Pathology Cheat Sheet
Make Blood, Handle Blood
Haematopoiesis and blood collection for NEET-PG: fetal to adult sites, erythropoiesis stages, erythropoietin, reticulocytes, and EDTA vs citrate anticoagulants.
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Make Blood, Handle Blood
Haematopoiesis and blood collection for NEET-PG: fetal to adult sites, erythropoiesis stages, erythropoietin, reticulocytes, and EDTA vs citrate anticoagulants.
Normal haematopoiesis and its sites and stages, plus the anticoagulants used in blood specimen collection.
High-yield lines
- Definitive haematopoiesis in the adult occurs in the red bone marrow of the axial skeleton, pelvis, and proximal long bones.
- In fetal life haematopoiesis shifts from the yolk sac to the liver and spleen and finally to the bone marrow.
- All blood cells arise from a pluripotent haematopoietic stem cell capable of self-renewal.
- Erythropoietin from the kidney drives red cell production, and its loss in chronic kidney disease causes normocytic anaemia.
- Erythropoiesis proceeds from proerythroblast to reticulocyte over about 5 to 7 days with progressive nuclear condensation and enucleation.
- The reticulocyte retains residual RNA and appears polychromatic, and its count reflects marrow erythroid output.
- Thrombopoietin regulates platelet production from megakaryocytes.
- Extramedullary haematopoiesis in the liver and spleen is recruited in severe chronic anaemias such as thalassaemia major.
- EDTA in lavender-top tubes chelates calcium and is used for complete blood counts and peripheral smears.
- Sodium citrate in blue-top tubes is the anticoagulant for coagulation studies because its effect is reversible.
- Heparin activates antithrombin and is used for certain chemistry and osmotic fragility tests.
- EDTA cannot be used for coagulation tests because it binds calcium irreversibly, and excess EDTA causes spurious low MCV.
Mapped competency codes
- PA13.1
- PA13.2
Continue into the full chapter
This summary maps to PA13-introduction-to-haematology.
Frequently Asked Questions
Where does haematopoiesis occur in the adult?
In the red bone marrow of the axial skeleton, pelvis, and the proximal ends of the long bones, having migrated there from the fetal liver and spleen.
Why does chronic kidney disease cause anaemia?
Because the kidney produces most of the body's erythropoietin, and its loss removes the survival and proliferation signal for erythroid progenitors, causing a normocytic normochromic anaemia.
Which anticoagulant is used for a complete blood count?
EDTA in a lavender-top tube, which chelates calcium and preserves cell morphology, whereas coagulation tests use reversible sodium citrate.
What does the reticulocyte count indicate?
It reflects the bone marrow's erythroid output, separating anaemias of underproduction from those of red cell loss or destruction.
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