Transcript Respiratory System

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Anatomy of the Respiratory System
Pulmonary Ventilation
Gas Exchange and Transport
Respiratory Disorders
22-1
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Nose
Pharynx
Larynx
Trachea
Bronchi
Lungs
22-2
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Airflow in lungs
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Conducting division = Passages for airflow
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Alveoli
Upper respiratory tract = Parts in the head and neck
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Nostrils to bronchioles
Respiratory division = Gas exchange regions
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bronchi  bronchioles  alveoli
Nose through larynx
Lower respiratory tract = Parts in the thorax
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Trachea through lungs
22-3
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Functions
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warms, cleanses, humidifies inhaled air
detects odors
resonating chamber that amplifies the voice
22-4
22-5
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Superior, middle and inferior nasal conchae
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3 folds of tissue on lateral wall of nasal fossa
mucous membranes supported by thin scroll-like
turbinate bones
Meatuses
narrow air passage beneath each conchae
 narrowness and turbulence ensures air contacts
mucous membranes
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22-6
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Olfactory mucosa
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Respiratory mucosa
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lines roof of nasal fossa
lines rest of nasal cavity with ciliated pseudostratified
epithelium
Defensive role of mucosa
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mucus (from goblet cells) traps inhaled particles
 bacteria destroyed by lysozyme
22-7
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Function of cilia of respiratory epithelium
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Erectile tissue of inferior concha
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sweep debris-laden mucus into pharynx to be swallowed
venous plexus that rhythmically engorges with blood and
shifts flow of air from one side of fossa to the other once
or twice an hour to prevent drying
Spontaneous epistaxis (nosebleed)
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most common site is inferior concha
22-8
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Nasopharynx
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pseudostratified epithelium
posterior to choanae, dorsal to soft
palate
receives auditory tubes and contains
pharyngeal tonsil
90 downward turn traps large particles
(>10m)
22-9
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Oropharynx
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stratifeid squamous epithelium
space between soft palate and root of
tongue, inferiorly as far as hyoid bone,
contains palatine and lingual tonsils
22-10
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Laryngopharynx
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stratified squamous
hyoid bone to level of cricoid cartilage
22-11
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Glottis – vocal cords and opening between
Epiglottis
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flap of tissue that guards glottis
directs food and drink to esophagus
22-12
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Epiglottic cartilage - most superior
Thyroid cartilage – largest; laryngeal
prominence
Cricoid cartilage - connects larynx to
trachea
Arytenoid cartilages (2) - posterior to
thyroid cartilage
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Corniculate cartilages (2) attached to arytenoid cartilages
like a pair of little horns
Cuneiform cartilages (2) - support
soft tissue between arytenoids
and epiglottis
22-13
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Rigid tube ~4.5 in. long and
~2.5 in. diameter.
Anterior to esophagus
Supported by 16 to 20 Cshaped cartilaginous rings
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opening in rings faces
posteriorly towards esophagus
trachealis spans opening in
rings, adjusts airflow by
expanding or contracting
Larynx and trachea lined with
ciliated pseudostratified
epithelium which functions
as mucociliary escalator
22-14
22-15
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Right lung has 3 lobes
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Left Lung has 2 lobes
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Superior
Middle (smallest)
Inferior
Room for the heart
Carina
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Primary bronchi (C-shaped rings)
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from trachea; after 2-3 cm enter
hilum of lungs
right bronchus slightly wider and
more vertical (aspiration)
Secondary (lobar) bronchi
(overlapping plates)
 one for each lobe of lung
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Tertiary (segmental) bronchi
(overlapping plates)
 10 right, 8 left
22-17
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Bronchioles (lack cartilage)
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layer of smooth muscle
pulmonary lobule is the
portion ventilated by one
bronchiole
divides into 50 - 80 terminal
bronchioles
Each divides into 2-10
alveolar ducts; end in alveolar
sacs
Alveoli
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main site for gas exchange
22-18
22-19
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Similar to the pericardium except around the lungs
Visceral (on lungs) and parietal (lines rib cage) pleurae
Pleural cavity - space between pleurae, lubricated with
fluid
Functions
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reduce friction
compartmentalization
22-20
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Breathing (pulmonary ventilation) – one cycle of
inspiration and expiration
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quiet respiration – at rest
forced respiration – during exercise
Flow of air in and out of lung requires a pressure
difference between air pressure within lungs and
outside body
22-21
22-22
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Diaphragm (dome
shaped)
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Scalenes
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stiffen thoracic cage;
increases diameter
Pectoralis minor, sternocleidomastoid and erector spinae
muscles
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hold first pair of ribs
stationary
External and internal
intercostals
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contraction flattens
diaphragm
used in forced inspiration
Abdominals and latissimus dorsi
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forced expiration (to sing, cough, sneeze)
22-23
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Breathing depends on repetitive
stimuli from brain
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Neurons in medulla oblongata and
pons control unconscious breathing
