respiratory 3 Flashcards
O2 and CO2 gas exchange occurs solely by
diffusion
henry’s law
when a mixture of gases is in contact wth a liquid, each gas will dissolve in the liquid in proportion to its partial pressure
at equlibrium - partial pressures in alveoli and capillaries will be equal
diffusion rate depends on
- surface area
- concentration (P) gradient
- thickness of the membrane
- diffusion constant (solubility, molecular weight)
exercise decreases
time available for diffusion
limitations to pulmonary gas exchange
- low inspired oxygen
- hypoventilation
- diffusion limitations
- ventilation-perfusion mismatching
ventilation perfusion coupling
lungs and blood flow to the lungs trying to match each other
V/Q ration
VENTILATION
THE AIR REACHING THE ALVEOLI
perfusion
the blood reaching the alveoli
impaired ventilation
shunt
impaired perfusion
dead space
when theres not enough ventilation
the bronchioles dilate and the pulmonary arterioles constrict
when theres not enough perfusion
the pulmonary arterioles dilate and the bronchioles constrict
shunts
venous blood going through the lungs without being oxygenated
0 ventilation perfusion ratio
dead space
ventilated alveoli don’t receive blood
infinite ventilation perfusion ratio
regional differences in perfusion pressure
perfusion pressure is greater lower down in the lungs
bottom is over perfused and the top is under perfused
if you have a cancer at the bottom of your lungs
you’ll be under perfused overall because the bottom is over perfused
high V/Q
usually pulmonary embolism
low V/Q
chronic bronchitis, asthma, pulmonary oedema
blood pO2
100mmHg at lungs and 40mmHg after circulating
carbamino
CO2 combines with terminal amino groups of proteins (haemoglobin)
CO2 and O2 bind seperate parts of haemoglobin
bicarbonate
most CO2 in blood is carried as bicarbonate
3 ways CO2 is transported
- dissolved in blood
- carbamino
- bicarbonate
most CO2 is transported as
bicarbonate
carbonic anhydrase
converts carbon dioxide to bicarbonate
