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The Respiratory The Respiratory SystemSystem

The Respiratory The Respiratory SystemSystem

Chapter 18

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Helps pH control

OperationsOperationsOperationsOperations

• Pulmonary ventilationMoving air in & out

• External respirationGas exchange between alveoli &

blood

• Internal respirationGas exchange between blood & cells

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Anatomical Anatomical ComponentsComponentsAnatomical Anatomical

ComponentsComponents

• Upper respiratory tractnose, pharynx

• Lower Respiratory SystemTrachea, larynx & bronchi & lungs

•Conducting zone = tubing•Respiratory Zone= Gas

exchangeBronchioles, alveolar sacs & alveoli

Figure 18.1Figure 18.1

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NoseNoseNoseNose

• Nose: external nares nasal cavity internal naresNasal septum splits in twoNasal conchae swirl air over mucus

membrane

• Designed to: Filter, Warm, Humidify• Trap dust and infectious agents• Detect olfactory stimuli• Modify vocal sounds

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PharynxPharynxPharynxPharynx

• Funnel shaped tube from internal nares to larynx = “throat”

• Upper = naso pharynx• Middle = oropharynx

Between uvula & top of epiglottis• lower = laryngeal pharynx

Connects with both esophagus & larynx

Thus both air & food & drink

Figure 18.2Figure 18.2

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LarynxLarynxLarynxLarynx

• Short tube of cartilage• Thyroid cartilage-

anterior = “Adam's apple”• Epiglottis – upper leaf-shaped piece

During swallowing larynx moves up and epiglottis covers opening to trachea

• Cricoid cartilage- forms inferior wall• Paired arytenoids- above cricoid

attach to vocal cords & pharyngeal muscles

Figure 18.3Figure 18.3

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Voice ProductionVoice ProductionVoice ProductionVoice Production

• Mucous membrane of larynx two pairs of folds

• Upper = false vocal cords• Lower = true vocal cords

Contain elastic ligaments stretched between cartilage

Move out into air way and vibratePitch adjusted by tension and diameter of

ligaments

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TracheaTracheaTracheaTrachea

• Trachea- larynx upper part of T5 vertebra R. & L. primary bronchusLined with pseudostratified ciliated

mucous membrane dust protection – move toward

pharynx

• C-shaped cartilage rings keep lumen open

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Bronchi & BronchiolesBronchi & BronchiolesBronchi & BronchiolesBronchi & Bronchioles

• Bronchi also contain cartilage rings• Primary bronchi enter the lungs

Blood vessels, lymphatic vessels & nerves enter lungs with bronchi

• In lungs branch secondary bronchione for each lobe of lung

tertiary bronchi terminal bronchi

• Smaller bronchi have less cartilage and more smooth muscleANS can adjust diameter = resistance to flow

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LungsLungsLungsLungs

• Two organs (R. & L)• Surrounded by pleural membrane

Parietal pleura attached to diaphragm & thoracic wall

Visceral pleura attached to lungsBetween is pleural cavity filled with fluidBroad bottom = base; Pointy top = apex

• Right lung has 3 lobes• Left lung has 3 lobes & cardiac notch

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Lung LobesLung LobesLung LobesLung Lobes

• Divided in lobules fed by tertiary bronchus

• Further divisions terminal bronchiole

respiratory bronchioleLined with non-ciliated cuboidal

epithelium

alveolar ducts alveolar sacs

FigureFigure 18.4FigureFigure 18.4

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AlveoliAlveoliAlveoliAlveoli

• Cup-shaped out pouch of sacLined with thin alveolar cells (simple

squamous)

• Scattered surfactant secreting cellsLowers surface tension & humidifies

• Alveolar macrophages- “cleaners”• Gases diffuse across combined epithelia

of alveolus & capillary• Combination called: Respiratory

Membrane

Figure 18.5Figure 18.5

Figure 18.6Figure 18.6

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Pulmonary VentilationPulmonary VentilationPulmonary VentilationPulmonary Ventilation

• Air flows between atmosphere & lungs due to difference in pressureCaused by respiratory muscles

• Inhalation: diaphragm & external intercostalsDiaphragm contracts lung volume

• Lung moves due to seal between parietal & visceral plura

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ExhalationExhalationExhalationExhalation

• Resting exhalation due to muscle relaxation= passive processDiaphragm rises & ribs fall lung

volume

• Can be active using internal intercostals & abdominal musclesPush diaphragm up & pull ribs in More lung volume

Figure 18.7aFigure 18.7a

Figure 18.7bFigure 18.7b

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Pressure ChangesPressure ChangesPressure ChangesPressure Changes

lung volume alveolar pressure

• Atmospheric pressure is constant • Atmospheric > alveolar

inhalation• During exhalation lung rises • Alveolar> Atmospheric

exhalation

Figure 18.8Figure 18.8

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Air Flow TermsAir Flow TermsAir Flow TermsAir Flow Terms

