Respiratory System
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Transcript Respiratory System
Anatomy of the Respiratory System
Pulmonary Ventilation
Gas Exchange and Transport
Respiratory Disorders
22-1
Nose
Pharynx
Larynx
Trachea
Bronchi
Lungs
22-2
Airflow in lungs
Conducting division = Passages for airflow
Alveoli
Upper respiratory tract = Parts in the head and neck
Nostrils to bronchioles
Respiratory division = Gas exchange regions
bronchi bronchioles alveoli
Nose through larynx
Lower respiratory tract = Parts in the thorax
Trachea through lungs
22-3
Functions
warms, cleanses, humidifies inhaled air
detects odors
resonating chamber that amplifies the voice
22-4
22-5
Superior, middle and inferior nasal conchae
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
22-6
Olfactory mucosa
Respiratory mucosa
lines roof of nasal fossa
lines rest of nasal cavity with ciliated pseudostratified
epithelium
Defensive role of mucosa
mucus (from goblet cells) traps inhaled particles
bacteria destroyed by lysozyme
22-7
Function of cilia of respiratory epithelium
Erectile tissue of inferior concha
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)
most common site is inferior concha
22-8
Nasopharynx
pseudostratified epithelium
posterior to choanae, dorsal to soft
palate
receives auditory tubes and contains
pharyngeal tonsil
90 downward turn traps large particles
(>10m)
22-9
Oropharynx
stratifeid squamous epithelium
space between soft palate and root of
tongue, inferiorly as far as hyoid bone,
contains palatine and lingual tonsils
22-10
Laryngopharynx
stratified squamous
hyoid bone to level of cricoid cartilage
22-11
Glottis – vocal cords and opening between
Epiglottis
flap of tissue that guards glottis
directs food and drink to esophagus
22-12
Epiglottic cartilage - most superior
Thyroid cartilage – largest; laryngeal
prominence
Cricoid cartilage - connects larynx to
trachea
Arytenoid cartilages (2) - posterior to
thyroid cartilage
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
Rigid tube ~4.5 in. long and
~2.5 in. diameter.
Anterior to esophagus
Supported by 16 to 20 Cshaped cartilaginous rings
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
Right lung has 3 lobes
Left Lung has 2 lobes
Superior
Middle (smallest)
Inferior
Room for the heart
Carina
Primary bronchi (C-shaped rings)
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
Tertiary (segmental) bronchi
(overlapping plates)
10 right, 8 left
22-17
Bronchioles (lack cartilage)
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
main site for gas exchange
22-18
22-19
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
reduce friction
compartmentalization
22-20
Breathing (pulmonary ventilation) – one cycle of
inspiration and expiration
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
Diaphragm (dome
shaped)
Scalenes
stiffen thoracic cage;
increases diameter
Pectoralis minor, sternocleidomastoid and erector spinae
muscles
hold first pair of ribs
stationary
External and internal
intercostals
contraction flattens
diaphragm
used in forced inspiration
Abdominals and latissimus dorsi
forced expiration (to sing, cough, sneeze)
22-23
Breathing depends on repetitive
stimuli from brain
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
22-24
Respiratory nuclei in medulla
The Dorsal Respiratory Group
(formerly called the inspiratory
center)
The Ventral Respiratory Group
(formerly called the expiratory
center )
Pons
The Pontine Respiratory Center
(formerly the pneumotaxic and
apneustic centers)
22-25
From limbic system and hypothalamus
respiratory effects of pain and emotion
From airways and lungs
irritant receptors in respiratory mucosa
stimulate vagal afferents to medulla, results in bronchoconstriction
or coughing
stretch receptors in airways - inflation reflex
excessive inflation triggers reflex
stops inspiration
From chemoreceptors
monitor blood pH, CO2 and O2 levels
22-26
Peripheral chemoreceptors
found in major blood vessels
aortic bodies
signals medulla by vagus
nerves
carotid bodies
signals medulla by
glossopharyngeal nerves
Central chemoreceptors
in medulla
primarily monitor pH of CSF
22-27
Atmospheric pressure drives respiration
1 atmosphere (atm) = 760 mmHg
Intrapulmonary pressure and lung volume
pressure is inversely proportional to volume
for a given amount of gas, as volume , pressure and as
volume , pressure
Pressure gradients
difference between atmospheric and intrapulmonary
pressure
created by changes in volume thoracic cavity
22-28
Atmospheric pressure
drives respiration
intrapulmonary
pressure
1 atmosphere (atm) =
760 mmHg
lungs expand with
visceral pleura
500 ml of air flows with
a quiet breath
22-29
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
intra-abdominal pressure forces diaphragm upward
pressure on thoracic cavity
22-30
22-31
Presence of air in pleural cavity
Collapse of lung (or part of lung) is called atelectasis
22-32
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
Pulmonary compliance
distensibility of lungs
