FORMATION OF WHITE BLOOD FORMATION OF WHITE BLOOD CELLSCELLS

Dr. B.L. Mtinangi.Dr. B.L. Mtinangi.

Department of PhysiologyDepartment of PhysiologySchool of Medicine, MUHAS

November, 2015

FORMATION OF WBCFORMATION OF WBC

As for the Rbc, the formation of Wbc originates from the COMMON PROGENITOR CELL ie uncognisable cell which develop to the UNCOMMITTED STERM CELL and this changes to COMMITTED STERM CELL

FORMATION OF WBC CONT.FORMATION OF WBC CONT.Committed sterm cell can either develop

into:• Myeloblast series or• Monoblast or• Lymphoblast series.Myeloblast changes into Promyelocyte & the

Promyelocyte to Myelocyte which will either develop into

• NEUTROPHIL or BASOPHIL or EOSINOPHIL.

FORMATION OF WBC CONT.FORMATION OF WBC CONT.

Monoblast develop into:• Monocyte in the circulating blood• Tissue Macrophage ie the Monocyte that

has moved into various tissues.Lymphoblast from Lymphogenous organs

develop into Prolymphocyte which will then develop into:

• Large Lymphocyte &• Small Lymphocyte

WBC CONT.WBC CONT.

White blood cells are Leucocytes & Macrophages that are involved in the defence mechanisms against:

• Bacteria• Viruses• Fungus &• Parasites

WBC CONT.WBC CONT.Mechanism of action of Wbc is either• Phagocytic eg neutrophil, eosinophil,

basophil & monocytes OR• Antibodies formation eg lymphocytesWbc are of two types:• With granules (Granulocytes)• Without granules (Agranulocytes)Normal Wbc count ranges from 4000 to

11000/micro litre

WBC CONT.WBC CONT.

Wbc with granules (granulocytes) are • Neutrophils 40 – 70% (60%)• Eosinophil 1 – 4% (3%)• Basophil 0 - 2% (1%)Wbc without granules (agranulocytes)• Lymphocytes 20 – 45% (30%)• Monocytes 4 - 8% (6%)NB. Platelets are sometimes grouped as

Wbc

FUNCTIONS OF WBCFUNCTIONS OF WBC

Granulocytes and Monocytes are for• PHAGOCYTOSISLymphocytes are for IMMUNITY ie • Cell mediated immunity &• Antibody formationPlatelets are for blood clotting

(COAGULATION) mechanisms

Type Of White Blood Cells

% By Volume Of WBC Description Function

Neutrophils 60 – 70 % Nucleus has many interconnected lobes; blue granules

Phagocytize and destory bacteria; most numerous WBC

Eosinophils 2 – 4 % Nucleus has bilobed nuclei; red or yellow granules containing digestive enzymes

Play a role in ending allergic reactions

Basophils < 1 % Bilobed nuclei hidden by large purple granules full of chemical mediators of inflammation

Function in inflammation medication; similar in function to mast cells

Lymphocytes (B Cells and T Cells)

20 – 25 % Dense, purple staining, round nucleus; little cytoplasm

the most important cells of the immune system; effective in fighting infectious organisms; act against a specific foreign molecule (antigen)

Monocytes 4 – 8 % Largest leukocyte; kidney shaped nucleus

Transform into macrophages; phagocytic cells

WBC CHARACTERISTICSWBC CHARACTERISTICS

Each Wbc has specific distinguishing characteristics in terms of:

• Cell size• The shape of Nuclear• Cytoplasmic content• Type of granules &• Phagocytic activity of the cell

LIFE SPAN OF WBCLIFE SPAN OF WBCThe life span of the Wbc differs depending

on the type of Wbc:• Granulocytes have a life span of 4 to 8 hrs

in the circulation and 4 to 5 days in tissues• Monocytes have a short transit in

circulation then go to TISSUES as Tissue macrophages

• Lymphocytes have a life span of about 100 to 300 days, tend to recirculate. Some are known to have a life span of 7 years

MECHANISM OF CELL MECHANISM OF CELL PHAGOCYTOSISPHAGOCYTOSIS

• Margination ie lining of cells(Wbc) on the capillaries due to bacteria products or toxins

• Diapedesis ie squeezing through small pores in blood capillaries

• Migration ie ameboid or psedopodia motion esp Neutrophils & macrophages

• Chemotaxis ie movements due to bacteria toxins & inflammation.

All cause a directional migration of NEUTROPHIL & MACROPHAGES to the site of injury or infection

PHAGOCYTOSIS CONT.PHAGOCYTOSIS CONT.The process of phagocytosis:• Bacteria are ENGULFED by

Pseudopodia & Fusion• Bacteria then lies within a cel l

vacuole with phagosome• Lysosomal or digestive enzymes are

secreted into phagosome causing• Degranulation & Lysis of the bacteria

leading to DEATH

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