Respiratory SystemRespiratory System
Consists of the respiratory and conducting Consists of the respiratory and conducting zoneszones
Respiratory zone:Respiratory zone: Site of gas exchange Site of gas exchange Consists of bronchioles, alveolar ducts, and alveoliConsists of bronchioles, alveolar ducts, and alveoli
Respiratory SystemRespiratory System
Conducting zone: Conducting zone: Conduits for air to reach the sites of gas exchangeConduits for air to reach the sites of gas exchange Includes all other respiratory structures (e.g., nose, Includes all other respiratory structures (e.g., nose,
nasal cavity, pharynx, trachea)nasal cavity, pharynx, trachea) Respiratory muscles – diaphragm and other Respiratory muscles – diaphragm and other
muscles that promote ventilationmuscles that promote ventilation
Respiratory SystemRespiratory System
Figure 22.1
Major Functions of the Major Functions of the Respiratory SystemRespiratory System
To supply the body with oxygen and dispose To supply the body with oxygen and dispose of carbon dioxideof carbon dioxide
Respiration – four distinct processes must Respiration – four distinct processes must happenhappen Pulmonary ventilation – moving air into and out of Pulmonary ventilation – moving air into and out of
the lungsthe lungs External respiration – gas exchange between the External respiration – gas exchange between the
lungs and the bloodlungs and the blood
Major Functions of the Major Functions of the Respiratory SystemRespiratory System
Transport – transport of oxygen and carbon Transport – transport of oxygen and carbon dioxide between the lungs and tissuesdioxide between the lungs and tissues
Internal respiration – gas exchange between Internal respiration – gas exchange between systemic blood vessels and tissuessystemic blood vessels and tissues
Function of the NoseFunction of the Nose
The only externally visible part of the The only externally visible part of the respiratory system that functions by:respiratory system that functions by: Providing an airway for respirationProviding an airway for respiration Moistening and warming the entering airMoistening and warming the entering air Filtering inspired air and cleaning it of foreign Filtering inspired air and cleaning it of foreign
mattermatter Serving as a resonating chamber for speechServing as a resonating chamber for speech Housing the olfactory receptorsHousing the olfactory receptors
Structure of the NoseStructure of the Nose
Nose is divided into two regions:Nose is divided into two regions: External nose, including the root, bridge, dorsum External nose, including the root, bridge, dorsum
nasi, and apex nasi, and apex Internal nasal cavityInternal nasal cavity
Nasal CavityNasal Cavity
Lies in and posterior to the external noseLies in and posterior to the external nose Is divided by a midline nasal septumIs divided by a midline nasal septum Opens posteriorly into the nasal pharynx via Opens posteriorly into the nasal pharynx via
internal naresinternal nares The ethmoid and sphenoid bones form the roofThe ethmoid and sphenoid bones form the roof The floor is formed by the hard and soft The floor is formed by the hard and soft
palatespalates
Nasal CavityNasal Cavity
Vestibule – nasal cavity superior to the nares Vestibule – nasal cavity superior to the nares Vibrissae – hairs that filter coarse particles from Vibrissae – hairs that filter coarse particles from
inspired airinspired air Olfactory mucosaOlfactory mucosa
Lines the superior nasal cavity Lines the superior nasal cavity Contains smell receptorsContains smell receptors
Nasal CavityNasal Cavity
Respiratory mucosa Respiratory mucosa Lines the balance of the nasal cavity Lines the balance of the nasal cavity Glands secrete mucus containing lysozyme and Glands secrete mucus containing lysozyme and
defensins to help destroy bacteriadefensins to help destroy bacteria
Nasal CavityNasal Cavity
Inspired air is: Inspired air is: Humidified by the high water content in the nasal Humidified by the high water content in the nasal
cavitycavity Warmed by rich plexuses of capillariesWarmed by rich plexuses of capillaries
Ciliated mucosal cells remove contaminated Ciliated mucosal cells remove contaminated mucus mucus
Nasal CavityNasal Cavity
