Chapter 23
Respiratory System
Albert Grazia, M.S., N.D.
(516) 486-8332
www.naturedoc.info
Albert Grazia, M.S., N.D.
www.naturedoc.info
1
Chapter 23
The Respiratory System
• Cells continually use O2 & release CO2
• Respiratory system designed for gas exchange
• Cardiovascular system transports gases in
blood
• Failure of either system
– rapid cell death from O2 starvation
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Respiratory System Anatomy
•
•
•
•
•
•
•
Nose
Pharynx = throat
Larynx = voicebox
Trachea = windpipe
Bronchi = airways
Lungs
Locations of infections
– upper respiratory tract is above vocal cords
– lower respiratory tract is below vocal cords
STRUCTURE
FUNCTION
nose / nasal
cavity
warms, moistens, & filters air as it
is inhaled
pharynx
(throat)
larynx
passageway for air, leads to
trachea
the voice box, where vocal chords
are located
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trachea
(windpipe)
tube from pharynx to bronchi
rings of cartilage provide
structure, keeps the windpipe
"open"
trachea is lined with fine hairs
called cilia which filter air before
it reaches the lungs
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bronchi
bronchioles
alveoli
two branches at the end of the
trachea, each lead to a lung
a network of smaller branches leading
from the bronchi into the lung tissue &
ultimately to air sacs
the functional respiratory units in the
lung where gases (oxygen & carbon
dioxide) are exchanged (enter & exit
the blood stream)
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External Nasal Structures
• Skin, nasal bones, & cartilage lined with mucous membrane
• Openings called external nares or nostrils
Nose -- Internal Structures
•
•
•
•
•
Large chamber within the skull
Roof is made up of ethmoid and floor is hard palate
Internal nares (choanae) are openings to pharynx
Nasal septum is composed of bone & cartilage
Bony swelling or conchae on lateral walls
Functions of the Nasal Structures
• Olfactory epithelium for sense of smell
• Pseudostratified ciliated columnar with goblet
cells lines nasal cavity
– warms air due to high vascularity
– mucous moistens air & traps dust
– cilia move mucous towards pharynx
• Paranasal sinuses open into nasal cavity
– found in ethmoid, sphenoid, frontal & maxillary
– lighten skull & resonate voice
Rhinoplasty
• Commonly called a “nose job”
• Surgical procedure done for cosmetic reasons /
fracture or septal repair
• Procedure
–
–
–
–
local and general anesthetic
nasal cartilage is reshaped through nostrils
bones fractured and repositioned
internal packing & splint while healing
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Pharynx
• Muscular tube (5 inch long) hanging from skull
– skeletal muscle & mucous membrane
• Extends from internal nares to cricoid cartilage
• Functions
– passageway for food and air
– resonating chamber for speech production
– tonsil (lymphatic tissue) in the walls protects
entryway into body
• Distinct regions -- nasopharynx, oropharynx
and laryngopharynx
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Nasopharynx
• From choanae to soft palate
– openings of auditory (Eustachian) tubes from middle ear cavity
– adenoids or pharyngeal tonsil in roof
• Passageway for air only
– pseudostratified ciliated columnar epithelium with goblet
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Oropharynx
• From soft palate to epiglottis
– fauces is opening from mouth into oropharynx
– palatine tonsils found in side walls, lingual tonsil in tongue
• Common passageway for food & air
– stratified squamous epithelium
Laryngopharynx
• Extends from epiglottis to cricoid cartilage
• Common passageway for food & air & ends as esophagus
inferiorly
– stratified squamous epithelium
Cartilages of the Larynx
• Thyroid cartilage forms Adam’s apple
• Epiglottis---leaf-shaped piece of elastic cartilage
– during swallowing, larynx moves upward
– epiglottis bends to cover glottis
• Cricoid cartilage---ring of cartilage attached to
top of trachea
• Pair of arytenoid cartilages sit upon cricoid
– many muscles responsible for their movement
– partially buried in vocal folds (true vocal cords)
Larynx
• Cartilage & connective tissue tube
• Anterior to C4 to C6
• Constructed of 3 single & 3 paired cartilages
Vocal Cords
• False vocal cords (ventricular folds) found above
vocal folds (true vocal cords)
• True vocal cords attach to arytenoid cartilages
The Structures of Voice Production
• True vocal cord contains both skeletal muscle
and an elastic ligament (vocal ligament)
• When 10 intrinsic muscles of the larynx
contract, move cartilages & stretch vocal cord
tight
• When air is pushed past tight ligament, sound
is produced (the longer & thicker vocal cord
in male produces a lower pitch of sound)
• The tighter the ligament, the higher the pitch
• To increase volume of sound, push air harder
Movement of Vocal Cords
• Opening and closing of the vocal folds occurs during
breathing and speech
Speech and Whispering
• Speech is modified sound made by the larynx.
