Hematopoiesis Flashcards
When does hematopoiesis begin?
Early in embryonic development
What are the three phases of hematopoiesis?
Yolk sac phase
Hepatic phase
Bone marrow phase
What is extramedullary hematopoiesis?
Occurs outside the bone marrow
Yolk sac phase
Hepatic phase
What characterizes yolk sac phase?
Begins 3rd week
Blood islands in yolk sac wall
Erythropoiesis and some thrombopoiesis
What characterizes hepatic phase?
2nd trimester of pregnancy
Mainly erythropoiesis some thrombopoiesis and leukopoiesis
What characterizes the bone marrow phase?
Begins towards end of 2nd trimester through adulthood
Where does bone marrow phase take place?
Birth-puberty: Throughout skeleton
Puberty-adulthood: Axial skeleton only
What two things can a hematopoietic stem cell become?
Lymphoid progenitor: cell types of lymphoid lineage
Myeloid progenitor: cell types of myeloid lineage (erythrocytes and platelets and granulocytes)
What are two essential properties of HSCs required for hematopoiesis?
Pluripotency
Self-renewal
Where are HSCs found at 3 months and 4 months of gestation?
3 months: liver and fetal placenta
4 months: bone marrow
What does HSC mobility mean?
Can move from bone marrow to peripheral blood under condition of stress
What can stimulate HSC mobility into peripheral blood?
Granulocyte colony stimulating factor (G-CSF)
What occurs when precursors become committed?
They lose the capacity for self-renewal and proliferate rapidly in response to growth factors
What is true about growth factors in the process of hematopoiesis?
Lineage-independent growth factor receptors are important early whereas lineage-specific growth factor receptors become important later
What are the cells intermediates leading up to thrombopoiesis and erythropoiesis?
Hemopoietic stem cell
Common myeloid progenitor
Megakaryocyte erythrocyte progenitor
Megakaryocyte progenitor (platelet) or Erythrocyte progenitor (RBC)