Superior, medial, and inferior conchae:Superior, medial, and inferior conchae: Protrude medially from the lateral wallsProtrude medially from the lateral walls Increase mucosal areaIncrease mucosal area Enhance air turbulence and help filter airEnhance air turbulence and help filter air
Sensitive mucosa triggers sneezing when Sensitive mucosa triggers sneezing when stimulated by irritating particlesstimulated by irritating particles
Functions of the Nasal Mucosa Functions of the Nasal Mucosa and Conchaeand Conchae
During inhalation the conchae and nasal During inhalation the conchae and nasal mucosa:mucosa: Filter, heat, and moisten airFilter, heat, and moisten air
During exhalation these structures:During exhalation these structures: Reclaim heat and moistureReclaim heat and moisture Minimize heat and moisture lossMinimize heat and moisture loss
Paranasal SinusesParanasal Sinuses
Sinuses in bones that surround the nasal cavitySinuses in bones that surround the nasal cavity Sinuses lighten the skull and help to warm and Sinuses lighten the skull and help to warm and
moisten the airmoisten the air
PharynxPharynx
Funnel-shaped tube of skeletal muscle that Funnel-shaped tube of skeletal muscle that connects to the:connects to the: Nasal cavity and mouth superiorlyNasal cavity and mouth superiorly Larynx and esophagus inferiorlyLarynx and esophagus inferiorly
Extends from the base of the skull to the level Extends from the base of the skull to the level of the sixth cervical vertebraof the sixth cervical vertebra
PharynxPharynx
It is divided into three regionsIt is divided into three regions Nasopharynx: posterior to the nasal cavity; air Nasopharynx: posterior to the nasal cavity; air
passageway; lined with pseudostratified columnar passageway; lined with pseudostratified columnar epithelium; auditory tubes open into epithelium; auditory tubes open into
Oropharynx: extends from the soft palate to the Oropharynx: extends from the soft palate to the epiglottis; opens to the oral cavity; common epiglottis; opens to the oral cavity; common passageway for food and air; stratified squamous passageway for food and air; stratified squamous epithelium linesepithelium lines
Laryngopharynx: common passageway for food Laryngopharynx: common passageway for food and air; posterior to the epiglottis; extends to the and air; posterior to the epiglottis; extends to the larynxlarynx
Larynx (Voice Box)Larynx (Voice Box)
Attaches to the hyoid bone and opens into the Attaches to the hyoid bone and opens into the laryngopharynx superiorlylaryngopharynx superiorly
Continuous with the trachea posteriorlyContinuous with the trachea posteriorly The three functions of the larynx are:The three functions of the larynx are:
To provide a patent airwayTo provide a patent airway To act as a switching mechanism to route air and To act as a switching mechanism to route air and
food into the proper channelsfood into the proper channels To function in voice productionTo function in voice production
Framework of the LarynxFramework of the Larynx
Cartilages (hyaline) of the larynxCartilages (hyaline) of the larynx Shield-shaped thyroid cartilage with a midline Shield-shaped thyroid cartilage with a midline
laryngeal prominence (Adam’s apple)laryngeal prominence (Adam’s apple) Signet ring–shaped cricoid cartilageSignet ring–shaped cricoid cartilage Three pairs of small arytenoid, cuneiform, and Three pairs of small arytenoid, cuneiform, and
corniculate cartilagescorniculate cartilages Epiglottis – elastic cartilage that covers the Epiglottis – elastic cartilage that covers the
laryngeal inlet during swallowinglaryngeal inlet during swallowing
Framework of the LarynxFramework of the Larynx
Figure 22.4a, b
Vocal LigamentsVocal Ligaments
Attach the arytenoid cartilages to the thyroid Attach the arytenoid cartilages to the thyroid cartilagecartilage
Composed of elastic fibers that form mucosal Composed of elastic fibers that form mucosal folds called true vocal cordsfolds called true vocal cords The medial opening between them is the glottisThe medial opening between them is the glottis They vibrate to produce sound as air rushes up They vibrate to produce sound as air rushes up
from the lungsfrom the lungs
Vocal LigamentsVocal Ligaments
False vocal cordsFalse vocal cords Mucosal folds superior to the true vocal cordsMucosal folds superior to the true vocal cords Have no part in sound productionHave no part in sound production