• Speech requires pharynx, mouth, nasal cavity &
sinuses to resonate that sound
• Tongue & lips form words
• Pitch is controlled by tension on vocal folds
– pulled tight produces higher pitch
– male vocal folds are thicker & longer so
vibrate more slowly producing a lower pitch
• Whispering is forcing air through almost closed
rima glottidis -- oral cavity alone forms speech
Trachea
• Size is 5 in long & 1in diameter
• Extends from larynx to T5 anterior to the esophagus and then
splits into bronchi
• Layers:
– mucosa = pseudostratified columnar with cilia & goblet
– submucosa = loose connective tissue & seromucous glands
– hyaline cartilage = 16 to 20 incomplete rings
• open side facing esophagus contains trachealis m. (smooth)
• internal ridge on last ring called carina
– adventitia binds it to other organs
Trachea and Bronchial Tree
• Full extent of airways is visible starting at the
larynx and trachea
Histology of the Trachea
• Ciliated pseudostratified columnar epithelium
• Hyaline cartilage as C-shaped structure closed by
trachealis muscle
Airway Epithelium
• Ciliated pseudostratified columnar epithelium with
goblet cells produce a moving mass of mucus.
Tracheostomy and Intubation
• Reestablishing airflow past an airway obstruction
– crushing injury to larynx or chest
– swelling that closes airway
– vomit or foreign object
• Tracheostomy is incision in trachea below cricoid
cartilage if larynx is obstructed
• Intubation is passing a tube from mouth or nose
through larynx and trachea
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Bronchi and Bronchioles
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Primary bronchi supply each lung
Secondary bronchi supply each lobe of the lungs (3 right + 2 left)
Tertiary bronchi supply each bronchopulmonary segment
Repeated branchings called bronchioles form a bronchial tree
Histology of Bronchial Tree
• Epithelium changes from pseudostratified ciliated
columnar to nonciliated simple cuboidal as pass
deeper into lungs
• Incomplete rings of cartilage replaced by rings of
smooth muscle & then connective tissue
– sympathetic NS & adrenal gland release epinephrine
that relaxes smooth muscle & dilates airways
– asthma attack or allergic reactions constrict distal
bronchiole smooth muscle
– nebulization therapy = inhale mist with chemicals that
relax muscle & reduce thickness of mucus
Pleural Membranes & Pleural Cavity
• Visceral pleura covers lungs --- parietal pleura lines
ribcage & covers upper surface of diaphragm
• Pleural cavity is potential space between ribs & lungs
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
• Blood vessels & airways enter lungs at hilus
• Forms root of lungs
• Covered with pleura (parietal becomes visceral)
Structures within a Lobule of Lung
• Branchings of single
arteriole, venule &
bronchiole are wrapped by
elastic CT
• Respiratory bronchiole
– simple squamous
• Alveolar ducts surrounded
by alveolar sacs & alveoli
– sac is 2 or more alveoli
sharing a common opening
Histology of Lung Tissue
Photomicrograph of
lung tissue showing
bronchioles, alveoli
and alveolar ducts.
Cells Types of the Alveoli
• Type I alveolar cells
– simple squamous cells where gas exchange occurs
• Type II alveolar cells (septal cells)
– free surface has microvilli
– secrete alveolar fluid containing surfactant
• Alveolar dust cells
– wandering macrophages remove debris
Alveolar-Capillary Membrane
• Respiratory membrane = 1/2 micron thick
• Exchange of gas from alveoli to blood
• 4 Layers of membrane to cross
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alveolar epithelial wall of type I cells
alveolar epithelial basement membrane
capillary basement membrane
endothelial cells of capillary
• Vast surface area = handball court
Details of Respiratory Membrane
• 4 layers comprise the respiratory membrane
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Double Blood Supply to the Lungs
• Deoxygenated blood arrives through pulmonary
trunk from the right ventricle
• Bronchial arteries branch off of the aorta to
supply oxygenated blood to lung tissue
• Venous drainage returns all blood to heart
• Less pressure in venous system
• Pulmonary blood vessels constrict in response to
low O2 levels so as not to pick up CO2 on their
way through the lungs
Breathing or Pulmonary Ventilation
• Air moves into lungs when pressure inside lungs
is less than atmospheric pressure
– How is this accomplished?
