The Mechanics of Breathing I
Topics covered:
Coronal section through the chest showing the lungs in he pleural cavity
with the vesceral pleura covering the lungs and the parietal pleura lining
the pleural cavity.
Negative (subatmospheric) pressure in the pleural space
Pneumothorax
Why air enters the pleural space when either the lungs or the chest wall
are punctured.
Lung Compliance & measuring lung compliance in a living person.
The relationship between inflation pressure of excised lungs and their
volume shown on a graph and how to estimate lung compliances from
such a graph
The lungs' elasticity in terms of the elastin fibres in their structure and the
surface tension of air/liquid interface that lines them
The equation for Laplace's law and its terms
Laplace's law and applying it to liquid-lined spheres such as alveoli, and
using the law to explain how changes in alveolar radius and the surface
tension of alvelar lining fluid determine the pressure needed to keep the
alveolus inflated.
The composition of pulmonary surfactant and name the cells which
secrete it.
How pulomonary surfactant molecules are arranged at the air/liquid
interface in the lung and in the liquid hydrophase.
The three essential roles of surfactant in the lung.
How surfactant can be displaced from the alveolar lining and the
consequences of this, and how collapsed alveoli can be expanded and
relined with surfactant
The effect of pulmonary fibrosis on lung compliance and the effect this
has on patients' breathing
The origin of infant respiratory distress of the newborn, the effect it has
on infants' lungs and breathing, what sort of infants are most likely to
have the syndrome (and why) and the principles for preventing it.
The structure of the pleural cavity
How we inflate and deflate our lungs
Pneumothorax
Lung compliance
Factors that alter lung compliance
Breathing in is an active process, breathing out (at rest) is just relaxing of these
muscles.
The lungs are not attached to the chest wall, they slip against the chest wall. The lungs
have elastic properties.
, Before inspiration, alveolar pressure is zero (equal to atmospheric). The intrapleural
pressure is negative as the opposing forces of the lungs trying to collapse (recoil) and
chest expand creates the negative space which holds the airways open.
During inspiration, the inspiratory muscles contract and the alveolar pressure (P alv)
becomes LESS than the atmospheric pressure (Patm) which is why air flows in and the
alveoli expand. Because lung volume increases, the elastic recoil strength of the lung
also increases, as a result intrapleural pressure becomes even more negative. At the
peak of quiet inspiration, lung volume is FRC + TV.
The inspiratory capacity (IC) is the maximum volume of gas that can be inhaled from
the end of resting exhalation, it is equal to the sum of tidal and inspiratory reserve
volume.
The inspiratory reserve volume (IRV) is the additional air you can get into the lungs at
the end of normal tidal volume (normal breath)
During expiration, alveolar pressure becomes greater than atmospheric due to being
compressed by the elastic forces of the lung, so air flows down the pressure gradient,
out of the lungs and the alveoli become return to their original size.
The functional residual capacity (FRC) is the volume of air present in the lungs at the
end of passive expiration, at FRC the elastic recoil forces of the lungs and chest wall
are equal but opposite and there is no exertion by diaphragm or other respiratory
muscles
The expiratory reserve volume (ERV) is the additional air that can be forcibly exhaled
after the expiration of a normal tidal volume.
Topics covered:
Coronal section through the chest showing the lungs in he pleural cavity
with the vesceral pleura covering the lungs and the parietal pleura lining
the pleural cavity.
Negative (subatmospheric) pressure in the pleural space
Pneumothorax
Why air enters the pleural space when either the lungs or the chest wall
are punctured.
Lung Compliance & measuring lung compliance in a living person.
The relationship between inflation pressure of excised lungs and their
volume shown on a graph and how to estimate lung compliances from
such a graph
The lungs' elasticity in terms of the elastin fibres in their structure and the
surface tension of air/liquid interface that lines them
The equation for Laplace's law and its terms
Laplace's law and applying it to liquid-lined spheres such as alveoli, and
using the law to explain how changes in alveolar radius and the surface
tension of alvelar lining fluid determine the pressure needed to keep the
alveolus inflated.
The composition of pulmonary surfactant and name the cells which
secrete it.
How pulomonary surfactant molecules are arranged at the air/liquid
interface in the lung and in the liquid hydrophase.
The three essential roles of surfactant in the lung.
How surfactant can be displaced from the alveolar lining and the
consequences of this, and how collapsed alveoli can be expanded and
relined with surfactant
The effect of pulmonary fibrosis on lung compliance and the effect this
has on patients' breathing
The origin of infant respiratory distress of the newborn, the effect it has
on infants' lungs and breathing, what sort of infants are most likely to
have the syndrome (and why) and the principles for preventing it.
The structure of the pleural cavity
How we inflate and deflate our lungs
Pneumothorax
Lung compliance
Factors that alter lung compliance
Breathing in is an active process, breathing out (at rest) is just relaxing of these
muscles.
The lungs are not attached to the chest wall, they slip against the chest wall. The lungs
have elastic properties.
, Before inspiration, alveolar pressure is zero (equal to atmospheric). The intrapleural
pressure is negative as the opposing forces of the lungs trying to collapse (recoil) and
chest expand creates the negative space which holds the airways open.
During inspiration, the inspiratory muscles contract and the alveolar pressure (P alv)
becomes LESS than the atmospheric pressure (Patm) which is why air flows in and the
alveoli expand. Because lung volume increases, the elastic recoil strength of the lung
also increases, as a result intrapleural pressure becomes even more negative. At the
peak of quiet inspiration, lung volume is FRC + TV.
The inspiratory capacity (IC) is the maximum volume of gas that can be inhaled from
the end of resting exhalation, it is equal to the sum of tidal and inspiratory reserve
volume.
The inspiratory reserve volume (IRV) is the additional air you can get into the lungs at
the end of normal tidal volume (normal breath)
During expiration, alveolar pressure becomes greater than atmospheric due to being
compressed by the elastic forces of the lung, so air flows down the pressure gradient,
out of the lungs and the alveoli become return to their original size.
The functional residual capacity (FRC) is the volume of air present in the lungs at the
end of passive expiration, at FRC the elastic recoil forces of the lungs and chest wall
are equal but opposite and there is no exertion by diaphragm or other respiratory
muscles
The expiratory reserve volume (ERV) is the additional air that can be forcibly exhaled
after the expiration of a normal tidal volume.
