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)