• Air moves out of the lungs when pressure inside
lungs is greater than atmospheric pressure
• Atmospheric pressure = 1 atm or 760mm Hg
• There are no muscles in your lungs. They do not
actively pump air in & out, in & out. The muscle
responsible for breathing actually lies below the
lungs. It is like a rubber sheet that separates your chest
cavity & your abdominal cavity. It's name is diaphragm.
• When you inhale, the diaphragm contracts & moves
downward, which creates more space in your chest
cavity & draws air into the lungs. When you exhale, the
diaphragm relaxes & moves upward, forcing air out of
the lungs.
• A common demonstration of the mechanics behind
breathing involves a bell jar, some glass tubing, and a
couple of balloons. Like so:
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• Mechanics of Breathing
• To take a breath in, the external intercostal muscles
contract, moving the ribcage up and out. The
diaphragm moves down at the same time, creating
negative pressure within the thorax. The lungs are held
to the thoracic wall by the pleural membranes, and so
expand outwards as well. This creates negative pressure
within the lungs, and so air rushes in through the upper
and lower airways.
• Expiration is mainly due to the natural elasticity of the
lungs, which tend to collapse if they are not held against
the thoracic wall. This is the mechanism behind lung
collapse if there is air in the pleural space
(pneumothorax).
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Boyle’s Law
• As the size of closed container decreases, pressure
inside is increased
• The molecules have less wall area to strike so the
pressure on each inch of area increases.
Dimensions of the Chest Cavity
• Breathing in requires muscular activity & chest size changes
• Contraction of the diaphragm flattens the dome and
increases the vertical dimension of the chest
Quiet Inspiration
• Diaphragm moves 1 cm & ribs lifted by muscles
• Intrathoracic pressure falls and 2-3 liters inhaled
Quiet Expiration
• Passive process with no muscle action
• Elastic recoil & surface tension in alveoli pulls inward
• Alveolar pressure increases & air is pushed out
Labored Breathing
• Forced expiration
– abdominal mm force
diaphragm up
– internal intercostals
depress ribs
• Forced inspiration
– sternocleidomastoid,
scalenes & pectoralis
minor lift chest
upwards as you gasp
for air
Intrathoracic
Pressures
• Always subatmospheric (756 mm Hg)
• As diaphragm contracts intrathoracic pressure decreases even
more (754 mm Hg)
• Helps keep parietal & visceral pleura stick together
Summary of Breathing
• Alveolar pressure decreases & air rushes in
• Alveolar pressure increases & air rushes out
Alveolar Surface Tension
• Thin layer of fluid in alveoli causes inwardly
directed force = surface tension
– water molecules strongly attracted to each other
• Causes alveoli to remain as small as possible
• Detergent-like substance called surfactant
produced by Type II alveolar cells
– lowers alveolar surface tension
– insufficient in premature babies so that alveoli
collapse at end of each exhalation
Pneumothorax
• Pleural cavities are sealed cavities not open to
the outside
• Injuries to the chest wall that let air enter the
intrapleural space
– causes a pneumothorax
– collapsed lung on same side as injury
– surface tension and recoil of elastic fibers causes
the lung to collapse
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Compliance of the Lungs
• Ease with which lungs & chest wall expand
depends upon elasticity of lungs & surface
tension
• Some diseases reduce compliance
– tuberculosis forms scar tissue
– pulmonary edema --- fluid in lungs & reduced
surfactant
– paralysis
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Airway Resistance
• Resistance to airflow depends upon
airway size
– increase size of chest
• airways increase in diameter
– contract smooth muscles in airways
• decreases in diameter
Breathing Patterns
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Eupnea = normal quiet breathing
Apnea = temporary cessation of breathing
Dyspnea =difficult or labored breathing
Tachypnea = rapid breathing
Diaphragmatic breathing = descent of diaphragm
causes stomach to bulge during inspiration
• Costal breathing = just rib activity involved
Modified Respiratory Movements
• Coughing
– deep inspiration, closure of rima glottidis &
strong expiration blasts air out to clear
respiratory passages
• Hiccuping
– spasmodic contraction of diaphragm & quick
closure of rima glottidis produce sharp
inspiratory sound
• Chart of others on page 826
Lung Volumes and Capacities
• Tidal volume = amount air moved during quiet breathing
• MVR= minute ventilation is amount of air moved in a minute
• Reserve volumes ---- amount you can breathe either in or out above that
amount of tidal volume
• Residual volume = 1200 mL permanently trapped air in system
• Vital capacity & total lung capacity are sums of the other volumes
Dalton’s Law
• Each gas in a mixture of gases exerts its own
pressure
– as if all other gases were not present
– partial pressures denoted as p
• Total pressure is sum of all partial pressures
– atmospheric pressure (760 mm Hg) = pO2 + pCO2
+ pN2 + pH2O
– to determine partial pressure of O2-- multiply 760
by % of air that is O2 (21%) = 160 mm Hg
What is Composition of Air?
