McArdle ch. 13/ Guyton ch.40 Flashcards
what is the ventilation perfusion ratio=?
Va/Q
Va=alveolar ventilation rate
Q= rate of pulmonary blood flow
Explain the concept of physiologic dead space
has sufficient Va(air) but Q(cardiac output)
the way how i think of it is that: the physiologic dead space is at the top of the lungs where the blood is sent at the bottom of the lungs so theres enough air but no blood to do the exchange with
explain the concept of physiologic shunt
when Va/Q is below normal since theres an inadequate amount of Va(air) bc all the blood is sent at the bottom of the lungs theres little air but lots of blood so low ventilation perfusion.
def: certain fraction of venous blood passes though pulmonary capillaries without getting oxygenated.
the greater the physiologic shunt the ____ the amount of blood that fails to be oxygenated as it passes through the lungs
greater
explain how in different areas in the lungs are different when it comes to the ventilation perfusion ratio
at the top of the lungs: VA/Q is 2.5x greater that as the ideal value = physiological dead space (i.e. more alveoli are being ventilated than perfused)
at the bottom of the lungs:there is too little ventilation in relation to blood flow, VA/Q is as low as 0.6x the ideal value. In this area, a small fraction of the blood fails to become normally oxygenated = physiological shunt
During exercise:Better blood flow to the top of the lung = physiological dead space is ____
decreased
since theres more blood flow so more blood getting to the top of the lungs
what does the bodys supply of oxygen depend on?
- Concentration of ambient air
20. 9% O2, 78.6% N2, 0.04% CO2 - Pressure of ambient air
Once alveoli are ventilated with fresh air, next step in respiratory process is ____ of O2 from alveoli into pulmonary blood and diffusion of CO2 in opposite direction
diffusion
what is diffusion?
random motion of molecules
gas pressures are caused by?
Caused by impacts of moving molecules against surface
what is the relationship with impacts of gas molecules and pressure
More impacts = higher pressure
what is the relationship with the movement of gas molecules and pressure?
The faster the movement, the higher the pressure
what is the pressure caused by each gas alone?
partial pressure(Px) ex: PO2, PN2,...
Diffusion rate of each gas is _____ proportional to its partial pressure gradient (concentration)
directly
what is Total gas pressure?(daltons law)
a mixture of gases (Ptot) equals the sum of the partial pressures of all gases
Dalton’s Law: Ptot = PO2 + PN2 + PCO2 + Pother
what is the air pressure at sea level?
760 mmHg
Gas dissolved in water and tissues exerts its own ___ ___ on surface of membrane in same way as gas does in gas phase
partial pressure
what is partial pressure of a dissolved gas determined by? (2)
concentration and solubility
what the partial pressure equation?
PP= [dissolved gas]/ solubility coefficient
what is henry’s law?
The mass of a gas
that dissolves in a fluid at a given temperature varies in direct proportion to the pressure of the gas over the liquid
what are the factors that govern the rate of gas diffusion into a fluid?
- The pressure differential between the gas above the fluid and the gas dissolved in the fluid
- The solubility of the gas in the fluid.
explain the solubility coefficient:
- Measure of electro-chemical attraction that a dissolved gas has to water molecules
- High attraction = high solubility of gas, i.e more gas molecules can be dissolved before partial pressure of that gas within the solution increases
what is the difference between CO2 and O2 solubility?
CO2 is 24 times more soluble than O2 in fluid
O2: 0.024
Co2:0.57
what are the factors that affect the diffusion rate through a respiration membrane?
D proportional to:
change in P* cross sectional area * solubility / distance * sqrt(molecular weight)