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
Which species are these erythrocytes from?
These are equine erythrocytes.
There is characteristic rouleaux formation (clustering of RBCs in standing blood) - this is a normal finding in horses.
Which species are these erythrocytes from?
These are bovine erythrocytes.
There is characteristic crenation and variation in size.
Which species are these erythrocytes from?
These are camelid erythrocytes.
They have a characteristic ellipsoid shape.
Which species are these erythrocytes from?
These are canine erythrocytes.
They are of uniform size and show central pallor, indicating their concave shape.
Which species are these erythrocytes from?
These are feline erythrocytes.
They are smaller than other species and show anisocytosis (variation in size).
They show scarce central pallor (less concave than other species).
Which species are these erythrocytes from?
These are avian erythrocytes.
They are larger and nucleated.
The earlier stages are more rounded and may be binucleate.
Occasionally cells lose their nucleus and are termed erythroplastids.
Which species are these erythrocytes from?
These are reptile erythrocytes.
They are larger and nucleated.
The earlier stages are more rounded and may be binucleate.
Occasionally cells lose their nucleus and are termed erythroplastids.
Erythrocytes are metabolically active (they need to maintain an electrolyte gradient); how do they obtain energy for this?
Via anaerobic metabolism of glucose.
This avoids the need for mitochondria and also avoids consumption of any of the oxygen they are carrying.
