Intro to Haemopoiesis

Question 1

What is haemopoiesis?

Answer 1

• Haemopoiesis is the formation of red cells, white cells and platelets
• All of these cells are derived from haemopoietic stem cells

Question 2

Describe the structure of the bone marrow (bone anatomy)

Answer 2

• The spongy bone in which haematopoiesis occurs is a reticulin connective tissue network like spiderweb with Mesenchymal Stromal cells, macrophages and other supportive cells to assist haemopoietic cells
• Bone marrow is about 50% empty space and 50% cells

Question 3

Describe the function of the bone marrow (cellular)

Answer 3

• Normal bone marrow function
– production of 
• red cells
• white cells
 • Platelets

– Requires
• nutrients including iron, B12, B6, folate, amino acids, energy
• supportive cells- stromal cells, cytokines

Normal bone marrow function
– CYTOKINES-
• Erythroid- includes ERYTHROPOIETIN 
• Granulocytes- includes G-CSF, GM-CSF 
• Lymphocytes- Interleukins
• Platelets- THROMBOPOIETIN
• OTHER
– Stromal Cells, Nucleic acids, amino acids etc.

Question 4

What are cytokine cells and what do they do in haematopoiesis?

Answer 4

Cytokines are small proteins that are involved cell signalling

They are released by macrophages, lymphocytes, endothelial cells, fibroblasts and stromal cells, to affect the behaviour of other cells

In haematopoiesis, the presence of different cytokines dictate which cells are produced i.e. erythropoietin will induce the production of erythrocytes

Question 5

Describe the differentiation of haemopoietic cells

Answer 5

HSC –> Common Myeloid Progenitor + Common Lymphoid Progenitor

Myeloid –> Megakaryocyte + Erythrocyte + Myeloblast

Megakaryocyte –> Thrombocytes

Erythrocytes –> RBC

Myeloblast –> Basophil, Eosinophil, Neutrophil, Monocyte

Lymphoid –> small lymphocyte –> T cells + B cells

Question 6

Describe haemopoiesis

Answer 6

The formation of blood cellular components, derived from haematopoietic stem cells in an appropriate nutritional environment (iron/B12 etc), with supporting cells

Question 7

Characteristics of haemopoietic stem cells

Answer 7

Pleuripotent

Displays CD34 on the surface

Question 8

What are some causes of decreased numbers of RBCs, WBCs and platelets?

Answer 8

Red cells
Marrow failure syndromes, Iron/B12/Folate Deficiencies, Blood loss etc. Renal Failure with reduced production of EPO

– White cells
Viral Infections, Post Chemotherapy, Reduced G- CSF stimulation (rare, inherited)

– Platelets
Immune Destruction(ITP), Drugs etc.

Question 9

What are some causes of increased numbers of RBCs, WBCs and platelets?

Answer 9

Red cells
Hypoxia, Renal Tumours- secretion of EPO

• Whitecells
Myeloproliferative disorder, Secondary: Infection, Inflammation

• Platelets
Essential thrombocythaemia, Inflammation, Infection