regulation of erythropoiesis

Question 1

what’s the importance of regulation of RBCs count in circulation in narrow range ?

Answer 1

1. sufficient number of RBCs are always available to supply adequate transport of O2 from the lung to tissues
2. the RBCs don’t become so numerous that they block the blood flow

Question 2

…….. is the most important regulator of erythropoiesis

Answer 2

tissue oxygenation

Question 3

condition that produce ………. increase the rate of RBCs production

Answer 3

hypoxia ( decrease O2 delivery to the tissue )

Question 4

how hypoxia increase the rate of RBCs production ?

Answer 4

hypoxia stimulate erythropoiesis by stimulating the secretion of erythropoietin hormone which in turn stimulates erythropoiesis in red bone marrow

Question 5

factor that dec the oxygenation

Answer 5

1. low blood volume
2. low Hb
3. anemia
4. poor blood flow
5. pulmonary dis

Question 6

illustrate the composition of the erythropoietin hormone

Answer 6

• it’s glycoprotein , present in plasma in low con .
• in adult : 85-90% from kidney
  10-15% from liver

Question 7

the half life of erythropoietin hormone about ……….

Answer 7

5 hours

Question 8

illustrate the functions of erythropoietin hormone

Answer 8

1. it stimulates the production of proerythroblast from erythropoietin sensitive comitted stem cells.
2. it inc the speed of conversion of one step to another in erythroblastic stages

Question 9

list factors stimulating erythropoietin secretion

Answer 9

1. hypoxia ( also cobalt salt has the same role ) : inc tissue levels of hypoxia inducible factor-1 (HIF-1) which act as transcription factor for erythropoietin gene
2. hormone : androgen , catecholamine , corticosteroid , GH hormone and thyroxin inc erythropoietin secretion
3. alkalosis as in high altitudes

Question 10

in ……….the stem cell don’t respond to erythropoietin

Answer 10

aplastic anemia

Question 11

renal faliure is associated with anemia that can be treated only with ….

Answer 11

erythropoietin

Question 12

list requirements of erythropoiesis

Answer 12

1. dietary substances :
   -protein
   - iron
   - vit b12 and folic acid ( maturation factor)
   their deficiency appear as megaloblastic or macrocytic anemia
   - other trace element as copper and cobalt
2. hormones :
   stimulate = androgen
   inhibit= estrogen
3. normal functioning bone marrow
4. nomal functioning kidney
5. normal functioning liver

Question 13

what is the fate of RBCs ?

Answer 13

taken up by RES, Hb molecule is broken into heme and globin :
-heme: loses its iron which stored and reused for Hb synthesis
the rest converted into bile pigment ( bilirubin or biliverdin ) excreted with bile by liver
- globin : broken down into A.A , which join to metabolic pool