Gas Transport and Erythrocyte Physiology

Question 1

How long is the erythrocyte life cycle?

Answer 1

120 days

Question 2

Where does erythrocyte breakdown occur?

Answer 2

Macrophages of the spleen, liver, or red bone marrow

Question 3

What regulates erythropoiesis?

Answer 3

Erythropoietin produced by the kidneys in response to anemia, low hemoglobin, decreased RBF, or hypoxia

Question 4

What regulates release of erythropoietin?

Answer 4

Hypoxia inducible factor

Question 5

How is oxygen transported in the blood?

Answer 5

Bound to hemoglobin or dissolved

Question 6

What is the typical form of hemoglobin for an adult?

Answer 6

HbA containing two alpha chains and two beta chains

Question 7

What is the hemoglobin for a fetus?

Answer 7

HbF, contains two alpha chains and two gamma chains which gives it higher affinity for oxygen

Question 8

Doe oxygen bind ferrous or ferric iron in hemoglobin?

Answer 8

Ferrous

Question 9

How is CO2 transported in the blood?

Answer 9

5% dissolved, 5% bound to hemoglobin, 90% as bicarb

Question 10

What directly forms bicarbonate?

Answer 10

Directly from CO2 and OH or CO3 2- and H by carbonic anhydrase

Question 11

How does CO2 enter the cell?

Answer 11

AQP1

Question 12

How does bicarb enter the cell?

Answer 12

Depends on carbonic anhydrase Bicarb chloride exchanger and Hb

Question 13

What happens with carbon dioxide and bicarbonate within the lungs?

Answer 13

CO2 dissociates from the proteins and bicarb is converted back into CO2 and then it is exhaled

Question 14

What is considered the normal hb concentration in the blood

Answer 14

15 g/100 mL

Question 15

According to the oxygen hemoglobin dissociation curve, at 97.5% hb saturation, what should total oxygen in arterial blood be?

Answer 15

19.9 so roughly 20 mL O2/100 mL blood

Question 16

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?

Answer 16

15.2 ml O2/ 100 mL blood on venous side

Question 17

What will cause a right shift in the ox-hb dissociation curve? What clinical conditions is associated with this?

Answer 17

• 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

Question 18

What conditions can cause a left shift in the ox hb dissociation curve?

Answer 18

• Methemoglobinemia
• HbF
• Polycythemia
• Decreased temp
• Increased pH
• Ddecreased PCO2

Question 19

What does it mean to “shift left” on the ox-hb dissociation curve?

Answer 19

• Indicates a higher affinity of Hb for O2
• This means we hold onto oxygen better

Question 20

What is the significance of CO?

Answer 20

• 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