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White Blood Cells (Leukocytes)

Structure

• Count 4000 – 8000 per mm³
• Have nucleus, amoeboid in shape.
• Increase in the number of WBCs at the cost of RBCs is called Leukemia.
• Abnormal decrease in the number of WBCs is called Leukopenia.

Production & death

• Produced in red bone marrow, lymph nodes & some time in liver & spleen.
• Average life about 2 weeks.
• Destroyed in the same manner as RBCs.
• Some (Neutrophils) live for only a few hours & 125 billion neutrophils produced each day.

Function

• Phagocytosis – Engulfing bacteria a defensive mechanism against bacteria.
• Inflammation – Reaction of tissue to injury to localize invasion of germs such as local
  heat, redness, swelling, pain etc.
• Formation of antibody – Kill germs or poisons from them (vaccination) by the
  production of antitoxins.

Special features

• Diapedesis – WBCs can squeeze out through walls of the capillaries to injured tissue to
  fight against disease causing germs & also destroy damaged cells.
• Pus cells are manly WBCs with tissue cells destroyed by the bacteria.
• Better known as white cells not white blood cells because spend most of their time in tissue
  fluid & lymph (90%)& a very little time in blood (10 %)
• Abnormal increase in number of WBCs (50,000 per mm³⁾ indicates an infection in the body.