Vocal ProductionVocal Production Speech – intermittent release of expired air Speech – intermittent release of expired air
while opening and closing the glottiswhile opening and closing the glottis Pitch – determined by the length and tension of Pitch – determined by the length and tension of
the vocal cords the vocal cords Loudness – depends upon the force at which Loudness – depends upon the force at which
the air rushes across the vocal cordsthe air rushes across the vocal cords The pharynx resonates, amplifies, and The pharynx resonates, amplifies, and
enhances sound qualityenhances sound quality Sound is “shaped” into language by action of Sound is “shaped” into language by action of
the pharynx, tongue, soft palate, and lipsthe pharynx, tongue, soft palate, and lips
Movements of Vocal CordsMovements of Vocal Cords
Figure 22.5
Sphincter Functions of the Sphincter Functions of the LarynxLarynx
The larynx is closed during coughing, sneezing, The larynx is closed during coughing, sneezing, and Valsalva’s maneuver and Valsalva’s maneuver
Valsalva’s maneuverValsalva’s maneuver Air is temporarily held in the lower respiratory tract Air is temporarily held in the lower respiratory tract
by closing the glottis by closing the glottis Causes intra-abdominal pressure to rise when Causes intra-abdominal pressure to rise when
abdominal muscles contractabdominal muscles contract Helps to empty the rectumHelps to empty the rectum Acts as a splint to stabilize the trunk when lifting Acts as a splint to stabilize the trunk when lifting
heavy loadsheavy loads
TracheaTrachea
Flexible and mobile tube extending from the Flexible and mobile tube extending from the larynx into the mediastinumlarynx into the mediastinum
Composed of three layersComposed of three layers Mucosa – made up of goblet cells and ciliated Mucosa – made up of goblet cells and ciliated
epithelium epithelium Submucosa – connective tissue deep to the mucosaSubmucosa – connective tissue deep to the mucosa Adventitia – outermost layer made of C-shaped Adventitia – outermost layer made of C-shaped
rings of hyaline cartilagerings of hyaline cartilage
Conducting Zone: BronchiConducting Zone: Bronchi
Last tracheal cartilage marks the end of the Last tracheal cartilage marks the end of the trachea and the beginning of the bronchitrachea and the beginning of the bronchi
Air reaching the bronchi is:Air reaching the bronchi is: Warm and cleansed of impuritiesWarm and cleansed of impurities Saturated with water vaporSaturated with water vapor
Bronchi subdivide into secondary bronchi, Bronchi subdivide into secondary bronchi, each supplying a lobe of the lungseach supplying a lobe of the lungs
Air passages undergo 23 orders of branchingAir passages undergo 23 orders of branching
Conducting Zone: Bronchial Conducting Zone: Bronchial TreeTree
Tissue walls of bronchi mimic that of the Tissue walls of bronchi mimic that of the tracheatrachea
As conducting tubes become smaller, As conducting tubes become smaller, structural changes occurstructural changes occur Cartilage support structures changeCartilage support structures change Epithelium types changeEpithelium types change Amount of smooth muscle increasesAmount of smooth muscle increases
Conducting Zone: Bronchial Conducting Zone: Bronchial TreeTree
Bronchioles Bronchioles Consist of cuboidal epitheliumConsist of cuboidal epithelium Have a complete layer of circular smooth muscle Have a complete layer of circular smooth muscle Lack cartilage support and mucus-producing cellsLack cartilage support and mucus-producing cells
Conducting ZonesConducting Zones
Figure 22.7
Respiratory ZoneRespiratory Zone
Defined by the presence of alveoli; begins as Defined by the presence of alveoli; begins as terminal bronchioles feed into respiratory terminal bronchioles feed into respiratory bronchiolesbronchioles
Respiratory bronchioles lead to alveolar ducts, Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs then to terminal clusters of alveolar sacs composed of alveolicomposed of alveoli
Approximately 300 million alveoli:Approximately 300 million alveoli: Account for most of the lungs’ volume Account for most of the lungs’ volume Provide tremendous surface area for gas exchangeProvide tremendous surface area for gas exchange
Respiratory ZoneRespiratory Zone
Figure 22.8a
Respiratory ZoneRespiratory Zone
