5.4 Flashcards
how does gas exchange occur
by difussion
rate of diffusion across the lungs is:
- proportional o partial pressure gradient
- proportional to the available surface area
- inversely proportional to the thickness of the membranes
- over the short distances
partial pressure gradient influenced by:
and how are they affected
- composition of inspired air
- affected by altitude - Alveolar ventilation
- can be affected by :
- - changes in airway resistance - eg asthma
– changes in lung compliance - fibrosis
how are gasses transported throught the body
they dissolve in plasma or in the RBCs
how is tthe solubility of oxygen in plasma and how is it transported
low solubility in plasma
- most o2 is transported by RBC (erythrocytems) - whithin RBCs O2 is bound by haemoglobin
how many oxyegn molecules can each hemogoblin molecule bind to
up to 4 oxygen molecules
how do oxygen bind twith iron in haeme group
reversibly
what is hemoglobin bound to oxygen
oxyhaemoglobin (HbO2)
what is unbound heamoglobin
deoxyhemoglobin
what percent of saturation of heamoblobin
% of available binding sites that are bound to oxygen
how is carbon dioxide trnsported
3 mechanisms
- dissolved in plasma
- interact with protiens
- convert to bicarbonate
how does carbon dissolve in plasma and what it do
CO2 is more soluble in body fluids than oxygen; however, cells produce more CO2 than can be carreid in plasma, more CO2 b/c more soluble
how does CO2 interact with protiens
including heaemoglobin via 4 termnal amine groups on the protien
- forms carbaminohaemoglobins
- deoxy-heamoglobin interact more readily with CO2 than oxy-haemoglobin
how does CO2 to bicarbonate
the majority of CO2 entering the blood is converted by reaction catalyzed by carbonic anhydrase (resent in RBCs) - the H+ formed by this reaction binds to Hb
The bicarbonate ions are moved out of the RBC by a transpoter protein which exchanges HCO3- for Cl- in a process is known as the chloride shift
when venous blood reaches lungs what happens
the PCO2 of alveoli is lower than blood
- CO2 dissolves in plasma diffuses into alveoli and then CO2 in RBC diffuses into plasma
and the equilibrium of CO2- bicarbonate reaction is shifted
