White blood cells (leukocytes)

 

  • Mobile units of the body's defense system
  • Typical concentration is 5,000 - 9,000 per cubic millimete
  • Types of WBCs:
o Polymorphonuclear cells (granulocytes) include:
- neutrophils (50 - 70% of WBCs)
- eosinophils (1 - 4%)
- basophils (less than 1%)
o lymphocytes (25 - 40%)
o monocytes (2 - 8%)
o megakaryocytes (only present in the bone marrow - give rise to platelets)
  • Some formed in the bone marrow (polymorphonuclear cells) others in the lymphatic system mostly the lymph nodes (lymphocytes and monocytes)