Figure 22.8b
Respiratory MembraneRespiratory Membrane
This air-blood barrier is composed of: This air-blood barrier is composed of: Alveolar and capillary wallsAlveolar and capillary walls Their fused basal laminasTheir fused basal laminas
Alveolar walls:Alveolar walls: Are a single layer of type I epithelial cellsAre a single layer of type I epithelial cells Permit gas exchange by simple diffusionPermit gas exchange by simple diffusion Secrete angiotensin converting enzyme (ACE)Secrete angiotensin converting enzyme (ACE)
Type II cells secrete surfactantType II cells secrete surfactant
AlveoliAlveoli
Surrounded by fine elastic fibersSurrounded by fine elastic fibers Contain open pores that:Contain open pores that:
Connect adjacent alveoliConnect adjacent alveoli Allow air pressure throughout the lung to be Allow air pressure throughout the lung to be
equalizedequalized House macrophages that keep alveolar House macrophages that keep alveolar
surfaces sterilesurfaces sterile
Gross Anatomy of the LungsGross Anatomy of the Lungs
Lungs occupy all of the thoracic cavity except Lungs occupy all of the thoracic cavity except the mediastinumthe mediastinum Root – site of vascular and bronchial attachmentsRoot – site of vascular and bronchial attachments Costal surface – anterior, lateral, and posterior Costal surface – anterior, lateral, and posterior
surfaces in contact with the ribssurfaces in contact with the ribs Apex – narrow superior tipApex – narrow superior tip Base – inferior surface that rests on the diaphragmBase – inferior surface that rests on the diaphragm Hilus – indentation that contains pulmonary and Hilus – indentation that contains pulmonary and
systemic blood vesselssystemic blood vessels
Organs in the Thoracic CavityOrgans in the Thoracic Cavity
Figure 22.10a
Transverse Thoracic SectionTransverse Thoracic Section
Figure 22.10c
LungsLungs
Cardiac notch (impression) – cavity that Cardiac notch (impression) – cavity that accommodates the heartaccommodates the heart
Left lung – separated into upper and lower Left lung – separated into upper and lower lobes by the oblique fissurelobes by the oblique fissure
Right lung – separated into three lobes by the Right lung – separated into three lobes by the oblique and horizontal fissuresoblique and horizontal fissures
There are 10 bronchopulmonary segments in There are 10 bronchopulmonary segments in each lungeach lung
Blood Supply to LungsBlood Supply to Lungs
Lungs are perfused by two circulations: Lungs are perfused by two circulations: pulmonary and bronchialpulmonary and bronchial
Pulmonary arteries – supply systemic venous Pulmonary arteries – supply systemic venous blood to be oxygenatedblood to be oxygenated Branch profusely, along with bronchiBranch profusely, along with bronchi Ultimately feed into the pulmonary capillary Ultimately feed into the pulmonary capillary
network surrounding the alveolinetwork surrounding the alveoli Pulmonary veins – carry oxygenated blood Pulmonary veins – carry oxygenated blood
from respiratory zones to the heartfrom respiratory zones to the heart
Blood Supply to LungsBlood Supply to Lungs
Bronchial arteries – provide systemic blood to Bronchial arteries – provide systemic blood to the lung tissuethe lung tissue Arise from aorta and enter the lungs at the hilusArise from aorta and enter the lungs at the hilus Supply all lung tissue except the alveoliSupply all lung tissue except the alveoli
Bronchial veins anastomose with pulmonary Bronchial veins anastomose with pulmonary veinsveins
Pulmonary veins carry most venous blood Pulmonary veins carry most venous blood back to the heartback to the heart
PleuraePleurae
Thin, double-layered serosa Thin, double-layered serosa Parietal pleuraParietal pleura
Covers the thoracic wall and superior face of the Covers the thoracic wall and superior face of the diaphragmdiaphragm
Continues around heart and between lungsContinues around heart and between lungs
PleuraePleurae
Visceral, or pulmonary, pleuraVisceral, or pulmonary, pleura Covers the external lung surfaceCovers the external lung surface Divides the thoracic cavity into three chambersDivides the thoracic cavity into three chambers
The central mediastinumThe central mediastinum Two lateral compartments, each containing a lung Two lateral compartments, each containing a lung
BreathingBreathing