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Air = 21% O2, 79% N2 and .04% CO2
Alveolar air = 14% O2, 79% N2 and 5.2% CO2
Expired air = 16% O2, 79% 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
Henry’s Law
• Quantity of a gas that will dissolve in a liquid
depends upon the amount of gas present and its
solubility coefficient
– explains why you can breathe compressed air while
scuba diving despite 79% Nitrogen
• N2 has very low solubility unlike CO2 (soda cans)
• dive deep & increased pressure forces more N2 to dissolve in
the blood (nitrogen narcosis)
• decompression sickness if come back to surface too fast or
stay deep too long
• Breathing O2 under pressure dissolves more O2 in
blood
Hyperbaric Oxygenation
• Clinical application of Henry’s 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
• Gases diffuse from areas of
high partial pressure to areas
of low partial pressure
• Exchange of gas between air
& blood
• Deoxygenated blood
becomes saturated
• Compare gas movements in
pulmonary capillaries to
tissue capillaries
Rate of Diffusion of Gases
• Depends upon partial pressure of gases in air
– p O2 at sea level is 160 mm Hg
– 10,000 feet is 110 mm Hg/50,000 feet is 18 mm Hg
• Large surface area of our alveoli
• Diffusion distance is very small
• Solubility & molecular weight of gases
– O2 smaller molecule diffuses somewhat faster
– CO2 dissolves 24X more easily in water so net outward
diffusion of CO2 is much faster
– disease produces hypoxia before hypercapnia
– lack of O2 before too much CO2
Internal Respiration
• Exchange of gases between
blood & tissues
• Conversion of oxygenated
blood into deoxygenated
• Observe diffusion of O2 inward
– at rest 25% of available O2
enters cells
– during exercise more O2 is
absorbed
• Observe diffusion of CO2
outward
Oxygen Transport in the Blood
• Oxyhemoglobin contains 98.5% chemically
combined oxygen and hemoglobin
– inside red blood cells
• Does not dissolve easily in water
– only 1.5% transported dissolved in blood
• Only the dissolved O2 can diffuse into tissues
• Factors affecting dissociation of O2 from
hemoglobin are important
• Oxygen dissociation curve shows levels of
saturation and oxygen partial pressures
Hemoglobin and Oxygen Partial Pressure
• Blood is almost fully
saturated at pO2 of
60mm
– people OK at high
altitudes & with some
disease
• Between 40 & 20 mm
Hg, large amounts of
O2 are released as in
areas of need like
contracting muscle
Acidity & Oxygen Affinity for Hb
• As acidity
increases, O2
affinity for
Hb decreases
• Bohr effect
• H+ binds to
hemoglobin
& alters it
• O2 left
behind in
needy tissues
pCO2 & Oxygen Release
• As pCO2 rises
with exercise,
O2 is released
more easily
• CO2 converts to
carbonic acid &
becomes H+ and
bicarbonate ions
& lowers pH.
Temperature & Oxygen Release
• As temperature
increases, more
O2 is released
• Metabolic activity
& heat
• More BPG, more
O2 released
– RBC activity
– hormones like
thyroxine &
growth hormone
Oxygen Affinity & Fetal Hemoglobin
• Differs from adult
in structure &
affinity for O2
• When pO2 is low,
can carry more
O2
• Maternal blood in
placenta has less
O2
Carbon Monoxide Poisoning
• CO from car exhaust & tobacco smoke
• Binds to Hb heme group more successfully
than O2
• CO poisoning
• Treat by administering pure O2
Red blood cells pick up CO quicker than they
pick up oxygen.
