Transcript Respiratory Physiology - Department of Zoology, UBC

Respiratory
physiology:
Respiration
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Ventilation: Movement of air into and out of
lungs
External respiration: Gas exchange between
air in lungs and blood
Transport of oxygen and carbon dioxide in
the blood
Internal respiration: Gas exchange between
the blood and tissues
Respiratory System Functions
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Gas exchange: Oxygen enters blood and carbon
dioxide leaves
Regulation of blood pH: Altered by changing blood
carbon dioxide levels
Voice production: Movement of air past vocal folds
makes sound and speech
Olfaction: Smell occurs when airborne molecules
drawn into nasal cavity
Protection: Against microorganisms by preventing
entry and removing them
Respiratory System Divisions
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Upper tract
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Nose, pharynx and
associated
structures
Lower tract
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Larynx, trachea,
bronchi, lungs
Nasal Cavity and Pharynx
Nose and Pharynx
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Nose
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External nose
Nasal cavity
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Functions
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Passageway for air
Cleans the air
Humidifies, warms air
Smell
Along with paranasal
sinuses are resonating
chambers for speech
Pharynx
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Common opening for
digestive and respiratory
systems
Three regions
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Nasopharynx
Oropharynx
Laryngopharynx
Larynx
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Functions
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Maintain an open passageway for air movement
Epiglottis and vestibular folds prevent swallowed material from
moving into larynx
Vocal folds are primary source of sound production
Vocal Folds
Trachea
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Windpipe
Divides to
form
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Primary
bronchi
Carina:
Cough
reflex
Tracheobronchial Tree
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Conducting zone
Trachea to terminal bronchioles which is ciliated
for removal of debris
 Passageway for air movement
 Cartilage holds tube system open and smooth
muscle controls tube diameter
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Respiratory zone
Respiratory bronchioles to alveoli
 Site for gas exchange
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Tracheobronchial Tree
Bronchioles and Alveoli
Alveolus and Respiratory
Membrane
Lungs
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Two lungs: Principal organs of respiration
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Right lung: Three lobes
Left lung: Two lobes
Divisions
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Lobes, bronchopulmonary segments, lobules
Thoracic Walls
Muscles of Respiration
Thoracic Volume
Pleura
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Pleural fluid produced by pleural membranes
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Acts as lubricant
Helps hold parietal and visceral pleural membranes
together
Ventilation
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Movement of air into and out of lungs
Air moves from area of higher pressure to area
of lower pressure
Pressure is inversely related to volume
Alveolar Pressure Changes
Changing Alveolar Volume
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Lung recoil
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Causes alveoli to collapse resulting from
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Elastic recoil and surface tension
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Surfactant: Reduces tendency of lungs to collapse
Pleural pressure
Negative pressure can cause alveoli to expand
 Pneumothorax is an opening between pleural
cavity and air that causes a loss of pleural
pressure
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Normal Breathing Cycle
Compliance
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Measure of the ease with which lungs and
thorax expand
The greater the compliance, the easier it is for a
change in pressure to cause expansion
 A lower-than-normal compliance means the
lungs and thorax are harder to expand
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Conditions that decrease compliance
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Pulmonary fibrosis
Pulmonary edema
Respiratory distress syndrome
Pulmonary Volumes
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Tidal volume
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Inspiratory reserve volume
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Amount of air inspired forcefully after inspiration of normal tidal
volume
Expiratory reserve volume
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Volume of air inspired or expired during a normal inspiration or
expiration
Amount of air forcefully expired after expiration of normal tidal
volume
Residual volume
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Volume of air remaining in respiratory passages and lungs after the
most forceful expiration
Pulmonary Capacities
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Inspiratory capacity
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Functional residual capacity
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Expiratory reserve volume plus the residual volume
Vital capacity
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Tidal volume plus inspiratory reserve volume
Sum of inspiratory reserve volume, tidal volume, and expiratory
reserve volume
Total lung capacity
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Sum of inspiratory and expiratory reserve volumes plus the tidal
volume and residual volume
Spirometer and Lung
Volumes/Capacities
Minute and Alveolar Ventilation
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Minute ventilation: Total amount of air moved
into and out of respiratory system per minute
Respiratory rate or frequency: Number of
breaths taken per minute
Anatomic dead space: Part of respiratory system
where gas exchange does not take place
Alveolar ventilation: How much air per minute
enters the parts of the respiratory system in
which gas exchange takes place
Physical Principles of Gas
Exchange
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Partial pressure
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The pressure exerted by each type of gas in a mixture
Dalton’s law
Water vapor pressure
Diffusion of gases through liquids
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Concentration of a gas in a liquid is determined by its
partial pressure and its solubility coefficient
Henry’s law
Physical Principles of Gas
Exchange
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Diffusion of gases through the respiratory
membrane
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Depends on membrane’s thickness, the diffusion coefficient of
gas, surface areas of membrane, partial pressure of gases in
alveoli and blood
Relationship between ventilation and
pulmonary capillary flow
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Increased ventilation or increased pulmonary capillary blood
flow increases gas exchange
Physiologic shunt is deoxygenated blood returning from lungs
Oxygen and Carbon Dioxide
Diffusion Gradients
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Oxygen
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Moves from alveoli into
blood. Blood is almost
completely saturated with
oxygen when it leaves the
capillary
P02 in blood decreases
because of mixing with
deoxygenated blood
Oxygen moves from
tissue capillaries into the
tissues
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Carbon dioxide
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Moves from tissues into
tissue capillaries
Moves from pulmonary
capillaries into the
alveoli
Changes in Partial Pressures
Hemoglobin and Oxygen
Transport
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Oxygen is transported by hemoglobin (98.5%) and
is dissolved in plasma (1.5%)
Oxygen-hemoglobin dissociation curve shows that
hemoglobin is almost completely saturated when
P02 is 80 mm Hg or above. At lower partial
pressures, the hemoglobin releases oxygen.
