bio 122 chapter 22
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Chapter 22, Respiratory System 1
22
The Respiratory System
Anatomy
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Chapter 22, Respiratory System 2
Respiratory System
Consists of the respiratory and conducting zones
Respiratory zone
Site of gas exchange
Consists of bronchioles, alveolar ducts, and alveoli
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Chapter 22, Respiratory System 3
Respiratory System
Conducting zone
Provides rigid conduits for air to reach the sites of
gas exchange
Includes all other respiratory structures (e.g., nose,nasal cavity, pharynx, trachea)
Respiratory musclesdiaphragm and other musclesthat promote ventilation
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Chapter 22, Respiratory System 4
Respiratory System
Figure 22.1
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Chapter 22, Respiratory System 5
Major Functions of the Respiratory System
To supply the body with oxygen and dispose of
carbon dioxide
Respirationfour distinct processes must happen
Pulmonary ventilationmoving air into and out of
the lungs
External respirationgas exchange between the
lungs and the blood
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Chapter 22, Respiratory System 6
Major Functions of the Respiratory System
Transporttransport of oxygen and carbon dioxide
between the lungs and tissues
Internal respirationgas exchange between
systemic blood vessels and tissues
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Chapter 22, Respiratory System 7
Function of the Nose
The only externally visible part of the respiratory
system that functions by:
Providing an airway for respiration
Moistening (humidifying) and warming theentering air
Filtering inspired air and cleaning it of foreign
matter
Serving as a resonating chamber for speech
Housing the olfactory receptors
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Chapter 22, Respiratory System 8
Structure of the Nose
The nose is divided into two regions
The external nose, including the root, bridge,
dorsum nasi, and apex
The internal nasal cavity
Philtruma shallow vertical groove inferior to the
apex The external nares (nostrils) are bounded laterally
by the alae
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Chapter 22, Respiratory System 9
Structure of the Nose
Figure 22.2a
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Chapter 22, Respiratory System 10
Structure of the Nose
Figure 22.2b
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Chapter 22, Respiratory System 11
Nasal Cavity
Lies in and posterior to the external nose
Is divided by a midline nasal septum
Opens posteriorly into the nasal pharynx via internal
nares
The ethmoid and sphenoid bones form the roof
The floor is formed by the hard and soft palates
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Chapter 22, Respiratory System 12
Nasal Cavity
Vestibulenasal cavity superior to the nares
Vibrissaehairs that filter coarse particles from
inspired air
Olfactory mucosa
Lines the superior nasal cavity Contains smell receptors
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Chapter 22, Respiratory System 13
Nasal Cavity
Respiratory mucosa
Lines the balance of the nasal cavity
Glands secrete mucus containing lysozyme and
defensins to help destroy bacteria
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Chapter 22, Respiratory System 14
Nasal Cavity
Figure 22.3b
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Chapter 22, Respiratory System 15
Nasal Cavity
Inspired air is:
Humidified by the high water content in the nasalcavity
Warmed by rich plexuses of capillaries
Ciliated mucosal cells remove contaminated mucus
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Chapter 22, Respiratory System 16
Nasal Cavity
Superior, medial, and inferior conchae:
Protrude medially from the lateral walls
Increase mucosal area
Enhance air turbulence and help filter air
Sensitive mucosa triggers sneezing when stimulatedby irritating particles
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Chapter 22, Respiratory System 17
Functions of the Nasal Mucosa and Conchae
During inhalation the conchae and nasal mucosa:
Filter, heat, and moisten air
During exhalation these structures:
Reclaim heat and moisture
Minimize heat and moisture loss
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Chapter 22, Respiratory System 18
Paranasal Sinuses
Sinuses in bones that surround the nasal cavity
Sinuses lighten the skull and help to warm and
moisten the air
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Chapter 22, Respiratory System 19
Pharynx
Funnel-shaped tube of skeletal muscle that connects
to the:
Nasal cavity and mouth superiorly
Larynx and esophagus inferiorly
Extends from the base of the skull to the level of thesixth cervical vertebra
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Chapter 22, Respiratory System 20
Pharynx
It is divided into three regions
Nasopharynx
Oropharynx
Laryngopharynx
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Chapter 22, Respiratory System 22
Oropharynx
Extends inferiorly from the level of the soft palate to
the epiglottis
Opens to the oral cavity via an archway called the
fauces
Serves as a common passageway for food and air
The epithelial lining is protective stratified
squamous epithelium
Palatine tonsils lie in the lateral walls of the fauces
Lingual tonsil covers the base of the tongue
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Chapter 22, Respiratory System 23
Laryngopharynx
Serves as a common passageway for food and air
Lies posterior to the upright epiglottis
Extends to the larynx, where the respiratory and
digestive pathways diverge
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Chapter 22, Respiratory System 24