Bronchiolar diameter
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
bronchodilation
sympathetic nerves, epinephrine
22-34
Thin film of water needed for gas exchange
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
Spirometer - measures ventilation
Respiratory volumes
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
expiratory reserve volume
air in excess of tidal expiration that can be exhaled with
maximum effort
residual volume (keeps alveoli inflated)
air remaining in lungs after maximum expiration
22-36
Respiratory volumes
tidal volume:
inspiratory reserve volume
expiratory reserve volume
residual volume
Vital capacity
total amount of air that can be
exhaled with effort after
maximum inspiration
assesses strength of thoracic
muscles and pulmonary function
Age - lung compliance, respiratory muscles weaken
Exercise - maintains strength of respiratory muscles
Body size - proportional, big body/large lungs
Restrictive disorders
compliance and vital capacity
Obstructive disorders
interfere with airflow, expiration requires more effort or less
complete
22-38
Mixture of gases; each contributes its partial pressure
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
22-39
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
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
Membrane thickness - only
0.5 m thick
Membrane surface area - 100
ml blood in alveolar
capillaries, spread over 70 m2
Ventilation-perfusion coupling
areas of good ventilation need
good perfusion (vasodilation)
22-42
Concentration in arterial blood
20 ml/dl
98.5% bound to hemoglobin
1.5% dissolved
Binding to hemoglobin
each heme group of 4 globin chains
may bind O2
oxyhemoglobin (HbO2 )
deoxyhemoglobin (HHb)
As bicarbonate (and carbonic acid) - 90%
CO2 + H2O H2CO3 HCO3- + H+
As carbaminohemoglobin (HbCO2)- 5% binds to amino
groups of Hb (and plasma proteins)
As dissolved gas - 5%
22-44
CO2 loading
carbonic anhydrase in RBC catalyzes
CO2 + H2O H2CO3 HCO3- + H+
chloride shift
keeps reaction proceeding
exchanges HCO3- for Cl (H+ binds to hemoglobin)
O2 unloading
H+ binding to HbO2 its affinity for O2
Hb arrives 97% saturated
Hb leaves 75% saturated
venous reserve
22-47
Reactions in the alveolus are the
reverse of systemic gas exchange
22-48
Active tissues need oxygen!
ambient PO2: active tissue has PO2 ; O2 is released
temperature: active tissue has temp; O2 is released
22-49
Active tissues need oxygen!
Bohr effect: active tissue has CO2, which lowers pH (muscle
burn); O2 is released
22-50
Haldane effect
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
Rate and depth of breathing adjusted to
maintain levels of:
pH
PCO
2
PO
2
Let’s look at their effects on respiration:
22-52
pH of CSF (most powerful respiratory stimulus)
Respiratory acidosis (pH < 7.35) caused by failure of
pulmonary ventilation
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
“blowing off ” CO2 pushes reaction to the left
CO2 (expired) + H2O H2CO3 HCO3- + H+
The induction of hyperventilation reduces H+ (reduces acid)
22-53
Respiratory alkalosis (pH > 7.45) caused by
hyperventilation
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
eg - uncontrolled diabetes mellitus can cause acidosis
fat oxidation causes ketoacidosis, may be compensated for
by Kussmaul respiration (deep rapid breathing)
22-54
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
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)
Primary effect of hypoxia
tissue necrosis, organs with high metabolic demands affected first
22-55
Oxygen toxicity: pure O2 breathed at 2.5 atm or
greater
generates free radicals and H2O2 which destroys enzymes
damages
CNS – seizures, coma death
Eyes – blindness
Lungs – painful breathing
Hyperbaric oxygen (high % O2 under increased
atmospheric pressures)
formerly used to treat premature infants
22-56
Asthma (if it is poorly
controlled)
allergen triggers
histamine release
intense
bronchoconstriction
(blocks air flow)
COPD is most often
associated with
smoking
chronic bronchitis
leads to emphysema
Chronic bronchitis
cilia immobilized and in number
goblet cells enlarge and produce excess mucus
sputum formed (mucus and cellular debris)
ideal growth media for bacteria
leads to chronic infection and bronchial inflammation
22-58
Emphysema
alveolar walls break down
much less respiratory membrane for gas exchange
lungs fibrotic and less elastic
air passages collapse
obstruct outflow of air
air trapped in lungs
22-59
pulmonary compliance and vital capacity
Hypoxemia, hypercapnia, respiratory acidosis
hypoxemia stimulates erythropoietin release and leads to
polycythemia
Cor pulmonale
hypertrophy and potential failure of right heart due to
obstruction of pulmonary circulation
22-60
Lung cancer accounts for more deaths than any other
form of cancer
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
most important cause is smoking (15 carcinogens)
common sites: pericardium, heart, bones, liver, lymph nodes
and brain
Prognosis poor after diagnosis
only 7% of patients survive 5 years
22-61