Respiration 2 Flashcards
State Daltons Law
Total pressure = sum of partial pressures
P= pN2 +pO2+pCO2+pH20
What is the partial pressure of a gas?
Pressure the gas would exert if it was the only gas present
What is the make up of the air?
Nitrogen 78%
Oxygen 21%
What is the relationship between Alveolar ventilation and alveolar pp of O2?
As ventilation increases the pp of O2 increases
curve upwards and level off
What is the relationship between Alveolar ventilation and alveolar pp of CO2?
As ventilation increases , pp of CO2 decreases (sharp downwards curve then level off)
State Fixs Law
Diffusion coefficent= K solubility (x) / square root of Mwt(x)
t= respiratory membrane
A= area for diffusion
P=chnages in pp
What is the rate limiting step in the movement of gases into solution ?
The rate at which the gases dissolve into the tissue water
What are 5 parts of the respiratory membrane?
Alveolar epithelium
Epithelial basement membrane
Capillary basement membrane
Capillary ENdothelium
What is the average diameter of the pulmonary capillaries
~ 5 mm
What is the distance between the alveolar space and capillary lumen?
1-2um and this is covered in about 1ms by O2
Which has higher pp in O2 and CO2?
Pulmonary Arterioles or Pulmonary venules
O2= Pulmonary Ventricles Co2= Pulmonary Arterioles
How long does it take for blood to equilibrate with alveolar gases in the normal lung?
<0.2 sec
What is perfusion?
Blood flow
During exercise the blood flow increases, why is this advantageous?
Time in capillary reduces so increased movement of CO2 and O2
Also increased pulmonary arterial pressure which causes closed vessels to open and vessels to dialate
What are the 2 physiological regulated factors determined O2/Co2 transfers between alveolus and tissue?
rate of alveolar ventilation
Blood flow
In the higher part of the lung which is higher
rate of alveolar ventilation or blood flow
rate of alveolar ventilation
In the lower part of the lung which is higher
rate of alveolar ventilation or blood flow
Blood flow
State the equation used to find alveolar ventilation
V= (V Tidal-V dead) x resp.rate
What is the ans to rate of alveolar ventilation/ Blood flow
about 0.8
What is hypoxic vasoconstriction?
When PO2 within the alveoli decreases there is a decrease in blood flow to the alveolus
What is the result of hypoxic vasoconstriction?
O2-sensitive K+ channels in the smooth muscle membrane of the pulmonary arterioles. At low O2 the K+ channels close, the cell depolarizes and contracts, so these arterioles partially close.
Why is hypoxic vasoconstriction important?
Important in the pulmonary circulation helping to match perfusion with ventilation
What happens when there is a blockage of one alveolar region?
Decreased tissue PCo2 around an underventilated alveoli constricts their atriers diverting blood to better ventilated alveoli
Define Anatomical DS
The volume of respiratory tract involved in conducting gas not in transfer to blood
