This document summarizes the normal constituents of blood, including their structure and functions. It discusses hematology and hematopoiesis, the process of blood cell production in the bone marrow and lymphoid tissues. The major cell types produced - red blood cells, white blood cells (neutrophils, lymphocytes, etc.), and platelets - are each described in terms of their development, structure, and role in the body. Regulation of hematopoiesis and the different cell lineages (myeloid vs. lymphoid) is also overviewed.

1. Normal Constituents of Blood,
Their Structure and Functions
Dr. Salman Ansari(MBBS)
Tutor, Dept. of Pathology
Kanachur Institute of Medical Sciences

2. Index
● Hematology, hematopoiesis
● Myeloid tissue, lymphoid tissue, regulation of
hematopoiesis
● RBCs
● WBCs
● Platelets

3. Hematology
“Study of the normal and pathologic aspects of blood
and blood cells”

4. Hematopoiesis/hemopoiesis
“Process of production of blood cells”
Hematopoietic system:
- Consists of all the organs and tissues involved in
hematopoiesis - Myeloid tissue and Lymphoid tissue
Hematopoietic stem cell(HSC): Progenitor of all the cells in blood -
gives rise to both myeloid and lymphoid series

6. Myeloid tissue
Consists of:
- Bone marrow
- Cells derived from it, like:
RBC(erythrocytes)
WBCs(leukocytes): which consist of
granulocytes(neutrophils, eosinophils and basophils),
monocytes and agranulocytes(lymphocytes)
Platelets(thrombocytes)

7. Lymphoid tissue
- Thymus
- Lymph nodes
- Spleen

8. Sites of hematopoiesis
● In fetus: yolk sac, liver, spleen, bone marrow
● In infants: bone marrow
● In Adults: bone marrow

11. Regulation of hematopoiesis
Hematopoiesis is regulated by a number of hematopoietic growth
factors or cytokines, such as
● Stem cells: Stem Cell Factor, Interleukin-6(IL-6) and FLT3-
ligand
● Common Myeloid Progenitor(CMP) cell: Granulocyte-
Macrophage Colony Stimulating Factor(GM-CSF), Granulocyte
CSF(G-CSF), erythropoietin, thrombopoietin
● IL-3, 5, 6 and 11

12. Regulation of lymphopoiesis
Interleukins like: IL-1, 2, 4, 5, 6, 7 and 9

14. Myeloid series Lymphoid series
RBCs(erythrocytes) B-cells
WBCs(neutrophils,
eosinophils, basophils,
monocytes)
T-cells
Platelets(thrombocytes) NK cells

15. RBC/erythrocytes
Production of RBCs is called Erythropoiesis.
Stages of erythropoiesis:
Proerythroblast → Early Erythroblast → Intermediate
Erythroblast(normoblast) → Late erythroblast → Reticulocyte
→ Mature RBC

17. Structure
- Biconcave disc 7.2 µm in diameter
- Non-nucleated
- Central pallor

19. Function
1. Oxygen transport to tissues
2. CO2 transport

20. WBCs/leukocytes
Process of formation of WBCs - “leukopoiesis”
- Myeloid series - Myeloid stem cell develops into
granulocytes(neutrophils, eosinophils, basophils) -
“myelopoiesis”
- Lymphoid series - Lymphoid stem cell develops into
agranulocytes(lymphocytes) - “lymphopoiesis”

24. Neutrophil/polymorph
- 40-80% of WBCs
Structure:
- Diameter: 13 µm
- Multi-lobed nucleus
- Fine pink granules
Functions:
- 1st line of defense
- Acute inflammation

25. Eosinophil
1-6% of WBCs
Structure:
- Diameter: 12-17 µm
- Bilobed nucleus
- Coarse orange granules
Functions:
- Allergic reactions
- Parasitic infections

26. Basophils
0-1% of WBCs
Structure:
- Bilobed nucleus
- Coarse blue granules
Function:
- Allergic reactions(they contain histamine granules)

27. Monocytes
2 to 10%
Structure:
- Size: 15 to 18µm
- Nucleus: large, kidney-shaped
- Cytoplasm: Blue
Function:
Phagocytosis - transform into macrophages

28. Lymphocytes
20-40%
2 types: Small lymphocyte (6 to 10µm)
Large lymphocyte (12-15µm)
Structure:
- Nucleus: single, no lobes
- Cytoplasm: Pale blue
Function:
produce antibodies and cell-mediated immunity

29. Platelets/thrombocytes
Process of development is called thrombopoiesis

30. Structure:
Size: 1 to 3µm
Lilac color
Purple red granules
Function:
Stop bleeding - hemostasis and thrombosis

36. For notes,
scan:
References:
● Harsh Mohan - Practical Pathology - 5th edition
● Ramadas Nayak - Textbook of Pathology for Allied
Health Sciences
Questions:
salman.s.ansari92@gmail.com
For PPT, scan: