Haematopoeisis

Question 1

There are ____________ blood cells produced everyday

Answer 1

260 billion

Question 2

Why is haematopoeisis a dynamic process?

Answer 2

There is continuous turnover of cells

It has to respond to acute stimuli i.e. infection and bleeding

Question 3

Blood cells make up __% of the blood and plasma makes up __%

Answer 3

45%

55%

Question 4

What are the percentages of RBC, leukocytes and thrombocytes?

Answer 4

44% RBC

1% Leukocytes

Question 5

What are HSC’s?

Answer 5

Haemopoeitic Stem Cells

Question 6

What are LT-HSC’s?

Answer 6

Long Term Haematopoeitic Stem Cells
Can supply an irradiated mouse for a long time
Are able to self renew and maintain the stem cell pool

Question 7

What are ST-HSC’s?

Answer 7

Short Term Haematopoeitic Stem Cells
Can supply an irradiated mouse for only 6 months
They are stimulated to differentiate to become blood cells

Question 8

A ST-HSC can differentiate in to 2 lineages. What are they?

Answer 8

The Myeloid lineage, ST-HSC -> Common Myeloid Progenitor

The Lymphoid lineage, ST-HSC -> Common Lymphoid Progenitor

Question 9

Where does Haematopoeisis occur in the foetus?

Answer 9

0-2 months in the yolk sac
2-7 months in the liver and spleen
5-9 months in the bone marrow

Question 10

Where does Haematopoeisis occur in the adult?

Answer 10

Vertebrae
Ribs
Sternum
Skull
Pelvis 
Proximal ends of the femur

Question 11

Primitive Haematopoesis occurs ____________________________

Answer 11

Outside of the bone marrow during earl foetal development

Question 12

Definitive Haematopoeisis occurs ________________________

Answer 12

Inside the bone marrow from 5 months (In-utero) and through adult life

Question 13

HSC’s are defined as ________ stem cells.

Answer 13

Pluripotent

Question 14

HSC’s undergo divisions to:

Answer 14

• Increase or maintain their numbers (Self-renewal)
• Generate a heterogeneous pool of progenitors
• Sustain haematopoeisis over the lifetime of the individual

Question 15

Stem cells reside in the ________ in a ____ oxygen environment called a niche where they remain ________ until stimulated

Answer 15

Bone Marrow
Low
Inactive

Question 16

What happens when a stem cell is stimulated?

Answer 16

They move towards the vascular niche to differentiate

Question 17

_________ and ___ cells produce several factors that support HSC cells including ________

Answer 17

Osteoblasts and SNO cells

Thrombopoietin

Question 18

Explain the process of RBC differentiation

Answer 18

1. Commited cell (Pro-erythroblast) undergoes ribosome synthesis
2. Haemoglobin is produced
3. Nucleus and organelles are ejected
4. Moves into circulation and becomes a mature erythrocyte

Question 19

How are platelets produced?

Answer 19

1. Commited cell develops (Pro-megakaryocyte)
2. Undergoes endomitosis (Nucleus divides over and over but cell doesn’t divide)
3. Cytoplasmic extensions called proplatelets extend into the blood vessel
4. Flow of blood dislodges proplatelets and they become platelets

Question 20

Outline the EPO/TPO signalling process

Answer 20

1. Erythropoetin or Thrombopoetin bind to either an EPO or TPO receptor respectively
2. Receptor dimerises, bringing molecules on their tails together
3. A set of reactions is set off which causes specific genesto be expressed

Question 21

What transcription factors are needed for RBC formation?

Answer 21

GATA 1
FOG 1
c-myb
p300
Klf1

Question 22

What transcription factors are needed for Megakaryote formation?

Answer 22

GATA 1
FOG 1
GABP α
RUNX1
FLI1

Question 23

What 2 genes are essential for Haematopoeisis?

Answer 23

EPOR

JAK2

Question 24

What are LICs?

Answer 24

Leukaemia Initiating Cells
Small population of cells responsible for tumour maintainence
They are CD34+ and CD38-

Question 25

LICs, particulary those is a ________ state, are thought to be resistant to _____________________ therapies and contribute to disease relapse

Answer 25

Quiescent

Chemotherapy and Targeted therapies