Erythropoiesis Flashcards
STILL NEEDS COMPLETING especially with clinically relevant lecture content.
Erythropoiesis
formation of erythrocytes from stem cells
Haematopoiesis
formation of the blood’s cellular components. This is a continuous process of replenishment.
Erythropoietin
a.k.a. EPO.
An enzyme with various roles; activates the development of erythroid cell precursors to proerythroblasts
Sites of EPO production/release in the foetus
- Yolk sac
- Liver
- Kidney
- Spleen
- Bone marrow
Sites of EPO production/release in the adult
- Renal interstitium (kidney)
What is the stimulus for EPO secretion?
The tissue needs for oxygen.
This is identified as renal hypoxia.
What factors might lead to renal hypoxia and thus erythropoietin secretion?
- Normal oxygen levels but low delivery e.g. circulatory failure/anaemia
- Low oxygen levels = hypoxia
Outline the steps that follow renal hypoxia
- Increased renal secretion of erythropoietin
- EPO transported by the blood to the bone marrow
- EPO binds to receptors on CFU-E (erythroid cell precursors)
- EPO also accelerates the release of reticulocytes into the blood
- This aims to increase the number of circulating erythrocytes and thus restore oxygen transport
True/false: the lifespan of compatible transfused erythrocytes is shorter than that of erythrocytes produced within that animal’s body.
True.
e.g. in dog, transfused erythrocyte lifespan = 21 days compared to normal 120 days.
This is due to the process of blood taking and transport into another animal.
What happens to erythrocytes as they age?
- They become more fragile
- They may become swollen due to failure of the normal membrane function
- They lose sialic acid residues from their surface, exposing galactose moieties that induce their phagocytosis.
What is the average lifespan of erythrocytes in dogs?
120 days
What is the average lifespan of erythrocytes in horses?
145 days
What is the average lifespan of erythrocytes in cattle?
160 days
What is the average lifespan of erythrocytes in cats?
70 days
When erythrocytes reach the end of their lifespan, the iron in them is released from haemoglobin. What happens next?
2 options:
- Iron is conveyed to bone marrow by transferrin
- Iron is stored as insoluble iron in macrophages and hepatocytes as ferritin