haematopoiesis

Question 1

define haematopoiesis

Answer 1

process by which mature blood cells are derived from stem cells in the bone marrow

Question 2

what are the 8 main lineages

Answer 2

1. erythrocytes
2. platelets
3. eosinophils
4. basophils
5. neutrophils
6. monocytes/macrophages
7. T lymphocytes
8. B lymphocytes

Question 3

how can you measure the number of stem cells

Answer 3

haematopoietic stem cells express antigen CD34

Question 4

how is haematopoiesis regulated?

Answer 4

• erythropoietin transcription factors
• EPO regulates erythrocytes
• thrombopoietin (TPO) controls platelets production
• IL3 controls the differentiation to erythroid, megakaryocyte, MGM

Question 5

bone marrow examination

Answer 5

• marrow aspirated for cytology of haematopoietic cells
• trephine biopsy used for histology of marrow (architecture, cellularity)
• stem cell count assessed indirectly by colony assays or measurement of CD34 positive cells
  (immuno-phenotyping, cell surface markers)

Question 6

haematopoietic tissue origin

Answer 6

• transient primitive blood cells from mesoderm in blood islands of yolk sac
• definitive cells from endothelium in the aorta-gonad-mesonephros (AGM) region
• site of haematopoiesis then shifts to fetal liver, then bone marrow