Larynx (Voice Box)
Attaches to the hyoid bone and opens into the
laryngopharynx superiorly
Continuous with the trachea posteriorly
The three functions of the larynx are:
To provide a patent airway
To act as a switching mechanism to route air andfood into the proper channels
To function in voice production
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Chapter 22, Respiratory System 25
Framework of the Larynx
Cartilages (hyaline) of the larynx
Shield-shaped anterosuperior thyroid cartilage with
a midline laryngeal prominence (Adams apple)
Signet ringshaped anteroinferior cricoid cartilage
Three pairs of small arytenoid, cuneiform, and
corniculate cartilages
Epiglottiselastic cartilage that covers the
laryngeal inlet during swallowing
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Chapter 22, Respiratory System 26
Framework of the Larynx
Figure 22.4a, b
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Chapter 22, Respiratory System 27
Vocal Ligaments
Attach the arytenoid cartilages to the thyroid
cartilage
Composed of elastic fibers that form mucosal foldscalled true vocal cords
The medial opening between them is the glottis
They vibrate to produce sound as air rushes up from
the lungs
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Chapter 22, Respiratory System 28
Vocal Ligaments
False vocal cords
Mucosal folds superior to the true vocal cords
Have no part in sound production
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Chapter 22, Respiratory System 29
Vocal Production
Speechintermittent release of expired air while
opening and closing the glottis
Pitchdetermined by the length and tension of thevocal cords
Loudnessdepends upon the force at which the airrushes across the vocal cords
The pharynx resonates, amplifies, and enhances
sound quality
Sound is shaped into language by action of thepharynx, tongue, soft palate, and lips
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Chapter 22, Respiratory System 30
Movements of Vocal Cords
Figure 22.5
S i i f
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Chapter 22, Respiratory System 31
Sphincter Functions of the Larynx
The larynx is closed during coughing, sneezing, and
Valsalvas maneuver
Valsalvas maneuver
Air is temporarily held in the lower respiratory tractby closing the glottis
Causes intra-abdominal pressure to rise whenabdominal muscles contract
Helps to empty the rectum
Acts as a splint to stabilize the trunk when liftingheavy loads
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T h
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Chapter 22, Respiratory System 33
Trachea
Figure 22.6a
C d ti Z B hi
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Chapter 22, Respiratory System 34
Conducting Zone: Bronchi
The carina of the last tracheal cartilage marks the
end of the trachea and the beginning of the right andleft bronchi
Air reaching the bronchi is:
Warm and cleansed of impurities
Saturated with water vapor
Bronchi subdivide into secondary bronchi, eachsupplying a lobe of the lungs
Air passages undergo 23 orders of branching in thelungs
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C d ti Z B hi l T
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Chapter 22, Respiratory System 36
Conducting Zone: Bronchial Tree
Bronchioles
Consist of cuboidal epithelium
Have a complete layer of circular smooth muscle
Lack cartilage support and mucus-producing cells
R i t Z
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Chapter 22, Respiratory System 37
Respiratory Zone
Defined by the presence of alveoli; begins as
terminal bronchioles feed into respiratorybronchioles
Respiratory bronchioles lead to alveolar ducts, then
to terminal clusters of alveolar sacs composed ofalveoli
Approximately 300 million alveoli:
Account for most of the lungs volume
Provide tremendous surface area for gas exchange
R i t Z
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Chapter 22, Respiratory System 38
Respiratory Zone
Figure 22.8a
R i t Z
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Chapter 22, Respiratory System 39
Respiratory Zone
Figure 22.8b
R i t M b
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Chapter 22, Respiratory System 40
Respiratory Membrane
This air-blood barrier is composed of:
Alveolar and capillary walls
Their fused basal laminas
Alveolar walls:
Are a single layer of type I epithelial cells
Permit gas exchange by simple diffusion
Secrete angiotensin converting enzyme (ACE)
Type II cells secrete surfactant
Al eoli
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Chapter 22, Respiratory System 41
Alveoli
Surrounded by fine elastic fibers
Contain open pores that:
Connect adjacent alveoli
Allow air pressure throughout the lung to be
equalized
House macrophages that keep alveolar surfacessterile
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Chapter 22, Respiratory System 42
Respiratory Membrane
Figure 22.9b
Respiratory Membrane
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Chapter 22, Respiratory System 43
Respiratory Membrane
Figure 22.9.c, d
Gross Anatomy of the Lungs
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Chapter 22, Respiratory System 44
Gross Anatomy of the Lungs
Lungs occupy all of the thoracic cavity except the
mediastinum
Rootsite of vascular and bronchial attachments
Costal surfaceanterior, lateral, and posteriorsurfaces in contact with the ribs
Apexnarrow superior tip
Baseinferior surface that rests on the diaphragm
Hilusindentation that contains pulmonary and
systemic blood vessels
Lungs
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Chapter 22, Respiratory System 45
Lungs
Cardiac notch (impression)cavity thataccommodates the heart
Left lungseparated into upper and lower lobes by
the oblique fissure
