Gas Transport and Erythrocyte Physiology Flashcards
How long is the erythrocyte life cycle?
120 days
Where does erythrocyte breakdown occur?
Macrophages of the spleen, liver, or red bone marrow
What regulates erythropoiesis?
Erythropoietin produced by the kidneys in response to anemia, low hemoglobin, decreased RBF, or hypoxia
What regulates release of erythropoietin?
Hypoxia inducible factor
How is oxygen transported in the blood?
Bound to hemoglobin or dissolved
What is the typical form of hemoglobin for an adult?
HbA containing two alpha chains and two beta chains
What is the hemoglobin for a fetus?
HbF, contains two alpha chains and two gamma chains which gives it higher affinity for oxygen
Doe oxygen bind ferrous or ferric iron in hemoglobin?
Ferrous
How is CO2 transported in the blood?
5% dissolved, 5% bound to hemoglobin, 90% as bicarb
What directly forms bicarbonate?
Directly from CO2 and OH or CO3 2- and H by carbonic anhydrase
How does CO2 enter the cell?
AQP1
How does bicarb enter the cell?
Depends on carbonic anhydrase Bicarb chloride exchanger and Hb
What happens with carbon dioxide and bicarbonate within the lungs?
CO2 dissociates from the proteins and bicarb is converted back into CO2 and then it is exhaled
What is considered the normal hb concentration in the blood
15 g/100 mL
According to the oxygen hemoglobin dissociation curve, at 97.5% hb saturation, what should total oxygen in arterial blood be?
19.9 so roughly 20 mL O2/100 mL blood
According to the oxygen hemoglobin dissociation curve on the venous side, if we are at 75% saturation what will the total oxygen in the blood be?
15.2 ml O2/ 100 mL blood on venous side
What will cause a right shift in the ox-hb dissociation curve? What clinical conditions is associated with this?
- Increased Pco2 as carbon dioxide decreases hb affinity for oxygen, this is advantageous for unloading oxygen quicker
- Increased temperature
- Decreased pH (or higher H concentration)
-
Increased 2,3-BPG this is a biproduct of glycolysis which is increased by low Po2, seen with chronic hypoxia or anemia
- the largest effect is on venous/tissue side of curve
- Associated with anemia
What conditions can cause a left shift in the ox hb dissociation curve?
- Methemoglobinemia
- HbF
- Polycythemia
- Decreased temp
- Increased pH
- Ddecreased PCO2
What does it mean to “shift left” on the ox-hb dissociation curve?
- Indicates a higher affinity of Hb for O2
- This means we hold onto oxygen better
What is the significance of CO?
- CO displaces oxygen from a fully saturated Hb molecule reducing the binding capacity for oxygen molecules
- It causes a significant left shift in the curve resuting in less oxygen delivery to tissues
- Sx include headache, N/V, can cause death if not caught
