Gas Transport in the Blood Flashcards
What do erythrocytes do?
maxmises the surface area to volume ration, 1/3 of RBC made up of haemoglobin
what are haemoglobin molecules made up of?
4 polypeptides called globins , each bind one heme molecules
What does each heme molecule have?
a red colour and binds one iron molecules
What molecule bind oxygen?
iron molecules
What does adult haemoglobin have?
2 alpha chains and 2 beta chains
What is oxygen rich haemoglobin called?
Oxyhaemoglobin
What is oxygen defficient haemoglobin?
Deoxyhaemoglobin
What is lifespan of erythrocytes?
M 120days F 110 days
How long does erythropoiesis take?
takes 4 days and occurs in bone marrow
What stimulates erythropoiesis?
low PO2 increases formation of glycoprotein erythropoeitin in the kidney, induces bone marrow to make more erythrocytes
What are 3 factors of transport respiratory gases?
Oxygen diffusion gradients
Carbon dioxide diffusion gradients
Haemoglobins oxygen disassociation relationship
What is po2 in alveoli and capillary?
104mmhg, po2 in alveolar capillaries is 40mmhg - o2 diffuses following its po2 into blood untill 104mmhg
What does blood leaving the alveolar capillaries have a po2 of?
104mm, by the time reaches pulmonary vein will be 95mm -pulmonary vein recieves some deoxygenated blood from bronchial veins - transported to tissues
What will interstitial fluid have a po2 of?
40mmhg and cells 20mmhg - oxygen flow from the blood capillaries into the interstitial fluid and then into cells
what do cells produce and why?
CO2 and results in intracellular pco2 of 46mmHg but intersitital fluid has a PCO2 of 45mm hg and capillaries supplying the tissues with blood will have PCO2 of 40mm Hg
Where does CO2 diffuse into?
blood so that by the time deoxygenated blood pumped back to lungs through pulmonary artery it has a PCO2 of 45mmHg
What is PCO2 of alveoli?
40mmHg so CO2 diffuses from blood into alveoli - blood passes into pulmonary vein now a PCO2 of 40mmHg
How much oxygen does haemoglobin carry?
87% in oxygen and 3% in solution of blood plasma. the binding of 02 with haemoglobin is reversible - o2 binds to haemoglobin in lungs disassociates from haemoglobin in the tissues - relationsip described by oxygen disassociation curve
When is haemoglobin in erythrocytes 100% saturated with oxygen?
Po2 of 80mmHg and above the blood in alveolar capillaries is saturated
What is the PO2 of blood in capillaries?
Of tissues is 40mmHg and at PO2 40mm haemoglobin is 75% saturated and 25% of o2 carried to disassociate into the interstitial fluid
During exercise the PO2 of interstitial fluid is what?
In skeletal muscle drop to 15mmHg and at PO2 haemoglobin gives up 75% of its o2
When does haemoglobin decline?
with decreasing PH when haemoglobin bind O2 at ny PO2
What is an Decrease in PH caused by?
increase in concentration of hydrogen ions
How is carbonic acid formed?
as PCO2 increases CO2 combines with water to form.
What does carbonic acid disassociate into?
carbonic acid disassociates into H and bicarbonate ions
What do hydrogen ions bind to?
Protein part of haemoglobin molecule causing a comformational change decreasing the affinity of haemoglobin for O2
What does a decrease in PH cause?
an increasing in the CO2 concentration means a greater PO2 is needed to saturate the haemoglobin - curve shifts to the right
What causes oxygen curve to the right?
Increases in temperature as accumulation of acidic products such as lactic acid
What happens in heavy exercise?
CO2 and lactic acid accumulate in tissue and temp increases so 85% of o2 released from haemoglobin
IN lungs what happens with increased RR?
PCO2 decreases oxygen curve to left so haemoglobin saturates
What modifies affinity of haemoglobin for O2?
BPG - produced by erythrocytes and decreases the affinity of haemoglobin for 02 - people in high altitudes have high conc of BPG in the blood and increases oxygen delivery to tissues at high altitudes - BPH levels in stored blood decrease with time
How is CO2 transported in blood?
As CO2 in plasma, combined with blood proteins and in form of bicarbonate ions
What are blood proteins that bind CO2 called?
Carbamino compounds - CO2 binds to form carbaminoheamoglobin- the affinity of haemoglobin for CO2 is greate if haemoglobin gives up oxygen this is haldane effect in tissue giving up O2 binds to CO2 in alveoli its opposite
How does CO2 form carbonic acid?
Diffuses into erythrocytes and reacts with water
Where does negative bicarb ions diffuse?
Out of erythrocytes into blood plasma as a result negative cholride ions move into erythrocytes - maintains electrical balance between in and out of cell
What is chloride shift?
Exchange of negative chloride ions for negative bicarb ions
What happens to hydrogen ions that diffuse out of erythrocytes?
PH of plasma would drop and prevented by most hydrogen ion binding
When deoxygenated blood reaches alveoli what happens?
CO2 in blood diffuses into alveoli and co2 to blood proteins go to alveoli - pco2 blood decreases bicarb bck in erythrocytes and haemoglobin releases hydrogen ions - cholirde ions move out of erythrocytes
What causes blood ph increase?
Movement of hydrogen ions into erythrocytes and increaseuptake of oxygen by haemoglobin