Right lungseparated into three lobes by the
oblique and horizontal fissures
There are 10 bronchopulmonary segments in each
lung
Gross Anatomy of Lungs
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Chapter 22, Respiratory System 46
Gross Anatomy of Lungs
Base, apex (cupula), costal surface, cardiac notch
Oblique & horizontal fissure in right lung results in 3 lobes
Oblique fissure only in left lung produces 2 lobes
Mediastinal Surface of Lungs
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Chapter 22, Respiratory System 47
Mediastinal Surface of Lungs
Blood vessels & airways enter lungs at hilus
Forms root of lungs
Covered with pleura (parietal becomes visceral)
Blood Supply to Lungs
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Chapter 22, Respiratory System 48
Blood Supply to Lungs
Lungs are perfused by two circulations: pulmonary
and bronchial
Pulmonary arteriessupply systemic venous blood
to be oxygenated
Branch profusely, along with bronchi
Ultimately feed into the pulmonary capillary
network surrounding the alveoli
Pulmonary veinscarry oxygenated blood from
respiratory zones to the heart
Blood Supply to Lungs
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Chapter 22, Respiratory System 49
Blood Supply to Lungs
Bronchial arteriesprovide systemic blood to thelung tissue
Arise from aorta and enter the lungs at the hilus
Supply all lung tissue except the alveoli
Bronchial veins anastomose with pulmonary veins
Pulmonary veins carry most venous blood back to
the heart
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Pleurae
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Chapter 22, Respiratory System 51
Pleurae
Visceral, or pulmonary, pleura
Covers the external lung surface
Divides the thoracic cavity into three chambers
The central mediastinum
Two lateral compartments, each containing alung
Breathing
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Chapter 22, Respiratory System 52
Breathing
Breathing, or pulmonary ventilation, consists of two
phases
Inspirationair flows into the lungs
Expirationgases exit the lungs
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Pressure Relationships in the Thoracic Cavity
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Chapter 22, Respiratory System 54
Pressure Relationships in the Thoracic Cavity
Intrapulmonary pressure (Ppul)pressure within the
alveoli
Intrapleural pressure (Pip)pressure within the
pleural cavity
Pressure Relationships
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Chapter 22, Respiratory System 55
Pressure Relationships
Intrapulmonary pressure and intrapleural pressure
fluctuate with the phases of breathing
Intrapulmonary pressure always eventually
equalizes itself with atmospheric pressure
Intrapleural pressure is always less than
intrapulmonary pressure and atmospheric pressure
Pressure Relationships
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Chapter 22, Respiratory System 56
Pressure Relationships
Two forces act to pull the lungs away from thethoracic wall, promoting lung collapse
Elasticity of lungs causes them to assume smallest
possible size
Surface tension of alveolar fluid draws alveoli to
their smallest possible size
Opposing forceelasticity of the chest wall pulls
the thorax outward to enlarge the lungs
Pressure Relationships
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Chapter 22, Respiratory System 57
Pressure Relationships
Figure 22.12
Lung Collapse
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Chapter 22, Respiratory System 58
Lung Collapse
Caused by equalization of the intrapleural pressure
with the intrapulmonary pressure
Transpulmonary pressure keeps the airways open
Transpulmonary pressuredifference between the
intrapulmonary and intrapleural pressures
(PpulPip)
Pulmonary Ventilation
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Chapter 22, Respiratory System 59
Pulmonary Ventilation
A mechanical process that depends on volume
changes in the thoracic cavity
Volume changes lead to pressure changes, which
lead to the flow of gases to equalize pressure
Boyles Law
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Chapter 22, Respiratory System 60
Boyle s Law
Boyles law the relationship between the pressureand volume of gases
P1V1= P2V2
P = pressure of a gas in mm Hg
V = volume of a gas in cubic millimeters
Subscripts 1 and 2 represent the initial and resulting
conditions, respectively
Inspiration
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Chapter 22, Respiratory System 61
Inspiration
The diaphragm and external intercostal muscles(inspiratory muscles) contract and the rib cage rises
The lungs are stretched and intrapulmonary volume
increases
Intrapulmonary pressure drops below atmospheric
pressure (1 mm Hg)
Air flows into the lungs, down its pressure gradient,
until intrapleural pressure = atmospheric pressure
Inspiration
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Chapter 22, Respiratory System 62
Inspiration
Figure 22.13.1
Expiration
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Chapter 22, Respiratory System 63
Expiration
Inspiratory muscles relax and the rib cage descends
due to gravity
Thoracic cavity volume decreases
Elastic lungs recoil passively and intrapulmonaryvolume decreases
Intrapulmonary pressure rises above atmospheric
pressure (+1 mm Hg)
Gases flow out of the lungs down the pressure
gradient until intrapulmonary pressure is 0
Expiration
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Chapter 22, Respiratory System 64
p o
Figure 22.13.2
Physical Factors Influencing Ventilation:
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Chapter 22, Respiratory System 65
Friction is the major nonelastic source of resistance
to airflow
The relationship between flow (F), pressure (P), and
