tension of WaterSurface Tension of Water Tendency of water molecules to Tendency of water molecules to contractcontract to the to the

smallest possible surface area (bead) with smallest possible surface area (bead) with exposure to airexposure to air

Increased surface tension = increased work of Increased surface tension = increased work of breathingbreathing


Laplace’s LawLaplace’s Law The smaller a sphere’s radius (alveoli) the The smaller a sphere’s radius (alveoli) the

greater the surface tension and the more difficult greater the surface tension and the more difficult (work) to expand the alveoli (work) to expand the alveoli

P = 2t/rP = 2t/r P = pressure inside a sphere (alveoli)P = pressure inside a sphere (alveoli) t = surface tensiont = surface tension r = radius of a spherer = radius of a sphere

Surfactant reduces fluid surface tension lining Surfactant reduces fluid surface tension lining the alveoli and decreases tendency to collapse, the alveoli and decreases tendency to collapse, preventing atelectasispreventing atelectasis


ComplianceCompliance A measure of lung and chest wall distensibility or A measure of lung and chest wall distensibility or

“stiffness” “stiffness”

― ― volume of air movedvolume of air moved

― ― force to move the airforce to move the air Low: increased work of inspirationLow: increased work of inspiration

Stiff lungsStiff lungs High: increased work of expirationHigh: increased work of expiration

Baggy lungsBaggy lungs

VolumeC =

Pressure


Measurement of Gas PressureMeasurement of Gas Pressure Barometric pressureBarometric pressure

Partial pressurePartial pressure Partial pressure of water vaporPartial pressure of water vapor


Measurement of Gas PressureMeasurement of Gas Pressure




Gas TransportGas Transport Four stepsFour steps

Ventilation of the lungsVentilation of the lungs Diffusion of oxygen from the alveoli into the Diffusion of oxygen from the alveoli into the

capillary bloodcapillary blood Perfusion of systemic capillaries with oxygenated Perfusion of systemic capillaries with oxygenated

bloodblood Diffusion of oxygen from systemic capillaries into Diffusion of oxygen from systemic capillaries into

the cellsthe cells Diffusion of CODiffusion of CO22 occurs in reverse order occurs in reverse order


Gas TransportGas Transport Distribution of ventilation and perfusionDistribution of ventilation and perfusion

Gravity and alveolar pressureGravity and alveolar pressure Ventilation-perfusion ratioVentilation-perfusion ratio


Gas Transport: OGas Transport: O22

Oxygen transportOxygen transport Diffusion across alveolocapillary membraneDiffusion across alveolocapillary membrane Determinants of arterial oxygenationDeterminants of arterial oxygenation Oxyhemoglobin association and dissociationOxyhemoglobin association and dissociation

• Oxyhemoglobin dissociation curveOxyhemoglobin dissociation curve


Gas Transport: COGas Transport: CO22

Carbon dioxide transportCarbon dioxide transport Dissolved in plasmaDissolved in plasma BicarbonateBicarbonate Carbamino compoundsCarbamino compounds

Haldane effectHaldane effect






Clinical Manifestations: HypoxemiaClinical Manifestations: Hypoxemia EarlyEarly

TachycardiaTachycardia Mild increase in blood pressureMild increase in blood pressure Diaphoresis (stress response)Diaphoresis (stress response) Confusion (CNS response)Confusion (CNS response) Loss of judgmentLoss of judgment Cyanosis after 5 g desaturationCyanosis after 5 g desaturation

LateLate StuporStupor Decreased BP, myocardium not getting enough ODecreased BP, myocardium not getting enough O22


Control of Pulmonary CirculationControl of Pulmonary Circulation Hypoxic vasoconstrictionHypoxic vasoconstriction

Caused by low alveolar POCaused by low alveolar PO22

Blood is shunted to other, well-ventilated portions Blood is shunted to other, well-ventilated portions of the lungsof the lungs• Better ventilation and perfusion matchingBetter ventilation and perfusion matching• If hypoxia affects all segments of lungs, the If hypoxia affects all segments of lungs, the

vasoconstriction can result in pulmonary hypertensionvasoconstriction can result in pulmonary hypertension

Acidemia also causes pulmonary artery Acidemia also causes pulmonary artery constrictionconstriction


Tests of Pulmonary FunctionTests of Pulmonary Function SpirometrySpirometry Diffusion capacityDiffusion capacity Residual volumeResidual volume Functional reserve capacity (FRC)Functional reserve capacity (FRC) Total lung capacityTotal lung capacity Arterial blood gas analysisArterial blood gas analysis Chest radiographsChest radiographs


Aging and the Pulmonary SystemAging and the Pulmonary System Loss of elastic recoilLoss of elastic recoil Stiffening of the chest wallStiffening of the chest wall Alterations in gas exchangeAlterations in gas exchange Increases in flow resistanceIncreases in flow resistance


Aging and the Pulmonary SystemAging and the Pulmonary System

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Structure and Function of the Pulmonary System Chapter 32 Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc