Erythropoiesis: Flashcards
What do the products of erythropoiesis provide ?
- A vehicle for the transport of haemoglobin, combines with O2 in lungs.
- Transport CO2 from tissues to lungs for excretion.
What is the RBC lifespan?
120 days
What is the lineage of the eryrocyte?
Myeloid
What are the progenitor cells for an erythrocyte?
BFU-E
CFU-E
What are the precursor cells for an erythrocyte?
Pronormoblast Basophilic normoblast Polychromatic normoblast Orthochromic normoblast Polychromatic erythrocyte (reticulocyte)
What does the proliferation of blood cells occur simultaneously to?
The differentiation and maturation of the erythrocyte.
Where do red cells mature?
In the marrow, as they mature their cytoplasm changes. (from basophilic to eosinophilic)
Where are red cells recycled?
In the spleen.
Why do the red cells become eosinophilic and turn salmon pink with the addition of the Leishman stain ?
As the cell becomes hemoglobinized and stains with eosin, the acidic part of the Leishman stain.
What is a reticulocyte and where it is newly released from?
This is a young erythrocyte, newly released from the bone marrow into the peripheral blood.
Do reticulocytes have RNA ?
Yes they do, it is residual RNA from the erythrocyte precursors.
What stain is used on reticulocytes for their RNA?
A supravital stain such as new methylene blue or brilliant cresyl blue.
What is anoxia/hypoxia?
This is where there is less than a normal concentration of O2 in the blood.
Triggers EPO
What does the kidney do in response to hypoxia?
It triggers the production of erythropoietin.
EPO stimulates erythropoiesis by increasing the number of progenitor cells committed to erythropoiesis.
Where does EPO join on the precursor erythrocyte cells?
On the receptors of CFU/BFU cells.
What is given to patients suffering from renal failure?
Given commercially recombinant erythropoietin.
What does EPO stimulate?
The production of RBC; leading to an increase in the number of RBC and the level of H available to carry O in the tissues.
What is the pathway that erythropoietin receptor binds to?
JAK-STAT pathway - signals and effects transcription and the level of DNA and mRNA synthesis - increased levels of proliferation.
Does erythropoietin affect the rate of the transfer of iron?
It does, it affects the rate of transfer of iron to the normoblast and the rate of haem synthesis.
What is another name for normal erythropoiesis?
Normoblastic
What is a myelogram?
This is the examination of the marrow.
What is the proportion of late normoblast in the marrow?
70%
What is the proportion of inter normoblast in the marrow?
20-30%
What is the proportion of early normoblast in the marrow?
1-4%
What is the proportion of pro-normoblast in the marrow?
1%
What is MER?
This is the myeloid/erythroid ratio; this is the ratio of immature white cells to immature red cells in the marrow.
What is the normal MER?
White:Red (marrow)
4:1
Due to lifespan of white cells in blood - short vs RBC 120 days.
What is an example of MER in a patient with Leukaemia?
20:1
When would there be a reduction in the MER ratio?
- severe blood loss
- destruction of RBC
= increase in red cell precursors to boost red cell production
What is produced instead of a normoblast in the marrow in the case of a vitamin B12 or FOLATE deficiency?
The marrow produces a megaloblast - large abnormal red cell precursors.
‘Megaloblastic’
What is hyperplastic marrow?
This is an overproduction of cells in the marrow.
What is aplasia or aplastic bone marrow?
This means that there is NO production of cells in the marrow.
During severe blood loss or blood destruction what happens to the speed of cell division?
The intermitotic time: this shortens as there is an increase in the production of red cells as EPO is triggered from the lack of red cells.
What occurs during cell division in iron deficiency anaemia?
Extra cell division resulting in smaller microcytic cells.
What anaemia occurs when one or more mitotic steps are omitted?
Megaloblastic anaemia (due to B12 or folate deficiency) Macrocytic cells are produced.
What are some of the tests used in the measurement of erythropoietin activity?
FBC Blood film Marrow microscopy EPO assay Ferrokinetics - Fe59 (transferrin) Reticulocyte count Blood Vol Red cell lifespan studies - Cr51
What is the function of Ferrokinetics?
This is a test for the measurement of erythropoietic activity - isotope Fe5 is injected, transferrin takes it up it is transported into the marrow.
If the isotope reappears later in the H molecule in the red cells = normal E
What is the function of red cell lifespan studies?
This is where the isotope Cr51 is tagged on a blood sample taken from the patient.
Inject cells back into patient.
Measure the lifespan of the injected cells
120 days.
What is the name of the nuclear remnants found in a patient’s red blood cells post splenectomy?
Howell Jolly Body
Spleen incapable of removing some nuclear material, therefore it remains in the cell.
What are the two types of bone marrow examinations that are often done together?
Marrow Aspiration
Marrow Trephine
What does the marrow aspiration draw out?
A sample of the liquid portion of the marrow.
What does the marrow trephine draw out?
Removes a small, more solid part of the bone marrow.
Which bone is a bone marrow examination taken from?
Hip bone - os coxae
