Introduction to Hematology – Study Notes
1. What is Hematology?
- Definition: The branch of medicine that deals with the study of blood, its components, and the organs that produce them.
- Scope:
- Normal blood physiology
- Blood‑related diseases (anemia, leukemias, clotting disorders, etc.)
- Laboratory diagnostics (CBC, coagulation tests, bone‑marrow examination)
- Therapeutic interventions (transfusions, anticoagulation, stem‑cell transplantation)
2. Major Components of Blood
| Component |
Approx. % of Whole Blood |
Primary Functions |
Key Laboratory Parameters |
| Plasma |
55 % |
Transport of nutrients, hormones, waste; clotting factor reservoir |
Total protein, albumin, globulins, electrolytes, coagulation profile |
| Red Blood Cells (RBCs) |
40‑45 % |
Oxygen delivery (via hemoglobin), CO₂ transport |
Hemoglobin (Hb), Hematocrit (Hct), RBC count, Mean Corpuscular Volume (MCV) |
| White Blood Cells (WBCs) |
<1 % |
Immune defense, inflammation, tissue repair |
Total WBC count, differential (neutrophils, lymphocytes, monocytes, eosinophils, basophils) |
| Platelets |
<1 % |
Primary hemostasis (clot formation) |
Platelet count, mean platelet volume (MPV) |
3. Hematopoiesis – Blood Cell Production
| Site (developmental stage) |
Cell Lineage |
Key Growth Factors |
| Yolk sac (embryonic) |
Primitive erythrocytes |
— |
| Fetal liver & spleen |
Definitive erythrocytes, megakaryocytes, some leukocytes |
Erythropoietin (EPO), thrombopoietin (TPO) |
| Bone marrow (post‑natal) |
All lineages (RBCs, WBCs, platelets) |
EPO, G‑CSF, GM‑CSF, M‑CSF, IL‑3, TPO, stem‑cell factor (SCF) |
- Stem cell hierarchy:
- Hematopoietic stem cell (HSC) – multipotent, self‑renewing.
- Multipotent progenitor (MPP) – limited self‑renewal, commits to myeloid or lymphoid lineages.
- Committed progenitors (e.g., CFU‑E for erythrocytes, CFU‑G for granulocytes).
- Mature cells – functional RBCs, leukocytes, platelets.
4. Basic Laboratory Tests in Hematology
| Test |
What It Measures |
Clinical Relevance |
| Complete Blood Count (CBC) |
RBC, WBC, platelet numbers; Hb, Hct, indices (MCV, MCH, MCHC) |
Screening for anemia, infection, thrombocytopenia, leukemia |
| Peripheral Blood Smear |
Morphology of cells |
Detects sickle cells, blasts, parasites, platelet clumping |
| Reticulocyte Count |
Young RBCs (immature) |
Evaluates marrow response to anemia |
| Coagulation Panel (PT, aPTT, INR, fibrinogen) |
Clotting factor activity |
Monitors antico |