Erythropoiesis - MHSCs, Growth Inducers & Differentiation Inducers

Question 1

What is the cell type in the bone marrow that gives rise to all the cells in the circulating blood?

Answer 1

Multi potential Hematopoietic Stem Cells

Question 2

What are the 2 types of divisions that PHSCs/MHSCs undergo?

Answer 2

1) self-renewing divisions

2) differentiating divisions

Question 3

What is the purpose of self-renewing division f PHSCs/MHSCs?

Answer 3

Maintaining the supply of these stem cells in the bone marrow (although their numbers diminish with age)

Question 4

What are ‘committed stem cells’?

Answer 4

Intermediate stage cells that are very similar to MHSCs.

They have become committed to a particular line of cells.

Question 5

Name the types of cells found during the differentiation of MHSCs to erythrocytes.

Answer 5

MHSC (Multipotential Hematopoietic Stem Cell) 
⬇️ 
CFU-S (Colony-forming-unit - Spleen) 
⬇️
CFU-B (Colony-forming-unit - Blast) 
⬇️
CFU - E (Colony-forming-unit - erythrocytes) 
⬇️
Erythrocytes

(Figure 33-2)

Question 6

What are the 3 types of colony-forming-units that a CFU-S may differentiate into?

Answer 6

CFU-B(Colony-forming-unit-blast)
CFU-GM (Colony-forming-unit- granulocytes, monocytes)
CFU-M (Colony-forming-unit - megakaryotes)

(Figure 33-2)

Question 7

CFU-GMs form different types of cells. What are they?

Answer 7

1. Granulocytes
   
   • Neutrophils
   • Eosinophils
   • Basophils
2. Monocytes ➡️ Macrocytes

Question 8

What do Colony-stimulating factors do?

Answer 8

Stimulate cell division and differentiation of the uni potential or bipotential progenitor cells of the granulocytic and monocytic series.

Question 9

Which cells produce colony-stimulating factors?

Answer 9

Macrophages
Endothelial cells
Fibroblasts

Question 10

What type of compounds belonging to the interleukin family will act as growth factors in hemopoiesis?

Answer 10

Cytokines belonging to the interleukin family

Question 11

What are the functions of interleukins?

Answer 11

Stimulate the proliferation of stem cells

Stimulate differentiation of progenitor and precursor cells of various lines

Question 12

Which type of cells produce most interleukins that act as growth factors?

Answer 12

T lymphocytes

Question 13

Give examples for interleukins acting as hemopoietic growth factors.

Answer 13

IL-3, IL-5, IL-7, IL-11 and IL-18

Question 14

What type of compound is erythropoietin? Where is it produced?

Answer 14

A glycoprotein hormone

In the kidney

Question 15

What is the function of erythropoietin?

Answer 15

Stimulates division and differentiation of the progenitor and precursor cells of the erythrocytic series.

Question 16

Mention a potent stimulant for the increased production of erythropoietin.

Answer 16

Tissue hypoxia (reduction of the oxygen supply to the tissues)

Question 17

Which compounds control the growth and reproduction of the different stem cells?

Answer 17

Proteins called growth inducers.

Question 18

What is the type of growth inducer that promotes growth and reproduction of virtually all the different types of stem cells?

Answer 18

Interleukin-3

Question 19

How many major growth inducers have been described?

Answer 19

4

Question 20

What type type of compounds promote the differentiation of the cells? What do they do?

Answer 20

Differentiation inducers

Each causes one type of committed stem cell to differentiate one r more steps towards a final adult blood cell

Question 21

How is the formation of growth and differentiation inducers controlled? Provide an example.

Answer 21

by factors outside the bone marrow.

RBCs - Exposure of the blood to a low oxygen level for a long time causes growth induction, differentiation and production of greatly increased numbers of RBCs.

WBCs - Infectious diseases cause growth, differentiation and eventual formation of specific WBC types needed to combat infection.