LEUKOCYTES
(White Blood Cells)
Classes
• 2 main classes:
• Granulocytes – have a grainy cytoplasm
• Agranulocytes – have a clear cytoplasm
Types
There are 5 types of white blood cells:
Granulocytes
• Neutrophils
40-75%
• Eosinophils
5%
• Basophils
0.5%
Agranulocytes
• Lymphocytes 20-50%
• Monocytes
1-5%
The range is because the requirement for
different types of WBCs vary from time to time.
Neutrophils
Structure:
• Multilobed nucleus
• Inconspicuous granules
Amount:
• 3-7,000/mm³
Functions:
• Engulfing bacteria & viruses
(phagocytosis)
Life Span:
• hours → days
Eosinophils
Structure:
• Bilobed nucleus
• Large, red granules
Amount:
• 100-400/mm³
Functions:
• phagocytosis
• Protects against parasitic infections
• Neutralize histamines (their amts. incr. during
hay fever & allergy attacks)
Life Span – hours → days
Basophils
Structure:
• Lobed nucleus
• Large granules, but fewer
Amount:
• 20-50/mm³
Functions:
• Become mast cells when they leave b.v. & produce
histamines
• Respond to allergens rapidly (anaphylactic shock)
• Produce heparin (anticoagulant)
Life Span – hours → days
Monocytes
Structure:
• Largest WBC
• U-shaped nucleus
• Grayish blue cytoplasm
Amount:
• 100-700/mm³
Functions:
• Phagocytosis
• Become macrophages & remove dead cells
Life Span – weeks → months
Lymphocytes
Structure:
• Most numerous in children;
2nd most in adults
• Spherical nucleus
• Small “ring”of cytoplasm; pale blue
Amount:
• 1500-3000/mm³
Functions:
• T cells – attack foreign antigens directly
• B cells – produce antibodies for immunity
Life Span – months → lifetime
White Blood Cell Count
• Normal adult has 5,000-10,000 cells/mm3
• Leukocytosis- WBC count above 10,000
cells/mm3
– Can be a sign of acute infection
– Occurs during times of stress and vigorous
exercise.
• Leukopenia- WBC below above 10,000
cells/mm3
– Can be a sign of virus such as influenza,
measles, mumps and HIV