Breathing, or pulmonary ventilation, consists Breathing, or pulmonary ventilation, consists of two phasesof two phases Inspiration – air flows into the lungsInspiration – air flows into the lungs Expiration – gases exit the lungsExpiration – gases exit the lungs
Pressure Relationships in the Pressure Relationships in the Thoracic CavityThoracic Cavity
Respiratory pressure is always described Respiratory pressure is always described relative to atmospheric pressurerelative to atmospheric pressure
Atmospheric pressure (PAtmospheric pressure (Patmatm)) Pressure exerted by the air surrounding the body Pressure exerted by the air surrounding the body Negative respiratory pressure is less than PNegative respiratory pressure is less than Patmatm
Positive respiratory pressure is greater than PPositive respiratory pressure is greater than Patmatm
Pressure Relationships in the Pressure Relationships in the Thoracic CavityThoracic Cavity
Intrapulmonary pressure (PIntrapulmonary pressure (Ppulpul) – pressure ) – pressure
within the alveoliwithin the alveoli Intrapleural pressure (PIntrapleural pressure (Pipip) – pressure within the ) – pressure within the
pleural cavitypleural cavity
Pressure RelationshipsPressure Relationships
Intrapulmonary pressure and intrapleural Intrapulmonary pressure and intrapleural pressure fluctuate with the phases of breathingpressure fluctuate with the phases of breathing
Intrapulmonary pressure always eventually Intrapulmonary pressure always eventually equalizes itself with atmospheric pressureequalizes itself with atmospheric pressure
Intrapleural pressure is always less than Intrapleural pressure is always less than intrapulmonary pressure and atmospheric intrapulmonary pressure and atmospheric pressurepressure
Pressure RelationshipsPressure Relationships
Two forces act to pull the lungs away from the Two forces act to pull the lungs away from the thoracic wall, promoting lung collapsethoracic wall, promoting lung collapse Elasticity of lungs causes them to assume smallest Elasticity of lungs causes them to assume smallest
possible sizepossible size Surface tension of alveolar fluid draws alveoli to Surface tension of alveolar fluid draws alveoli to
their smallest possible sizetheir smallest possible size Opposing force – elasticity of the chest wall Opposing force – elasticity of the chest wall
pulls the thorax outward to enlarge the lungspulls the thorax outward to enlarge the lungs
Pressure RelationshipsPressure Relationships
Figure 22.12
Lung CollapseLung Collapse
Caused by equalization of the intrapleural Caused by equalization of the intrapleural pressure with the intrapulmonary pressurepressure with the intrapulmonary pressure
Transpulmonary pressure keeps the airways Transpulmonary pressure keeps the airways openopen
Pulmonary VentilationPulmonary Ventilation
A mechanical process that depends on volume A mechanical process that depends on volume changes in the thoracic cavitychanges in the thoracic cavity
Volume changes lead to pressure changes, Volume changes lead to pressure changes, which lead to the flow of gases to equalize which lead to the flow of gases to equalize pressurepressure
Boyle’s LawBoyle’s Law
Boyle’s law – the relationship between the Boyle’s law – the relationship between the pressure and volume of gases pressure and volume of gases
PP11VV11 = P = P22VV22
P = pressure of a gas in mm HgP = pressure of a gas in mm Hg V = volume of a gas in cubic millimetersV = volume of a gas in cubic millimeters Subscripts 1 and 2 represent the initial and Subscripts 1 and 2 represent the initial and
resulting conditions, respectivelyresulting conditions, respectively
InspirationInspiration
The diaphragm and external intercostal muscles The diaphragm and external intercostal muscles (inspiratory muscles) contract and the rib cage (inspiratory muscles) contract and the rib cage risesrises
The lungs are stretched and intrapulmonary The lungs are stretched and intrapulmonary volume increasesvolume increases
Intrapulmonary pressure drops below Intrapulmonary pressure drops below atmospheric pressure (atmospheric pressure (1 mm Hg)1 mm Hg)
Air flows into the lungs, down its pressure Air flows into the lungs, down its pressure gradient, until intrapleural pressure = gradient, until intrapleural pressure = atmospheric pressureatmospheric pressure
ExpirationExpiration
