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How big is the gas exchange area?

70 m^2


what is the alveolar capillary diffusion distance?

0.4 micrometers


Where does respiration occur?



What are the 3 different kinds of dead space VD?

1. anatomic dead space
2. alveolar dead space
3. physiological dead space


alveolar dead space

the volume of inspired air that is delivered to alveoli in which there is no gas exchange or gas exchange is incomplete


anatomic dead space

volume of all non-gas exchange airways from the nose (or mouth, during mouth breathing) down to the respiratory bronchioles


physiologic dead space

the sum of anatomic dead space and alveolar dead space

*defines the portion of each inspiration that does not participate in gas exchange


why is alveolar ventilation less than pulmonary ventilation?

less because of anatomical dead space


What is convection?

convection is the bulk movement of gas due to pressure gradients and requires mechanical power input


What two transport processes occur by means of convection?

1. transport from the environment to terminal bronchioles
2. transport of erythrocytes between pulmonary capillaries and peripheral capillaries


what is diffusion?

transport based on random motion of thermally energetic particles situated in a concentration gradient


What transport processes occur by means of convection?

1. transport between terminal bronchioles to erythrocytes
2. transport between erythrocytes and peripheral mitochondria


Whats the difference between convection and diffusion?

in convection, gas moves from high pressure to low pressure. In diffusion, there is no pressure or mechanical movement


the movement of particles by convection is driven by what?

the pressure gradient between the atmosphere and terminal bronchioles


The mechanical work required for convection is a function of what 3 factors?

1. resistance of the transport path to air flow (diameter and cross-sectional area of airways)
2. the viscosity and density of air being moved
3. the compliance of the lung and chest wall


The movement of particles by diffusion is driven by what two factors?

1. concentration gradient
2. diffusivity


What is diffusivity?

a measure of the tendency of a molecule to avoid getting hung up in the surrounding media, specific for solute, solvent, temperature.


dalton's law

the total pressure of a gas mixture is the sum of the partial pressures of its constituents


henry's law

the partial pressure of a gas in equilibrium with a volume of liquid is proportional to the amount of gas dissolved in the liquid


k = constant
c = [ ] of the gas


partial pressure

the pressure exerted by each type of gas in a mixture


What determines the concentration of a gas in a liquid

1. partial pressure
2. diffusivity (solubility coefficient)


How do gases dissolve in fluids?

by moving down a partial pressure gradient rather than a concentration gradient


what is the partial pressure of oxygen and carbon dioxide in the pulmonary artery?

oxygen: 40 mmHg
carbon dioxide: 46 mmHg


what is the partial pressure of oxygen and carbon dioxide in the lungs?

oxygen: 105 mmHg
carbon dioxide: 40 mmHg


what is the partial pressure of oxygen and carbon dioxide in the pulmonary vein?

oxygen: 100 mmHg
carbon dioxide: 40 mmHg


what is the A-a gradient?

alveoli - artery gradient

It is the difference between oxygen content in alveolus gas (measured during exhalation) and the oxygen content in arterial blood (equivalent to that leaving the lungs)


what is abnormal A-a?

~10 mmHg


What are the factors contributing to the A - a gradient?

1. blood shunts
2. blood mixing
3. matching


what 3 things does gas diffusion in the lung depend on?

1. area of the respiratory membrane
2. distance of the diffusion
3. V/Q (ventilation and perfusion)


what is pulmonary diffusion capacity?

the ability of the respiratory membrane to exchange a gas between the alveoli and the pulmonary blood.

defined as the volume of gas that diffuses through the membrane each minute for a pressure of 1 mmHg.

DL = V/Pa-Pc