resistance (R) is:
y g
Airway Resistance
P
RF =
Physical Factors Influencing Ventilation:
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Chapter 22, Respiratory System 66
The amount of gas flowing into and out of the
alveoli is directly proportional to P, the pressure
gradient between the atmosphere and the alveoli
Gas flow is inversely proportional to resistance with
the greatest resistance being in the medium-sized
bronchi
y g
Airway Resistance
Airway Resistance
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Chapter 22, Respiratory System 67
y
As airway resistance rises, breathing movements
become more strenuous
Severely constricted or obstructed bronchioles:
Can prevent life-sustaining ventilation
Can occur during acute asthma attacks which stops
ventilation
Epinephrine release via the sympathetic nervous
system dilates bronchioles and reduces air resistance
Alveolar Surface Tension
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Chapter 22, Respiratory System 68
Surface tensionthe attraction of liquid moleculesto one another at a liquid-gas interface
The liquid coating the alveolar surface is always
acting to reduce the alveoli to the smallest possiblesize
Surfactant, a detergent-like complex, reduces
surface tension and helps keep the alveoli from
collapsing
Lung Compliance
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Chapter 22, Respiratory System 69
g p
The ease with which lungs can be expanded
Specifically, the measure of the change in lung
volume that occurs with a given change in
transpulmonary pressure
Determined by two main factors
Distensibility of the lung tissue and surrounding
thoracic cage
Surface tension of the alveoli
Factors That Diminish Lung Compliance
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Chapter 22, Respiratory System 70
g p
Scar tissue or fibrosis that reduces the naturalresilience of the lungs
Blockage of the smaller respiratory passages with
mucus or fluid
Reduced production of surfactant
Decreased flexibility of the thoracic cage or itsdecreased ability to expand
Factors That Diminish Lung Compliance
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Chapter 22, Respiratory System 71
g p
Examples include:
Deformities of thorax
Ossification of the costal cartilage
Paralysis of intercostal muscles
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Chapter 22, Respiratory System 72
22
The Respiratory System
Physiology
Respiratory Volumes
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Chapter 22, Respiratory System 73
p y
Tidal volume (TV)air that moves into and out of
the lungs with each breath (approximately 500 ml)
Inspiratory reserve volume (IRV)air that can be
inspired forcibly beyond the tidal volume (2100
3200 ml)
Expiratory reserve volume (ERV)air that can be
evacuated from the lungs after a tidal expiration
(10001200 ml)
Residual volume (RV)air left in the lungs after
strenuous expiration (1200 ml)
Respiratory Capacities
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Chapter 22, Respiratory System 74
Inspiratory capacity (IC)total amount of air that
can be inspired after a tidal expiration (IRV + TV)
Functional residual capacity (FRC)amount of air
remaining in the lungs after a tidal expiration
(RV + ERV)
Vital capacity (VC)the total amount of
exchangeable air (TV + IRV + ERV)
Total lung capacity (TLC)sum of all lung
volumes (approximately 6000 ml in males)
Dead Space
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Chapter 22, Respiratory System 75
Anatomical dead spacevolume of the conducting
respiratory passages (150 ml)
Alveolar dead spacealveoli that cease to act in gasexchange due to collapse or obstruction
Total dead spacesum of alveolar and anatomical
dead spaces
Pulmonary Function Tests
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Chapter 22, Respiratory System 76
Spirometeran instrument consisting of a hollowbell inverted over water, used to evaluate respiratory
function
Spirometry can distinguish between:
Obstructive pulmonary diseaseincreased airway
resistance
Restrictive disordersreduction in total lung
capacity from structural or functional lung changes
Pulmonary Function Tests
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Chapter 22, Respiratory System 77
Total ventilationtotal amount of gas flow into or
out of the respiratory tract in one minute
Forced vital capacity (FVC)gas forcibly expelledafter taking a deep breath
Forced expiratory volume (FEV)the amount of
gas expelled during specific time intervals of theFVC
Pulmonary Function Tests
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Chapter 22, Respiratory System 78
Increases in TLC, FRC, and RV may occur as a
result of obstructive disease
Reduction in VC, TLC, FRC, and RV result from
restrictive disease
Alveolar Ventilation
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Chapter 22, Respiratory System 79
Alveolar ventilation rate (AVR)measures the flowof fresh gases into and out of the alveoli during a
particular time
Slow, deep breathing increases AVR and rapid,
shallow breathing decreases AVR
AVR = frequency X (TVdead space)
(ml/min) (breaths/min) (ml/breath)
Nonrespiratory Air Movements
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Chapter 22, Respiratory System 80
Most result from reflex action
Examples include: coughing, sneezing, crying,
laughing, hiccupping, and yawning
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What is Composition of Air?
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Chapter 22, Respiratory System 82
Air = 21% O2, 78% N2 and .04% CO2
Alveolar air = 14% O2, 78% N2 and 5.2% CO2
Expired air = 16% O2, 78% N2 and 4.5% CO2
Observations
alveolar air has less O2 since absorbed by blood
mystery-----expired air has more O2 & less CO2 than
alveolar air?