A shift of the curve to the left because of an
increase in pH, a decrease in carbon dioxide, or a
decrease in temperature results in an increase in the
ability of hemoglobin to hold oxygen
Hemoglobin and Oxygen
Transport
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A shift of the curve to the right because of a decrease
in pH, an increase in carbon dioxide, or an increase in
temperature results in a decrease in the ability of
hemoglobin to hold oxygen
The substance 2.3-bisphosphoglycerate increases the
ability of hemoglobin to release oxygen
Fetal hemoglobin has a higher affinity for oxygen than
does maternal
Oxygen-Hemoglobin
Dissociation Curve at Rest
Bohr effect:
Temperature effects:
Shifting the Curve
Transport of Carbon Dioxide
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Carbon dioxide is transported as bicarbonate ions
(70%) in combination with blood proteins (23%)
and in solution with plasma (7%)
Hemoglobin that has released oxygen binds more
readily to carbon dioxide than hemoglobin that has
oxygen bound to it (Haldane effect)
In tissue capillaries, carbon dioxide combines with
water inside RBCs to form carbonic acid which
dissociates to form bicarbonate ions and hydrogen
ions
Transport of Carbon Dioxide
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In lung capillaries, bicarbonate ions and hydrogen
ions move into RBCs and chloride ions move out.
Bicarbonate ions combine with hydrogen ions to
form carbonic acid. The carbonic acid is converted
to carbon dioxide and water. The carbon dioxide
diffuses out of the RBCs.
Increased plasma carbon dioxide lowers blood pH.
The respiratory system regulates blood pH by
regulating plasma carbon dioxide levels
CO2 Transport and Cl- Movement
Ventilation-perfusion coupling:
Respiratory Areas in Brainstem
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Medullary respiratory center
Dorsal groups stimulate the diaphragm
 Ventral groups stimulate the intercostal and
abdominal muscles
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Pontine (pneumotaxic) respiratory group
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Involved with switching between inspiration and
expiration
Respiratory Structures in Brainstem
Rhythmic Ventilation
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Starting inspiration
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Increasing inspiration
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Medullary respiratory center neurons are continuously active
Center receives stimulation from receptors and simulation from parts of
brain concerned with voluntary respiratory movements and emotion
Combined input from all sources causes action potentials to stimulate
respiratory muscles
More and more neurons are activated
Stopping inspiration
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Neurons stimulating also responsible for stopping inspiration and receive
input from pontine group and stretch receptors in lungs. Inhibitory
neurons activated and relaxation of respiratory muscles results in
expiration.
Modification of Ventilation
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Cerebral and limbic
system
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Chemical control
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Respiration can be
voluntarily controlled
and modified by
emotions
Carbon dioxide is major
regulator
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Increase or decrease in pH
can stimulate chemosensitive area, causing a
greater rate and depth of
respiration
Oxygen levels in blood
affect respiration when a
50% or greater decrease
from normal levels exists
Modifying Respiration
Regulation of Blood pH and
Gases
Herring-Breuer Reflex
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Limits the degree of inspiration and prevents
overinflation of the lungs
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Infants
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Reflex plays a role in regulating basic rhythm of breathing
and preventing overinflation of lungs
Adults
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Reflex important only when tidal volume large as in
exercise
Ventilation in Exercise
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Ventilation increases abruptly
At onset of exercise
 Movement of limbs has strong influence
 Learned component
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Ventilation increases gradually
After immediate increase, gradual increase occurs
(4-6 minutes)
 Anaerobic threshold is highest level of exercise
without causing significant change in blood pH
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If exceeded, lactic acid produced by skeletal muscles
Effects of Aging
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Vital capacity and maximum minute
ventilation decrease
Residual volume and dead space increase
Ability to remove mucus from respiratory
passageways decreases
Gas exchange across respiratory membrane is
reduced