haemopoiesis Flashcards
Where does haemopoeisis begin ?
embryonic yolk sac (primitive haemopoisis)
Aortic Gonado Mesonephros (definitive haemopoesis)
why is the Vitelline artery the specific site for formation of blood cells
it has the highest sensitivity for hypoxia & can sense the need for new RBCs
when does haemopoiesis begin ?
3rd & 4th week of embryonic life
Haemopoeitic sites and their timelines
1) Yolk sac (3rd week - 6th week)
2) liver & spleen (6/8thweek to 6/7th month of fetal life)
3) bone marrow (6/7th month to 14 months EUL)
What is Extramedullary haemopoiesis?
Abnormal production of blood by the liver in adult life, usually occurs in disease states
What is a stem cell ?
any cell that has the ability to differentiate and self renew. moves to sites based on demand
What is the cluster of differentiation in a normal stem cell?
CD34+, CD38- , CD33- , THY1+, C-kit+
What are hemangioblasts ?
multipotent cells that give rise to haemopoetic & endothelial cells
What is homing ?
this is the movement of stem cells from the peripheral blood to the bone marrow.
it is regulated by transcription factors.
Growth Factor responsible for homing ?
Stromal-Derived Factor 1 (SDF-1)
*binds to CXCR4 receptors on the surface of stem cells
what is mobilization?
movement of stem cells from the bone marrow to the peripheral blood
growth factors responsible for mobilization ?
1) granulocyte monocyte colony stimulations factor (GMCSF)
2) granulocyte colony stimulating factor (GCSF)
What is HIME?
Haemopoietic Inductive Microenvironment - an envt that is conducive & allows adaptability, survival & proliferation of stem cells
What do cells are contained in the stroma ?
1) adipocytes
2) fibroblasts
3) mesenchymal stem cells
4) endothelial cells
5) macrophages
6) collagen
7)osteoblasts
what are the growth factors secreted by the stroma ?
Interleukin 5, 13, 3
eotaxin
what are growth factors ?
these are glycoprotein hormones that regulate the proliferation and differentiation of haemopoietic progenitor cells
*may act locally (SCF) or circulate in plasma (GCSF)
characteristics of growth factors
1) glycoproteins
2) synergic in action
3) act on specific receptors
4) work in hierarchy
5) anti-apoptotic
6) pro-proliferative
7) some are positive in action while some are negative in action
how many percent of erythropoietin is synthesized in the kidney ?
90%
*thrombopoietin is made largely in the liver
how many percent of erythropoietin is synthesized in the kidney ?
90%
*thrombopoietin is made largely in the liver
_ are a major source of growth factors
Stromal cells
Growth factors with positive action include (promote proliferation)
1) IL-3
2) transforming growth factor alpha
growth factors with negative action
1) transforming growth factor beta
2) interferon gamma
*used as a treatment for hepatitis
*contraindicated in pregnant women(can lead to bone marrow suppression)
where is interleukin 3’s activity?
on the lymphoid/myeloid & megakaryocyte/erythrocyte progenitors
__ & __ enhance neutrophil, macrophage/monocyte production?
granulocyte monocyte colony stimulating factor (GMCSF) & granulocyte colony stimulating factor (GCSF)