Anatomical dead space = 150 ml of 500 ml of tidal volume
Basic Properties of Gases: Henrys Law
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Chapter 22, Respiratory System 83
When a mixture of gases is in contact with a liquid,
each gas will dissolve in the liquid in proportion toits partial pressure
The amount of gas that will dissolve in a liquid also
depends upon its solubility
Various gases in air have different solubilities:
Carbon dioxide is the most soluble
Oxygen is 1/20thas soluble as carbon dioxide
Nitrogen is practically insoluble in plasma
Hyperbaric Oxygenation
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Chapter 22, Respiratory System 84
Clinical application of Henrys law
Use of pressure to dissolve more O2
in the blood
treatment for patients with anaerobic bacterial infections (tetanus and
gangrene)
anaerobic bacteria die in the presence of O2
Hyperbaric chamber pressure raised to 3 to 4 atmospheres so that
tissues absorb more O2
Used to treat heart disorders, carbon monoxide poisoning,
cerebral edema, bone infections, gas embolisms & crush injuries
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External Respiration: Pulmonary Gas
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Chapter 22, Respiratory System 86
Factors influencing the movement of oxygen and
carbon dioxide across the respiratory membrane
Partial pressure gradients and gas solubilities
Matching of alveolar ventilation and pulmonary
blood perfusion
Structural characteristics of the respiratorymembrane
Exchange
Partial Pressure Gradients and Gas
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Chapter 22, Respiratory System 87
The partial pressure oxygen (PO2) of venous blood
is 40 mm Hg; the partial pressure in the alveoli is
104 mm Hg
This steep gradient allows oxygen partial pressures
to rapidly reach equilibrium (in 0.25 seconds), and
thus blood can move three times as quickly (0.75
seconds) through the pulmonary capillary and stillbe adequately oxygenated
Solubilities
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Partial Pressure Gradients
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Chapter 22, Respiratory System 89
Figure 22.17
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Oxygenation of Blood
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Chapter 22, Respiratory System 91Figure 22.18
Ventilation-Perfusion Coupling
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Chapter 22, Respiratory System 92
Ventilationthe amount of gas reaching the alveoli
Perfusionthe blood flow reaching the alveoli
Ventilation and perfusion must be tightly regulatedfor efficient gas exchange
Changes in PCO2in the alveoli cause changes in thediameters of the bronchioles
Passageways servicing areas where alveolar carbondioxide is high dilate
Those serving areas where alveolar carbon dioxideis low constrict
Ventilation-Perfusion Coupling
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Chapter 22, Respiratory System 93Figure 22.19
Surface Area and Thickness of the Respiratory
M b
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Chapter 22, Respiratory System 94
Respiratory membranes: Are only 0.5 to 1 m thick, allowing for efficient
gas exchange
Have a total surface area (in males) of about 60 m2
(40 times that of ones skin)
Thicken if lungs become waterlogged andedematous, whereby gas exchange is inadequate
and oxygen deprivation results
Decrease in surface area with emphysema, whenwalls of adjacent alveoli break through
Membrane
Th f i h b
Internal Respiration
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Chapter 22, Respiratory System 95
The factors promoting gas exchange between
systemic capillaries and tissue cells are the same as
those acting in the lungs
The partial pressures and diffusion gradients are
reversed
PO2in tissue is always lower than in systemic
arterial blood
PO2of venous blood draining tissues is 40 mm Hgand PCO2is 45 mm Hg
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Oxygen Transport: Role of Hemoglobin
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Chapter 22, Respiratory System 97
Each Hb molecule binds four oxygen atoms in a
rapid and reversible process
The hemoglobin-oxygen combination is called
oxyhemoglobin (HbO2)
Hemoglobin that has released oxygen is calledreduced hemoglobin (HHb)
HHb + O2
Lungs
Tissues
HbO2 + H+
Hemoglobin (Hb)
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Chapter 22, Respiratory System 98
Saturated hemoglobinwhen all four hemes of the
molecule are bound to oxygen Partially saturated hemoglobinwhen one to three
hemes are bound to oxygen
The rate that hemoglobin binds and releases oxygenis regulated by:
PO2, temperature, blood pH, PCO2, and the
concentration of BPG (an organic chemical)
These factors ensure adequate delivery ofoxygen to tissue cells
Influence of PO2on Hemoglobin Saturation
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Chapter 22, Respiratory System99
Hemoglobin saturation plotted against PO2produces
a oxygen-hemoglobin dissociation curve
98% saturated arterial blood contains 20 ml oxygen
per 100 ml blood (20 vol %)
As arterial blood flows through capillaries, 5 ml
oxygen are released
The saturation of hemoglobin in arterial bloodexplains why breathing deeply increases the PO2but
has little effect on oxygen saturation in hemoglobin
Hemoglobin Saturation Curve
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Chapter 22, Respiratory System100
Hemoglobin is almost completely saturated at a PO2of 70 mm Hg
Further increases in PO2produce only smallincreases in oxygen binding
Oxygen loading and delivery to tissue is adequate
when PO2is below normal levels