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Carbon Dioxide Transport
• 100 ml of blood carries 55 ml of CO2
• Is carried by the blood in 3 ways
– dissolved in plasma
– combined with the globin part of Hb
molecule forming carbaminohemoglobin
– as part of bicarbonate ion
• CO2 + H2O combine to form carbonic acid that
dissociates into H+ and bicarbonate ion
Summary of Gas Exchange & Transport
Role of the Respiratory Center
• Respiratory mm.
controlled by
neurons in pons &
medulla
• 3 groups of neurons
– medullary
rhythmicity
– pneumotaxic
– apneustic centers
Medullary Rhythmicity Area
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•
•
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Controls basic rhythm of respiration
Inspiration for 2 seconds, expiration for 3
Autorhythmic cells active for 2 seconds then inactive
Expiratory neurons inactive during most quiet breathing only
active during high ventilation rates
Pneumotaxic & Apneustic Areas
• Pneumotaxic Area
– constant inhibitory impulses to inspiratory area
• neurons trying to turn off inspiration before lungs too
expanded
• Apneustic Area
– stimulatory signals to inspiratory area to prolong
inspiration
– if pneumotaxic area is sick
Regulation of Respiratory Center
• Cortical Influences
– voluntarily alter breathing patterns
– limitations are buildup of CO2 & H+ in blood
– inspiratory center is stimulated by increase in
either
– if you hold breathe until you faint----breathing will
resume
Chemical Regulation of Respiration
• Central chemoreceptors in medulla
– respond to changes in H+ or pCO2
– hypercapnia = slight increase in pCO2 is noticed
• Peripheral chemoreceptors
– respond to changes in H+ , pO2 or PCO2
– aortic body---in wall of aorta
• nerves join vagus
– carotid bodies--in walls of common carotid arteries
• nerves join glossopharyngeal nerve
Negative Feedback Regulation of Breathing
• Negative feedback control of
breathing
• Increase in arterial pCO2
• Stimulates receptors
• Inspiratory center
• Muscles of respiration
contract more frequently &
forcefully
• pCO2 Decreases
Types of Hypoxia
• Deficiency of O2 at tissue level
• Types of hypoxia
– hypoxic hypoxia--low pO2 in arterial blood
• high altitude, fluid in lungs & obstructions
– anemic hypoxia--too little functioning Hb
• hemorrhage or anemia
– ischemic hypoxia--blood flow is too low
– histotoxic hypoxia--cyanide poisoning
• blocks metabolic stages & O2 usage
Respiratory Influences & Reflex Behaviors
• Quick breathing rate response to exercise
– input from proprioceptors
• Inflation Reflex (Hering-Breurer reflex)
– big deep breath stretching receptors produces urge to
exhale
• Factors increasing breathing rate
– emotional anxiety, temperature increase or drop in
blood pressure
• Apnea or cessation of breathing
– by sudden plunge into cold water, sudden pain,
irritation of airway
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Exercise and the Respiratory System
• During exercise, muscles consume large amounts of O2
& produce large amounts CO2
• Pulmonary ventilation must increase
– moderate exercise increases depth of breathing,
– strenuous exercise also increases rate of breathing
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Exercise and the Respiratory System
• Abrupt changes at start of exercise are neural
– anticipation & sensory signals from proprioceptors
– impulses from motor cortex
• Chemical & physical changes are important
– decrease in pO2, increase in pCO2 & increased
temperature
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Smokers Lowered Respiratory Efficiency
• 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
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Developmental Anatomy of Respiratory System
• 4 weeks endoderm of
foregut gives rise to
lung bud
• Differentiates into
epithelial lining of
airways
• 6 months closed-tubes
swell into alveoli of
lungs
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Aging & the Respiratory System
• Respiratory tissues & chest wall become more
rigid
• Vital capacity decreases to 35% by age 70.
• Decreases in macrophage activity
• Diminished ciliary action
• Decrease in blood levels of O2
• Result is an age-related susceptibility to
pneumonia or bronchitis
Disorders of the Respiratory System
• Asthma
• Chronic obstructive pulmonary disease
– Emphysema
– Chronic bronchitis
– Lung cancer
•
•
•
•
•
Pneumonia
Tuberculosis
Influenza
Pulmonary Edema
Cystic fibrosis
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