resp physiology Flashcards
what is internal respiration
the intracellular mechanism which consumes O2 and produces CO2
what is external respiration
sequence of events that lead to the exchange of O2 and CO2 between the external environment and the cells of our body
4 steps of external respiration
ventilation
gas exchange
gas transport in blood
gas exchange
what is ventilation
the mechanical process of moving air between the atmosphere and alveolar sacs
what are the forces keeping the alveoli open
- transmural pressure gradient
- pulmonary surfactant
- alveolar interdependence
what are the elastic forces promoting alveolar collapse
- elastic recoil of lungs and chest wall
- alveolar surface tension
describe intra-alveolar pressure and atmospheric pressure
they are the same
- however the intra-pleural pressure is slightly less
what is something that can abolish transmural pressure gradient
a pneumothorax
- this is due to how Air enters the pleural space from outside or from the lungs
The intra-alveolar pressure must become less than atmospheric pressure for air to flow into the lungs during inspiration. How is this achieved?
the lungs expand during inspiration and this makes the intra-alveolar pressure fall and become less that atmospheric
- this is explained by Boyles law (as the volume of a gas increases the pressure decreases)
major inspiratory muscle
diaphragm
external intercostal muscle
expiratory muscles
Abdominal muscles and
internal intercostal muscles
What causes the lungs to recoil during expiration?
Elastic connective tissue in the lungs
alveolar surface tension
describe alveolar surface tension
Attraction between water molecules at liquid air interface
In the alveoli this produces a force which resists the stretching of the lungs
If the alveoli were lined with water alone the surface tension would be too strong so the alveoli would collapse
It lowers alveolar surface tension by interspersing between the water molecules lining the alveoli
accessory muscles of inspiration
Sternocleidomastoid, scalenus, pectoral
tidal volume
Volume of air entering or leaving lungs during a single breath
inspiratory reserve volume
Extra volume of air that can be maximally inspired over and above the typical resting tidal volume
expiratory reserve volume
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
residual volume
Minimum volume of air remaining in the lungs even after a maximal expiration
inspiratory capacity
Maximum volume of air that can be inspired at the end of a normal quiet expiration
(IC =IRV + TV)
functional residual capacity
Volume of air in lungs at end of normal passive expiration (FRC = ERV + RV)
total lung capacity
Total volume of air the lungs can hold
(TLC = VC + RV)
vital capacity
Maximum volume of air that can be moved out during a single breath following a maximal inspiration (VC = IRV + TV + ERV)
what is the Primary determinant of airway resistance
the radius of the conducting airway
Parasympathetic stimulation causes
bronchoconstriction
Sympathetic stimulation causes
bronchodilatation
what is compliance
a measure of effort that has to go into stretching or distending the lungs
- change in lung volume per unit change in transmural pressure gradient across the lung wall (i.e difference between intra-alveolar and intrapleural pressure)
- The less compliant the lungs are, the more work is required to produce a given degree of inflation
decreased compliance may cause
a restrive pattern
when may compliance be abnormally increases
if the elastic recoil of the lungs is lost
eg emphysema
pulmonary ventilation =
tidal volume x resp rate
why is alveolar ventilation less that pulmonary ventilation
due to anatomical dead space
- this is where there is good perfusion but poor ventilation
Alveolar Ventilation =
(Tidal Volume – Dead Space) x Respiratory Rate
what does the transfer of gases between the body and atmosphere depend on
ventilation and perfusion
alveolar dead space =
Ventilated alveoli which are not adequately perfused with blood
the physiological dead space =
the anatomical dead space + the alveolar dead space
factors affecting the rate of gas exchange across alveolar membrane
- Partial Pressure Gradient of O2 and CO2
- Diffusion Coefficient for O2 and CO2
- Surface Area of Alveolar Membrane
- Thickness of Alveolar Membrane
what is the partial pressure of a gas
The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature.
the diffusion coefficient for CO2 is
20x more than for O2
what do Type I alveolar cells do
line the alveoli