Hemoglobin Saturation Curve
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Chapter 22, Respiratory System101
Only 2025% of bound oxygen is unloaded duringone systemic circulation
If oxygen levels in tissues drop:
More oxygen dissociates from hemoglobin and isused by cells
Respiratory rate or cardiac output need not increase
Hemoglobin Saturation Curve
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Chapter 22, Respiratory System102
Figure 22.20
Other Factors Influencing Hemoglobin
Saturation
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Chapter 22, Respiratory System103
Temperature, H+, PCO2, and BPG
Modify the structure of hemoglobin and alter itsaffinity for oxygen
Increases of these factors:
Decrease hemoglobins affinity for oxygen
Enhance oxygen unloading from the blood
Decreases act in the opposite manner
These parameters are all high in systemic capillarieswhere oxygen unloading is the goal
Saturation
Factors That Increase Release of Oxygen by
Hemoglobin
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Chapter 22, Respiratory System104
As cells metabolize glucose, carbon dioxide is
released into the blood causing:
Increases in PCO2and H+concentration in capillary
blood
Declining pH (acidosis), which weakens thehemoglobin-oxygen bond (Bohr effect)
Metabolizing cells have heat as a byproduct and therise in temperature increases BPG synthesis
All these factors ensure oxygen unloading in thevicinity of working tissue cells
Hemoglobin
Hemoglobin and Oxygen Partial Pressure
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Chapter 22, Respiratory System105
Blood is almost fully saturated
at pO2 of 60mm
people OK at high
altitudes & with somedisease
Between 40 & 20 mm Hg, large
amounts of O2 are released
as in areas of need like
contracting muscle
lungsmuscle tissues
pCO2 & Oxygen Release
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Chapter 22, Respiratory System106
As pCO2 rises with
exercise, O2 is released
more easily
CO2 converts to carbonic
acid & becomes H+ and
bicarbonate ions &
lowers pH.
Acidity & Oxygen Affinity for Hb
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Chapter 22, Respiratory System107
As H+ increases (decrease
in pH), O2 affinity for
Hb decreases
Bohr effect allows the bloodto unload oxygen
H+ binds to hemoglobin &
alters it
O2 left behind in needy
tissues
Temperature & Oxygen Release
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Chapter 22, Respiratory System108
As temperatureincreases, more O2 is
released
Metabolic activity &heat increases
Hemoglobin-Nitric Oxide Partnership
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Chapter 22, Respiratory System109
Nitric oxide (NO) is a vasodilator that plays a role in
blood pressure regulation
Hemoglobin is a vasoconstrictor and a nitric oxide
scavenger (heme destroys NO)
However, as oxygen binds to hemoglobin:
Nitric oxide binds to a cysteine amino acid on
hemoglobin
Bound nitric oxide is protected from degradation by
hemoglobins iron
Hemoglobin-Nitric Oxide Partnership
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Chapter 22, Respiratory System110
The hemoglobin is released as oxygen is unloaded,
causing vasodilation
As deoxygenated hemoglobin picks up carbon
dioxide, it also binds nitric oxide and carries these
gases to the lungs for unloading
Carbon Dioxide Transport
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Chapter 22, Respiratory System111
Carbon dioxide is transported in the blood in threeforms
Dissolved in plasma7 to 10%
Chemically bound to hemoglobin20% is carried
in RBCs as carbaminohemoglobin
Bicarbonate ion in plasma70% is transported asbicarbonate (HCO3
)
C b di id diff i RBC d bi
Transport and Exchange of Carbon Dioxide
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Chapter 22, Respiratory System112
Carbon dioxide diffuses into RBCs and combines
with water to form carbonic acid (H2CO3), which
quickly dissociates into hydrogen ions and
bicarbonate ions
In RBCs, carbonic anhydrase reversibly catalyzesthe conversion of carbon dioxide and water to
carbonic acid
CO2 + H2O H2CO3 H+
+ HCO3
Carbon
dioxideWater
Carbonic
acid
Hydrogen
ion
Bicarbonate
ion
Transport and Exchange of Carbon Dioxide
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Chapter 22, Respiratory System113
Figure 22.22a
Transport and Exchange of Carbon Dioxide
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Chapter 22, Respiratory System
114
At the tissues:
Bicarbonate quickly diffuses from RBCs into the
plasma
The chloride shiftto counterbalance the outrush
of negative bicarbonate ions from the RBCs,
chloride ions (Cl) move from the plasma into the
erythrocytes
Transport and Exchange of Carbon Dioxide
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Chapter 22, Respiratory System
115
At the lungs, these processes are reversed
Bicarbonate ions move into the RBCs and bind
with hydrogen ions to form carbonic acid
Carbonic acid is then split by carbonic anhydrase to
release carbon dioxide and water
Carbon dioxide then diffuses from the blood intothe alveoli
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Haldane Effect
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Chapter 22, Respiratory System
117
The amount of carbon dioxide transported is
markedly affected by the PO2
Haldane effectthe lower the PO2and hemoglobin
saturation with oxygen, the more carbon dioxide can
be carried in the blood
Haldane Effect
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Chapter 22, Respiratory System
118
At the tissues, as more carbon dioxide enters theblood:
More oxygen dissociates from hemoglobin (Bohr
effect)
More carbon dioxide combines with hemoglobin,