• Frequency (f) = breaths per minuteNormal ~12 breaths per min

• Tidal volume (TV) = volume moved in one breathNormal ~ 500 ml

• Minute Ventilation (MV) = f x TV• ~ 70% of TV reaches alveoli (350 ml)

Only this involved in gas exchange

• 30% in airways = Anatomic Dead Space

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Lung VolumesLung VolumesLung VolumesLung Volumes

• Inspiration beyond resting = Inspiratory reserve volume

• Expiration beyond resting (active) = Expiratory reserve volume

• Air left after a maximum expiration = residual volume

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Lung CapacitiesLung CapacitiesLung CapacitiesLung Capacities

• Inspiratory capacity= TV + inspiratory reserve

•Functional residual capacity =Residual volume + expiratory reserve

•Vital capacity (VC) = Expiratory reserve + TV + Inspiratory

reserve• Total lung capacity = VC + residual

Figure 18.9Figure 18.9

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Breathing PatternsBreathing PatternsBreathing PatternsBreathing Patterns

• Eupnea = normal breathingHighly variable in pattern

• Special modifications for speech and emotional responses

• Also variations fro coughing & sneezing to clear airwaysSee table 18.1

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Nature of AirNature of AirNature of AirNature of Air

• Mixture of gases (N2, O2,, CO2, H2O & others)

• Each gas has own partial pressure (Px)

• Each gas diffuses down partial pressure gradient

• Total = sum of partial pressures = atmospheric pressure

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Pulmonary Gas Pulmonary Gas Exchange: External Exchange: External

RespirationRespiration

Pulmonary Gas Pulmonary Gas Exchange: External Exchange: External

RespirationRespiration

• O2 diffuses from air (PO2 ~105mm Hg) incoming blood (PO2 ~40mm Hg)

• Continues until equilibrium (PO2 ~105mm Hg) Some unexchanged mixture in out flow so

Arterial blood is ~100 mmHg

• Meanwhile blood (PCO2 ~45) diffuses to alveolar air (PCO2 ~40) Again to equilibrium

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Systemic Gas Exchange: Systemic Gas Exchange: Internal RespirationInternal Respiration

Systemic Gas Exchange: Systemic Gas Exchange: Internal RespirationInternal Respiration

• Occurs throughout body

• O2 diffuses from blood to cells

• PO2 lower in cells because of use

• Meanwhile CO2 diffuses in opposite direction

Figure 18.10Figure 18.10

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Transport of OxygenTransport of OxygenTransport of OxygenTransport of Oxygen

• O2 dissolves poorly 98.5% bound to hemoglobin in RBCsBinding depends on PO2

High at lung and lower at tissue PO2s

• Tissue release of O2 increased by:High CO2 AcidityHigher temperatures

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Transport of Carbon Transport of Carbon DioxideDioxide

Transport of Carbon Transport of Carbon DioxideDioxide

• As comes in to blood from cells• Some dissolved (7%)• Bound to proteins including

Hemoglobin (23%)• Becomes bicarbonate ions (70%)

CO2 + H2O <=> H+ + HCO3-

• Process reverses at lungs

Figure 18.11Figure 18.11

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Control of RespirationControl of RespirationControl of RespirationControl of Respiration

• Medullary respiratory area in medullaContains both inspiratory & expiratory areas

• Quiet breathing: inspiratory area nerve signals to inspiratory

muscles for ~2 secinspirationThen becomes inactive & muscles relaxExpirationExpiratory centre active only during forceful

breathing

• Area in pons adjusts length of inspiratory stimulation

Figure 18.12aFigure 18.12a

Figure 18.12bFigure 18.12b

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Regulation of Respiratory Regulation of Respiratory CenterCenter

Regulation of Respiratory Regulation of Respiratory CenterCenter

• Cortical input: voluntary adjustment of patternsProtection & talkingChemoreceptor input will override breath-hold

• Chemoreceptor inputCentral receptors in medullaPeripheral receptors in arch of aorta

respond to increased H+ or PCO2 increased ventilation

• Thus negative feedback loop to maintain blood & brain pH

• Significant falls in PO2 also stimulates breathing

Figure 18.13Figure 18.13

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Other Regulatory Other Regulatory FactorsFactors

Other Regulatory Other Regulatory FactorsFactors

• Limbic system- anticipation of activity or emotion can

stimulate• Proprioception stimulates on start

of activity• Temperature warming increases• Pain- Sudden pain apnea

Prolonged somatic pain can increase rate• Airway irritation cough or sneeze• Inflation reflex- bronchi wall stretch

receptors inhibit inspirationPrevents overinflation

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AgingAgingAgingAging

• Everything becomes less elastic

• Decrease in Vital capacity

• Can decrease blood O2 level

• Decreased exercise capacity• Decreased macrophage activity• Increased susceptibility to

pulmonary disease