Voluntary control provided by motor
cortex
Inspiratory neurons: fire during
inspiration
Expiratory neurons: fire during forced
expiration
Fibers of phrenic nerve go to
diaphragm; intercostal nerves to
intercostal muscles
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22-24
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Respiratory nuclei in medulla
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The Dorsal Respiratory Group
(formerly called the inspiratory
center)
The Ventral Respiratory Group
(formerly called the expiratory
center )
Pons
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The Pontine Respiratory Center
(formerly the pneumotaxic and
apneustic centers)
22-25
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From limbic system and hypothalamus
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respiratory effects of pain and emotion
From airways and lungs
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irritant receptors in respiratory mucosa
 stimulate vagal afferents to medulla, results in bronchoconstriction
or coughing
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stretch receptors in airways - inflation reflex
 excessive inflation triggers reflex
 stops inspiration
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From chemoreceptors
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monitor blood pH, CO2 and O2 levels
22-26
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Peripheral chemoreceptors
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found in major blood vessels
 aortic bodies
 signals medulla by vagus
nerves
 carotid bodies
 signals medulla by
glossopharyngeal nerves
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Central chemoreceptors
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in medulla
 primarily monitor pH of CSF
22-27
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Atmospheric pressure drives respiration
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1 atmosphere (atm) = 760 mmHg
Intrapulmonary pressure and lung volume
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pressure is inversely proportional to volume
 for a given amount of gas, as volume , pressure  and as
volume , pressure 
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Pressure gradients
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difference between atmospheric and intrapulmonary
pressure
created by changes in volume thoracic cavity
22-28
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Atmospheric pressure
drives respiration
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 intrapulmonary
pressure
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1 atmosphere (atm) =
760 mmHg
lungs expand with
visceral pleura
500 ml of air flows with
a quiet breath
22-29
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During quiet breathing, expiration achieved by elasticity of
lungs and thoracic cage
As volume of thoracic cavity , intrapulmonary pressure 
and air is expelled
After inspiration, phrenic nerves continue to stimulate
diaphragm to produce a braking action to elastic recoil
Internal intercostal muscles depress the ribs
Contract abdominal muscles
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 intra-abdominal pressure forces diaphragm upward
 pressure on thoracic cavity
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22-31
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Presence of air in pleural cavity
Collapse of lung (or part of lung) is called atelectasis
22-32
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Atelectasis is the decrease or loss
of air in all or part of the lung
Tumors obstructing a bronchus
Foreign body (an inhaled marble?)
Serious pneumonia
Lack of surfactant
Smoke inhalation
Post-operative complication
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Pulmonary compliance
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distensibility of lungs
Bronchiolar diameter
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Compliance is reduced
by smoking and by
fibrotic conditions such
as sarcoidosis or lupus
Asthma
primary control over resistance to airflow
bronchoconstriction
 triggered by airborne irritants, cold air, parasympathetic
stimulation, histamine
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bronchodilation
 sympathetic nerves, epinephrine
22-34
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Thin film of water needed for gas exchange
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creates surface tension that acts to collapse alveoli and distal
bronchioles
Pulmonary surfactant decreases surface tension
Premature infants that lack surfactant suffer from
respiratory distress syndrome
22-35
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Spirometer - measures ventilation
Respiratory volumes
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tidal volume: volume of air in one quiet breath
inspiratory reserve volume
 air in excess of tidal inspiration that can be inhaled with
maximum effort
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expiratory reserve volume
 air in excess of tidal expiration that can be exhaled with
maximum effort
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residual volume (keeps alveoli inflated)
 air remaining in lungs after maximum expiration
22-36
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Respiratory volumes
tidal volume:
 inspiratory reserve volume
 expiratory reserve volume
 residual volume
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Vital capacity
total amount of air that can be
exhaled with effort after
maximum inspiration
 assesses strength of thoracic
muscles and pulmonary function
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Age -  lung compliance, respiratory muscles weaken
Exercise - maintains strength of respiratory muscles
Body size - proportional, big body/large lungs
Restrictive disorders
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 compliance and vital capacity
Obstructive disorders
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interfere with airflow, expiration requires more effort or less
complete
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Mixture of gases; each contributes its partial pressure
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At sea level 1 atm. of pressure = 760 mmHg
Air is about 79% nitrogen = 597 mmHg
Air is only about 21% oxygen = 159 mmHg
Air has almost no carbon dioxide = 0.3 mmHg
In Denver (or Reno) atmospheric pressure = 625 (to 645) mmHg
Air is about 79% nitrogen = 494 (510) mmHg
Air is only about 21% oxygen = 131 (135) mmHg
Air has almost no carbon dioxide = 0.3 mmHg
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Important for gas exchange
between air in lungs and
blood in capillaries
Gases diffuse down their
concentration gradients
Amount of gas that dissolves
in water is determined by its
solubility in water and its
partial pressure in air
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Time required for gases to
equilibrate = 0.25 sec
RBC transit time at rest = 0.75
sec to pass through alveolar
capillary
RBC transit time with
vigorous exercise = 0.3 sec
What percentage of O2
loading at 0.75 sec transit
time is now possible?
