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A Handbook of Biology

B. FØRMËD ËLËMËÑTS (RBÇ, WBÇ & PLÅTËLËTS)

RËD BLØØD ÇËLLS ( RBÇ ) ØR ËRÝTHRØÇÝTËS :

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Erythrocytes are the most abundant of all the cells in

the blood.

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Biconcave non-nucleated cells. No mitochondria,

Golgi complex etc. Red colour is due to haemoglobin

(iron containing protein). Normal Hb level is

12-16 gms/100 ml.

Count: 5-5.5 millions/ mm³

Formed in: Red bone marrow

Average lifespan: 120 days worn-out RBCs are destroyed

in spleen (graveyard of RBCs).

Function: CO2 and O2 transport.

WHÏTË BLØØD ÇËLLS ( WBÇ ) ØR LËÜÇØÇÝTËS :

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Colourless nucleated cells, and are of different types.

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Count: 6000-8000/mm³

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Formed in: Bone marrow, lymph glands, spleen.

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Average life span: Generally short lived (1-15 days).

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Function: Part of immune system.

TÝPËS ØF WBÇ: GRÅÑÜLØÇÝTËS & ÅGRÅÑÜLØÇÝTËS

1.

GRANULOCYTES : They are of 3 types:

(a) Neutrophils (Heterophils)

: 60-65%. Soldier of the body.

Function: Phagocytosis.

(b) Eosinophils (Acidophils) :

2-3%.

Resist

infections.

Cause allergic reactions

(c) Basophils

(Cyanophils):

0.5-1%. Secrete histamine,

serotonin,

heparin,

etc.

Cause

inflammatory

reactions.

2.

Agranulocytes They are of 2 types:

(a) Lymphocytes (20-25%) : Smallest WBC with largest nucleus.

Includes

B-lymphocytes

&

T-lymphocytes.

Cause

immune

responses. Secrete antibodies.

Leucocyte/white blood cell (WBC)

Granulocytes

Agranulocytes

Eosinophil

Neutrophil

Basophil

Monocyte

Lymphocyte

T cell

B cell