Gas exchange and ventilation Flashcards
What happens to upper respiratory tract when inhalation
Tends to constrict when air is drawn into the lungs
What happens to lower respiratory tract when inhalation
expands when air is drawn into the lungs
Alveolar pressure
pressure inside the alveoli relative to atmospheric pressure
Intrapleural pressure
pressure between the pleural membranes
transmural pressure
Alveolar pressure MINUS intrapleural pressure
What happens in Inhalation
Intercostal muscles contract
Ribcage is raised
Diaphragm muscles contracts and flattens
volume of thoracic cavity increases
lungs are pulled open
air is pulled into lungs through trachea
What happens in exhalation
intercostal muscles contract
ribcage falls
diaphragm muscles relaxes and domed shape
volume of thoracic cavity decreases
lungs are compressed
expired gas flows out through trachea
What is Lung compliance
Measure of stretchiness of the lung
High lung compliance
very stretchy so a small amount of pressure results in a large increase in volume (easy to inflate)
Low lung compliance
Not very stretchy so a large amount of pressure required to increase in volume (difficult to inflate)
How does Surface tension and alveoli interact
watery lining on inner surface of alveoli Water molecules attract to each other in alveoli and gives a pull towards centre of alveolus causing alveoli difficult to inflate
Surfactant interact with alveoli
Some alveolar cells produce surfactant that surfactant sit on surface of watery lining so reduces ability for water molecules to attract each other reducing pull towards centre and meaning alveoli are easier to inflate
Tidal volume
Volume of air in a normal breath
residual volume
volume of air in lungs after maximum forceful expiration
Vital capacity
Maximum volume of air can be expelled from lungs after a maximum inhalation
Total lung capacity
The volume of air at maximum inflation
Typical total lung volume human 75kg
6L
Typical tidal volume human 75kg
0.5L
Typical total lung volume mouse 0.035kg
0.001L
Typical tidal volume mouse 0.035kg
0.0005L
Typical total lung volume dog 20kg
2.2L
Typical tidal volume dog 20kg
0.25L
Typical total lung volume horse 500kg
55L
Typical tidal volume horse 500kg
5L
How to find total lung volume from body mass
~~~divide by 10
How to find tidal volume from body mass
~~~divide by 100
Factors affecting gas exchange
alveolar surface area
thin aveolar barrier
high blood flow
fluid film inside aveoli
regular refilling with fresh air
How does alveolar surface area effect diffusion
increase rate of diffusion
How does alveolar barrier effect diddusion
increase rate of diffusion
how does high blood flow effect diffusion
increase rate of diffusion as low 02/high C02 removed so concentration gradient maintained
how does fluid film inside alveoli effect diffusion
increase rate of C02 diffusion as can dissolve in fluid
How does regular refilling with fresh air effect diffusion
increases rate of diffusion by maintaining concentration gradients
What part of the brain controls ventilation and how
medulla and chemoreceptors detect low P02/ high PC02 or vice versa and either increase or decrease intercostal muscles/diaphragm rate respectively
What intercostal muscles for inspiration
innner
What intercostal muscles for expiration
external
how to calculate transmural pressure
alveolar - intrapleural pressure
What happens to the 2 pressures when inspiration
alveolar decreases and intrapleural decreases further
Describe/draw graph of tidal volume
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Describe/draw graph of intrapleural pressure
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Describe/draw graph of airflow
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Describe/draw graph of alveolar pressure
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How to calculate Ventilation( L min^-1)
Tidal volume(l) x Respiratory rate ( breaths min^-1)
What is oxygen consumption
Oxygen is used by most cells in body to release energy. The volume of oxygen consumed by an animal per minute reflects metabolic rate and is expressed relative to body weight of animal so comparisons can be made. e.g. racehorses
How to calculate volume of OXYGEN consumed
Subtract volume exhaled of oxygen from inhaled volume of oxygen
How to calculate oxygen consumption/V02 max
(frac Conc oxygen inhaled air (FiO2) - frac conc oxygen exhaled air (FeO2) x Ventilation(volume inhaled and exhaled) ) divide by body mass
How to calculate V02 max (L min^-1 kg^-1) equation
((FiO2 - FeO2) x V)/ body mass