22-41
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Membrane thickness - only
0.5 m thick
Membrane surface area - 100
ml blood in alveolar
capillaries, spread over 70 m2
Ventilation-perfusion coupling
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areas of good ventilation need
good perfusion (vasodilation)
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Concentration in arterial blood
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20 ml/dl
 98.5% bound to hemoglobin
 1.5% dissolved
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Binding to hemoglobin
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each heme group of 4 globin chains
may bind O2
oxyhemoglobin (HbO2 )
deoxyhemoglobin (HHb)
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As bicarbonate (and carbonic acid) - 90%
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CO2 + H2O  H2CO3  HCO3- + H+
As carbaminohemoglobin (HbCO2)- 5% binds to amino
groups of Hb (and plasma proteins)
As dissolved gas - 5%
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CO2 loading
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carbonic anhydrase in RBC catalyzes
 CO2 + H2O  H2CO3  HCO3- + H+
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chloride shift
 keeps reaction proceeding
 exchanges HCO3- for Cl (H+ binds to hemoglobin)
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O2 unloading
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H+ binding to HbO2  its affinity for O2
 Hb arrives 97% saturated
 Hb leaves 75% saturated
 venous reserve
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Reactions in the alveolus are the
reverse of systemic gas exchange
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Active tissues need oxygen!
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ambient PO2: active tissue has  PO2 ; O2 is released
temperature: active tissue has  temp; O2 is released
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Active tissues need oxygen!
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Bohr effect: active tissue has  CO2, which lowers pH (muscle
burn); O2 is released
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Haldane effect
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HbO2 does not bind CO2 as well as deoxyhemoglobin
low level of HbO2 (as in active tissue) enables blood to
transport more CO2
22-51
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Rate and depth of breathing adjusted to
maintain levels of:
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pH
 PCO
2
 PO
2
Let’s look at their effects on respiration:
22-52
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pH of CSF (most powerful respiratory stimulus)
Respiratory acidosis (pH < 7.35) caused by failure of
pulmonary ventilation
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hypercapnia: PCO2 > 43 mmHg
 CO2 easily crosses blood-brain barrier
 in CSF the CO2 reacts with water and releases H+
 central chemoreceptors strongly stimulate inspiratory center
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“blowing off ” CO2 pushes reaction to the left
CO2 (expired) + H2O  H2CO3  HCO3- + H+
The induction of hyperventilation reduces H+ (reduces acid)
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Respiratory alkalosis (pH > 7.45) caused by
hyperventilation
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hypocapnia: PCO2 < 37 mmHg
The induction of hypoventilation ( CO2), pushes reaction
to the right
 CO2 + H2O  H2CO3  HCO3- + H+
 H+ (increases acid), lowers pH to normal
pH imbalances can have metabolic causes
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eg - uncontrolled diabetes mellitus can cause acidosis
 fat oxidation causes ketoacidosis, may be compensated for
by Kussmaul respiration (deep rapid breathing)
22-54
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Hypoxia is a deficiency in the amount of oxygen reaching the
tissues
Dyspnea is difficult or labored breathing, “air hunger”
Cyanosis is a blueish color of the skin and mucous membranes
Causes of hypoxia
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hypoxemic hypoxia - usually due to inadequate pulmonary gas
exchange
 high altitudes, drowning, aspiration, respiratory arrest, degenerative lung
diseases, CO poisoning
ischemic hypoxia - inadequate circulation
 anemic hypoxia - anemia
 histotoxic hypoxia - metabolic poison (cyanide)
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Primary effect of hypoxia
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tissue necrosis, organs with high metabolic demands affected first
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Oxygen toxicity: pure O2 breathed at 2.5 atm or
greater
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generates free radicals and H2O2 which destroys enzymes
damages
 CNS – seizures, coma death
 Eyes – blindness
 Lungs – painful breathing
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Hyperbaric oxygen (high % O2 under increased
atmospheric pressures)
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formerly used to treat premature infants
22-56
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Asthma (if it is poorly
controlled)
 allergen triggers
histamine release
 intense
bronchoconstriction
(blocks air flow)
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COPD is most often
associated with
smoking
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chronic bronchitis
leads to emphysema
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Chronic bronchitis
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cilia immobilized and  in number
goblet cells enlarge and produce excess mucus
sputum formed (mucus and cellular debris)
 ideal growth media for bacteria
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leads to chronic infection and bronchial inflammation
22-58
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Emphysema
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alveolar walls break down
 much less respiratory membrane for gas exchange
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lungs fibrotic and less elastic
air passages collapse
 obstruct outflow of air
 air trapped in lungs
22-59
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 pulmonary compliance and vital capacity
Hypoxemia, hypercapnia, respiratory acidosis
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hypoxemia stimulates erythropoietin release and leads to
polycythemia
Cor pulmonale
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hypertrophy and potential failure of right heart due to
obstruction of pulmonary circulation
22-60
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Lung cancer accounts for more deaths than any other
form of cancer
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90% originate in primary bronchi
Tumor invades bronchial wall, compresses airway; may
cause atelectasis
Often first sign is coughing up blood
Metastasis is rapid; usually occurs by time of diagnosis
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most important cause is smoking (15 carcinogens)
common sites: pericardium, heart, bones, liver, lymph nodes
and brain
Prognosis poor after diagnosis
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only 7% of patients survive 5 years
22-61