Inspiratory muscles relax and the rib cage Inspiratory muscles relax and the rib cage descends due to gravitydescends due to gravity
Thoracic cavity volume decreasesThoracic cavity volume decreases Elastic lungs recoil passively and Elastic lungs recoil passively and
intrapulmonary volume decreasesintrapulmonary volume decreases Intrapulmonary pressure rises above Intrapulmonary pressure rises above
atmospheric pressure (+1 mm Hg)atmospheric pressure (+1 mm Hg) Gases flow out of the lungs down the pressure Gases flow out of the lungs down the pressure
gradient until intrapulmonary pressure is 0gradient until intrapulmonary pressure is 0
Friction is the major nonelastic source of Friction is the major nonelastic source of resistance to airflowresistance to airflow
Physical Factors Influencing Physical Factors Influencing Ventilation: Ventilation:
Airway ResistanceAirway Resistance
The amount of gas flowing into and out of the The amount of gas flowing into and out of the alveoli is directly proportional to alveoli is directly proportional to P, the P, the pressure gradient between the atmosphere and pressure gradient between the atmosphere and the alveolithe alveoli
Gas flow is inversely proportional to resistance Gas flow is inversely proportional to resistance with the greatest resistance being in the with the greatest resistance being in the medium-sized bronchimedium-sized bronchi
Physical Factors Influencing Physical Factors Influencing Ventilation: Ventilation:
Airway ResistanceAirway Resistance
Airway ResistanceAirway Resistance
As airway resistance rises, breathing As airway resistance rises, breathing movements become more strenuousmovements become more strenuous
Severely constricted or obstructed bronchioles: Severely constricted or obstructed bronchioles: Can prevent life-sustaining ventilationCan prevent life-sustaining ventilation Can occur during acute asthma attacks which stops Can occur during acute asthma attacks which stops
ventilationventilation Epinephrine release via the sympathetic Epinephrine release via the sympathetic
nervous system dilates bronchioles and nervous system dilates bronchioles and reduces air resistancereduces air resistance
Alveolar Surface TensionAlveolar Surface Tension
Surface tension – the attraction of liquid Surface tension – the attraction of liquid molecules to one another at a liquid-gas molecules to one another at a liquid-gas interface interface
The liquid coating the alveolar surface is The liquid coating the alveolar surface is always acting to reduce the alveoli to the always acting to reduce the alveoli to the smallest possible sizesmallest possible size
Surfactant, a detergent-like complex, reduces Surfactant, a detergent-like complex, reduces surface tension and helps keep the alveoli from surface tension and helps keep the alveoli from collapsingcollapsing
Lung ComplianceLung Compliance
The ease with which lungs can be expandedThe ease with which lungs can be expanded Specifically, the measure of the change in lung Specifically, the measure of the change in lung
volume that occurs with a given change in volume that occurs with a given change in transpulmonary pressuretranspulmonary pressure
Determined by two main factorsDetermined by two main factors Distensibility of the lung tissue and surrounding Distensibility of the lung tissue and surrounding
thoracic cagethoracic cage Surface tension of the alveoliSurface tension of the alveoli
Factors That Diminish Lung Factors That Diminish Lung ComplianceCompliance
Scar tissue or fibrosis that reduces the natural Scar tissue or fibrosis that reduces the natural resilience of the lungsresilience of the lungs
Blockage of the smaller respiratory passages Blockage of the smaller respiratory passages with mucus or fluidwith mucus or fluid
Reduced production of surfactantReduced production of surfactant Decreased flexibility of the thoracic cage or its Decreased flexibility of the thoracic cage or its
decreased ability to expanddecreased ability to expand
Factors That Diminish Lung Factors That Diminish Lung ComplianceCompliance
Examples include: Examples include: Deformities of thoraxDeformities of thorax Ossification of the costal cartilageOssification of the costal cartilage Paralysis of intercostal musclesParalysis of intercostal muscles
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