1. Histology of Blood

2. BLOOD
Blood consists of fluid element (plasma) and formed elements cells: erythrocytes, platelets and leukocytes.
Adult has about 5.5 Liters
Blood is usually studied in stained smears using Leishmann or Giemsa stains.
Blood cells are produced in bone marrow from stem cells.

3. Composition of Blood

4. Erythrocytes (RBCS)
Shape: Biconcave disks which has no nucleus (large surface area for gas exchange).
Dimention: They are µm in diameter and 2 µm in thickness in stained smears.
Rouleaux appearance in slow circulation.

5. Flexible; squeeze when pass through capillaries.
Survive about 120 days in circulation.
Old RBC removed by macrophages in spleen and bone marrow.
Contains hemoglobin which is an endogenous pigment (greenish yellow) to carry oxygen.

6. Adaptations of RBCS to function
Biconcavity: increase surface area/decrease distance for gas exchange.
Plasticity: passage through narrow capillaries
Rounded edges: no injury.
No organelles: space for hemoglobin.
Carbonic anhydrase: carry CO2.

7. Numbers of RBCs Normal: 4-6 million per mm³. Polycythemia (+)
Severe dehydration.
Hypoxia (+BM) physilogical (high altitude) or pathological (heart and lung diseases).
Anemia
(-)
Deficiency (iron, pr., vit., hormones….)
Aplastic (b.marrow affection as in leukaemia/drugs/X-ray/..
Haemolytic anemia.
Haemorrhagic anemia

8. Leucocytes Number: 6-10,000 per mm³
Granulocytes (polymorphonuclear leukocytes) have specific granule
neutrophils 60-70%
acidophils 2-4%
basophils 0.5-1%
Agranulocytes lack specific granule
lymphocytes 20-30%
monocytes 3-8%
Platelets 200, ,000 per mm³

9. Granular Leukocytes
Eosinophil
2-4%
Neutrophil
60-70%
Basophil
0.5-1%

10. Agranular Leukocytes
Lymphocyte
20-25%
Monocyte
3-8%

11. Neutrophils 12-15 µm in diameter. Multi-lobed nucleus.
Human females may have inactivated second X chromosome (drumstick).
Specific granules: Alkaline PO4ase, collagenase, lactoferrin, lysozyme and phagocytins.
Azurophilic granules: deep red or purple, primary lysosomes containing acid hydrolase myeloperoxidase, lysozyme.

13. Neutrophils Lifespan: 1-4 days in tissue.
Active phagocytes which are important in defense against infection.
Form H2O2 and powerful cytotoxins.
Lysozyme breaks down bacterial cell wall.

15. Eosinophils About 12-15 µm in diameter Bi-lobed nucleus
Many granules (primary lysosomes)
Kill parasites, especially worms
Phagocytose Ag-Ab complexes to terminate allergic reactions.

17. Basophils Scarce, hard to find in smears S-shaped nucleus
Ig E receptors on their plasmalemma
Many blue (basophilic) specific granules with heparin and histamine
Content of specific granules cause vasodilatation
Nonspecific granules are lysosomes
Function as initiator of the inflammatory process
May act as supplement of mast cell function

19. Lymphocytes 20-25 % of circulating leukocytes
6-8 µm dia most common; large ones up to 18 µm dia also found in blood
Dark, heterochromatic nucleus
Thin layer of blue cytoplasm, many ribosomes
Three types: T-cells(80%), B-cells (15%) and Null cells(remainder)
Differentiation occurs in bone marrow (B cells) and thymus (T cells)
T-cells may live many years, B-cells live a few months

20. Lymphocytes
B cells form plasma cells, function in humoral immunity via immunoglobulins
T cells function in cell-mediated immunity
Some T cells with “memory” of antigen exposure survive long periods; immunization
Null Cells are composed of: Stem cells and Natural killer cells
NK cells kill some foreign and virally alerted cells

22. Monocytes 12-20 µm in diameter
Oval, eccentric, horseshoe or kidney shaped nucleus
Lighter stained nucleus than large lymphocytes
Cytoplasm light blue due to azurophilic granules (lysosomes) and ribosomes
In tissues, differentiate into macrophages
Lifespan hours
Do not re-enter into circulation

24. Platelets Non-nucleated disk-shaped cell fragments
2-5 µm in diameter, derived from megakaryocyte cytoplasm
Life span less than 14 days in blood
Hyalomere is the peripheral clear region
Granulomere is the central darker region

26. Platelet Function Blood clotting; aggregation of platelets
Clot retraction due to actin/myosin
Clot removal due to plasmin which is a proteolytic enzyme

27. THANK YOU