and more bicarbonate ions are formed
This situation is reversed in pulmonary circulation
Haldane Effect
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Chapter 22, Respiratory System
119Figure 22.23
Influence of Carbon Dioxide on Blood pH
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Chapter 22, Respiratory System
120
The carbonic acidbicarbonate buffer system resistsblood pH changes
If hydrogen ion concentrations in blood begin to
rise, excess H+is removed by combining withHCO3
If hydrogen ion concentrations begin to drop,
carbonic acid dissociates, releasing H+
Influence of Carbon Dioxide on Blood pH
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Chapter 22, Respiratory System
121
Changes in respiratory rate can also:
Alter blood pH Provide a fast-acting system to adjust pH when it
is disturbed by metabolic factors
I nterActive Physiology:
Respiratory System: Gas TransportPLAY
Control of Respiration:
Medullary Respiratory Centers
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Chapter 22, Respiratory System
122
The dorsal respiratory group (DRG), or inspiratory
center:
Is located near the root of nerve IX
Appears to be the pacesetting respiratory center
Excites the inspiratory muscles and sets eupnea(12-15 breaths/minute)
Becomes dormant during expiration
The ventral respiratory group (VRG) is involved inforced inspiration and expiration
edu y esp o y Ce e s
Control of Respiration:
Medullary Respiratory Centers
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Chapter 22, Respiratory System 123Figure 22.24
y p y
Control of Respiration:
Pons Respiratory Centers
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Chapter 22, Respiratory System 124
Pons centers:
Influence and modify activity of the medullary
centers
Smooth out inspiration and expiration transitions
and vice versa
The pontine respiratory group (PRG)continuouslyinhibits the inspiration center
p y
Respiratory Rhythm
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Chapter 22, Respiratory System 125
A result of reciprocal inhibition of theinterconnected neuronal networks in the medulla
Other theories include
Inspiratory neurons are pacemakers and have
intrinsic automaticity and rhythmicity
Stretch receptors in the lungs establish respiratoryrhythm
Depth and Rate of Breathing
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Chapter 22, Respiratory System 126
Inspiratory depth is determined by how actively the
respiratory center stimulates the respiratory muscles
Rate of respiration is determined by how long theinspiratory center is active
Respiratory centers in the pons and medullaare
sensitive to both excitatory and inhibitory stimuli
Medullary Respiratory Centers
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Chapter 22, Respiratory System 127Figure 22.25
Depth and Rate of Breathing: Reflexes
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Chapter 22, Respiratory System 128
Pulmonary irritant reflexesirritants promote
reflexive constriction of air passages
Inflation reflex (Hering-Breuer)stretch receptors
in the lungs are stimulated by lung inflation
Upon inflation, inhibitory signals are sent to the
medullary inspiration center to end inhalation andallow expiration
Depth and Rate of Breathing: Higher Brain
Centers
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Chapter 22, Respiratory System 129
Hypothalamic controls act through the limbic
system to modify rate and depth of respiration
Example: breath holding that occurs in anger
A rise in body temperature acts to increaserespiratory rate
Cortical controls are direct signals from the cerebral
motor cortex that bypass medullary controls
Examples: voluntary breath holding, taking a deep
breath
Depth and Rate of Breathing: PCO2
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Chapter 22, Respiratory System 130
Changing PCO2levels are monitored by
chemoreceptors of the brain stem
Carbon dioxide in the blood diffuses into the
cerebrospinal fluid where it is hydrated
Resulting carbonic acid dissociates, releasing
hydrogen ions
PCO2levels rise (hypercapnia) resulting in increaseddepth and rate of breathing
Depth and Rate of Breathing: PCO2
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Chapter 22, Respiratory System 131Figure 22.26
Depth and Rate of Breathing: PCO2
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Chapter 22, Respiratory System 132
Hyperventilationincreased depth and rate ofbreathing that:
Quickly flushes carbon dioxide from the blood
Occurs in response to hypercapnia
Though a rise CO2acts as the original stimulus,
control of breathing at rest is regulated by thehydrogen ion concentration in the brain
Depth and Rate of Breathing: PCO2
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Chapter 22, Respiratory System 133
Hypoventilationslow and shallow breathing due to
abnormally low PCO2levels
Apnea (breathing cessation) may occur until PCO2
levels rise
Arterial oxygen levels are monitored by the aortic
Depth and Rate of Breathing: PCO2
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Chapter 22, Respiratory System 134
Arterial oxygen levels are monitored by the aortic
and carotid bodies
Substantial drops in arterial PO2(to 60 mm Hg) are
needed before oxygen levels become a major
stimulus for increased ventilation If carbon dioxide is not removed (e.g., as in
emphysema and chronic bronchitis), chemoreceptors
become unresponsive to PCO2chemical stimuli
In such cases, PO2levels become the principal
respiratory stimulus (hypoxic drive)
Depth and Rate of Breathing: Arterial pH
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Chapter 22, Respiratory System 135
