Gas Transport & Erythrocyte Physiology

Question 1

What are the fxns of erythrocytes?

Answer 1

• deliver oxygen and nutrients
• remove wastes
• maintain homeostasis (acid/base buffering)
• circulation

Question 2

What is the hematocrit (ratio of RBC) in an adult male?

Answer 2

-45 percent

Question 3

What is the hematocrit (ratio of RBC) in an adult female?

Answer 3

-40 percent

Question 4

What is the hematocrit (ratio of RBC) in a 2-month-old infant?

Answer 4

-35 percent

Question 5

What is the hematocrit (ratio of RBC) in a newborn?

Answer 5

-55 percent

Question 6

Delineate the cell stages of erythropoiesis.

Answer 6

Hematopoietic Stem Cell
Reticulocyte
Erythrocyte

Question 7

What is the main influence on erythrocyte maturation?

Answer 7

oxygen demand

Question 8

What hormone is the main regulator of erythrocyte production?

Answer 8

erythropoietin (EPO)

Question 9

Where is erythropoietin (EPO) synthesized?

Answer 9

kidney

Question 10

What situations prompt the synthesis of erythropoietin (EPO)?

Answer 10

• anemia
• low Hb
• low blood volume (particularly RBF)
• central hypoxia

Question 11

What transcription factor is responsible for regulating synthesis of erythropoietin (EPO)?

Answer 11

hypoxia inducible factor (HIF)

Question 12

How long is the life cycle of an erythrocyte?

Answer 12

120 days

Question 13

Where does an erythrocyte go to “die” (aka rupture)?

Answer 13

red pulp of the spleen

Question 14

How does the Hb from a ruptured RBC get “taken up”?

Answer 14

Hb is ingested immediately by macrophages

Question 15

What happens to the heme from a ruptured RBC?

Answer 15

it gets converted and is excreted in the feces

• biliverdin, bilirubin, urobilinogen, stercobilin
• stercobilin makes feces brown

Question 16

What happens to peptides released from ruptured erythrocytes in the spleen?

Answer 16

peptides get broken down into amino acids and are re-used in protein synthesis

Question 17

What happens to the iron released from ruptured erythrocytes in the spleen?

Answer 17

-iron is bound to transferrin and taken to the liver

• stored as ferritin
• shipped to marrow for RBC production

Question 18

What are the ways oxygen is transported in the blood?

Answer 18

• dissolved

- bound to Hb (majority)

Question 19

What are the ways that carbon dioxide is transported in the blood?

Answer 19

• dissolved
• carbamino compounds
• bound to an amine group other than heme
• bicarbonate (majority)

Question 20

What is a Haldane shift?

Answer 20

-the presence of oxygen reduces the affinity of the other amine groups for carbon dioxide

Question 21

What enzyme converts carbon dioxide to bicarbonate plus a hydrogen ion?

Answer 21

carbonic anhydrase

Question 22

What ion helps export dissolved carbon dioxide from the blood?

Answer 22

chloride

Chloride Shift, aka Hamburger Shift

Question 23

What is the approximate volume of oxygen carried in the blood versus carbon dioxide?

Answer 23

20 mL oxygen per 100 mL blood

50 mL carbon dioxide per 100 mL blood

Question 24

What is the major form of oxygen in the blood?

Answer 24

bound to Hb

Question 25

What is the major form of carbon dioxide in the blood?

Answer 25

bicarbonate

Question 26

What is a normal amount of dissolved oxygen in the blood versus carbon dioxide?

Answer 26

0.3 mL oxygen per 100 mL blood | 3 mL carbon dioxide per 100 mL blood

Question 27

What is a normal amt of Hb in the blood?

Answer 27

15 g per 100 mL blood

Question 28

How much oxygen can bind to 1 g of Hb?

Answer 28

1.34 mL

Question 29

What is a normal oxygen concentration in blood?

Answer 29

15 x 1.34 = 20.1 20.1 mL oxygen per 100 mL blood

Question 30

What does a L shift in the oxygen-dissociation curve represent?

Answer 30

-increased affinity of Hb for oxygen

Question 31

What are two conditions associated with a L shift of the oxygen-dissociation curve?

Answer 31

polycythemia | methemoglobinemia

Question 32

What does a R shift in the oxygen-dissociation curve represent?

Answer 32

-decreased affinity of Hb for oxygen

Question 33

What medical condition is associated with a R shift of the oxygen-dissociation curve?

Answer 33

anemia

Question 34

What parameters are increased in a R shift of the oxygen-dissociation curve?

Answer 34

- carbon dioxide - more acidic muslce - BPG - exercise - local temperature, metabolism

Question 35

Why are B12 (cobalamin) and B9 (folate) important for RBC production?

Answer 35

B12 and B9 are req'd for DNA synthesis

Question 36

Why is iron important for RBC production?

Answer 36

iron is req'd for Hb to bind oxygen

Question 37

True or False: erythrocytes have mitochondria

Answer 37

False

Question 38

Why do erythrocytes need ATP?

Answer 38

- ATP is used to maintain iron in the ferrous (Fe2+) state | - w/o ATP, cells are exposed to oxidative damage

Question 39

How does iron-deficient anemia impact the oxygen-carrying capacity of blood?

Answer 39

-less Hb = less oxygen content - 15 g x 1.34 = 20.1 mL oxygen per 100 mL blood - 8 g x 1.34 = 10.72 mL oxygen per 100 mL blood

Question 40

What does percent saturation indicate when referring to Hb and oxygen?

Answer 40

- what percentage of the Hb's are bound to an oxygen | - thus, oxygen content of the blood can decrease d/t less Hb, while percent saturation doesn't change!

Question 41

What is hemochromatosis?

Answer 41

iron overload

Question 42

What are some causes of hemochromatosis?

Answer 42

- neonatal (unknown cause develops in utero) - primary (genetic) -secondary (multiple blood transfusions, increased iron intake, ineffective erythropoiesis)

Question 43

What are some characteristics of primary polycythemia (genetic)?

Answer 43

- low EPO - extra RBC's - increased blood volume - increased viscosity - normal-ish cardiac output

Question 44

What are some characteristics of secondary polycythemia?

Answer 44

- causes: hypoxia, neoplasms, cancer, kidney disease - increased EPO - extra RBC's - abnormal cardiac output

Question 45

What are some characteristics of physiologic polycythemia?

Answer 45

- high altitude adaptation - extra RBC's - normal cardiac output

Question 46

What are the characteristics of methemoglobinemia?

Answer 46

- increased met-Hb - iron is in the ferric (Fe3+) form - decreased oxygen availability to tissues - chocolate-colored blood - blue skin

Question 47

What is the equation to calculate arteriovenous (a-v) oxygen difference?

Answer 47

PaO2 going into a tissue minus PvO2 coming out of a tissue

Question 48

What is the arteriovenous oxygen difference used for?

Answer 48

-indicates oxygen consumption in a certain tissue

Question 49

What situations could have an increased arteriovenous oxygen difference?

Answer 49

- exercise | - certain tissue types such as the kidney

Question 50

What does the respiratory quotient describe?

Answer 50

the relationship b/w amt of oxygen consumed and carbon dioxide produced

Question 51

What factor changes the respiratory quotient?

Answer 51

the type of fuel being used by the body - glucose = 1.0 - mixed fuels = 0.8

Question 52

What situations would cause the respiratory quotient to increase?

Answer 52

exercise