Erythropoiesis Flashcards
General stages of erythropoiesis
Myeloid stem cell ->proerythroblast-> erythroblast -> reticulocytes ->mature RBC
Duration of erythropoiesis
14-21 days
Where does erythropoiesis take place?
Bone marrow
What is erythropoietin?
Growth factor that stimulates MSC proliferation and differentiation
DNA synthesis requires..?
Folate and vit B12
Maturation of erythroblast
- Filled with Hb which requires Fe
- nucleus in erythroblast is reabsorbed/extruded so that more Hb can be added
- remnants of organelles
What is diapedesis?
migration of reticulocytes through capillaries for further maturation into mature RBC
Indicator of bone marrow activity/erythropoiesis and how it is interpreted
amt of reticulocyte in circulation (normal is ~1%)
- too little -> erythropoiesis not functioning well
- too much -> abnormally high activity
How long for reticulocytes to mature after entering circulation?
1-2 days
Regulation of erythropoiesis and how the feedback loop works
Changes in arterial partial pressure of oxygen (PaO2); negative feedback loop
- decrease -> HIF-1a synthesised and released into circulation -> stimulate production of erythropoietin (EPO) by kidney -> increased erythropoiesis -> increased mature RBC and O2 carrying capacity
- increased O2 carrying capacity reliefs initial stimulus on EPO production
What are some factors that can affect arterial partial pressure of O2?
- anaemia
- cardiopulmonary issues
- atmospheric PO2
- O2 consumption (affected by strenuous activities -> increased consumption, less O2 avail in blood)
Homeostasis of blood system and some diseases as a result of imbalance
Balance btw production (erythropoiesis) and clearance (RBC loss/destruction)
- destruction > production -> anaemia
- production > destruction -> polycythaemia (rare; happens when neoplasia/ blood doping)
Factors affecting RBC loss
- usual clearance (remove aged RBC)
- blood loss
- immune destruction
- genetic defects affecting fn of Hb
Factors affecting erythropoiesis
- hypoxia (lack of O2 -> increase erythropoiesis)
- nutrients availability
- neoplasia
- erythropoietin/ blood doping
Ways to assess derangements of erythropoietic system
- full blood count
- reticulocyte count
- peripheral blood film
not as impt: BM aspirates (evaluate integrity of bone marrow), bilirubin, ferritin level
What to look out for in FBC?
- Hb -> most impt parameter when assessing if one has anaemia or not
- RBC
- MCV
- MCH
- MCHC
- Haematocrit (give overall view of total volume of RBC)
What is MCV?
mean corpuscular vol (vol per RBC)
Interpretation of MCV
- normocytic = normal
- microcytic = smaller than normal
- macrocytic = larger than normal (implication is that RBC cannot pass through capillaries to get into circulation and burst)
What is MCH?
mean corpuscular Hb (amt of Hb per RBC)
What is MCHC?
mean concentration (MCH/MCV = conc of Hb per RBC)
Interpretation of MCHC
- normochromic -> normal
- hypochromic -> [Hb] less than normal -> lighter in colour
- hyperchromic -> [Hb] more than normal -> darker in colour
How is anaemia assessed?
RBC quantity and quality (size and shape)
Definition of anaemia
Reduced Hb and/or reduced RBC
(Classification of anaemia) cause of anaemia if RBC is normocytic
Increased RBC loss - eg: acute blood loss
Reduced RBC production - eg: renal disease