Changes in arterial pH can modify respiratory rate
even if carbon dioxide and oxygen levels are normal
Increased ventilation in response to falling pH is
mediated by peripheral chemoreceptors
Peripheral Chemoreceptors
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Chapter 22, Respiratory System 136Figure 22.27
Depth and Rate of Breathing: Arterial pH
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Chapter 22, Respiratory System 137
Acidosis may reflect:
Carbon dioxide retention
Accumulation of lactic acid
Excess fatty acids in patients with diabetes mellitus
Respiratory system controls will attempt to raise the
pH by increasing respiratory rate and depth
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Respiratory Adjustments: Exercise
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Chapter 22, Respiratory System 139
As exercise begins:
Ventilation increases abruptly, rises slowly, and
reaches a steady state
When exercise stops:
Ventilation declines suddenly, then gradually
decreases to normal
Respiratory Adjustments: Exercise
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Chapter 22, Respiratory System 140
Neural factors bring about the above changes,
including:
Psychic stimuli
Cortical motor activation
Excitatory impulses from proprioceptors in muscles
I nterActive Physiology:
Respiratory System: Control of RespirationPLAY
Respiratory Adjustments: High Altitude
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Chapter 22, Respiratory System 141
The body responds to quick movement to high
altitude (above 8000 ft) with symptoms of acute
mountain sicknessheadache, shortness of breath,
nausea, and dizziness
Respiratory Adjustments: High Altitude
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Chapter 22, Respiratory System 142
Acclimatizationrespiratory and hematopoieticadjustments to altitude include:
Increased ventilation2-3 L/min higher than at sea
level
Chemoreceptors become more responsive to PCO2
Substantial decline in PO2stimulates peripheralchemoreceptors
Pneumothorax Pleural cavities are sealed
iti t t th
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Chapter 22, Respiratory System 143
cavities not open to theoutside
Injuries to the chest wallthat let air enter theintrapleural space
causes a pneumothorax
collapsed lung on sameside as injury
surface tension and recoilof elastic fibers causesthe lung to collapse
Smokers Lowered Respiratory Efficiency
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Chapter 22, Respiratory System 144
Smoker is easily winded with moderate exercise
nicotine constricts terminal bronchioles
carbon monoxide in smoke binds to hemoglobin
irritants in smoke cause excess mucus secretion
irritants inhibit movements of cilia
in time destroys elastic fibers in lungs & leads to emphysema
trapping of air in alveoli & reduced gas exchange
Every thirteen seconds someone dies from a smoking-related
disease.
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Chapter 22, Respiratory System 145
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Chapter 22, Respiratory System 146
Chronic Obstructive Pulmonary Disease(COPD)
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Chapter 22, Respiratory System 147
Exemplified by chronic bronchitis and obstructive
emphysema
Patients have a history of:
Smoking
Dyspnea, where labored breathingoccurs and getsprogressively worse
Coughing and frequent pulmonary infections
COPD victims develop respiratory failureaccompanied by hypoxemia, carbon dioxideretention, and respiratory acidosis
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Pathogenesis of COPD
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Chapter 22, Respiratory System 149Figure 22.28
Characterized by dyspnea wheezing and chest
Asthma
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Chapter 22, Respiratory System 150
Characterized by dyspnea, wheezing, and chest
tightness
Active inflammation of the airways precedes
bronchospasms
Airway inflammation is an immune response caused
by release of IL-4 and IL-5, which stimulate IgE and
recruit inflammatory cells
Airways thickened with inflammatory exudates
magnify the effect of bronchospasms
Tuberculosis
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Chapter 22, Respiratory System 151
Infectious disease caused by the bacterium
Mycobacterium tuberculosis
Symptoms include fever, night sweats, weight loss,a racking cough, and splitting headache
Treatment entails a 12-month course of antibiotics
Accounts for 1/3 of all cancer deaths in the U.S.
Lung Cancer
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Chapter 22, Respiratory System 152
90% of all patients with lung cancer were smokers
The three most common types are:
Squamous cell carcinoma (20-40% of cases)arises
in bronchial epithelium
Adenocarcinoma (25-35% of cases)originates inperipheral lung area
Small cell carcinoma (20-25% of cases)containslymphocyte-like cells that originate in the primary
bronchi and subsequently metastasize
Olfactory placodes invaginate into olfactory pits byh
Developmental Aspects
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Chapter 22, Respiratory System 153
the 4thweek
Laryngotracheal buds are present by the 5thweek
Mucosae of the bronchi and lung alveoli are presentby the 8thweek
By the 28thweek, a baby born prematurely canbreathe on its own
During fetal life, the lungs are filled with fluid andblood bypasses the lungs
Gas exchange takes place via the placenta
Respiratory System Development
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Chapter 22, Respiratory System 154
Figure 22.29
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