Myelopoiesis

Myelopoiesis

Phagocytes are specialized in destruction of foreign materials; thus they have a fundamental role in body s defense against invasion by micro-organisms, destruction of tumor cells and ingestion of apoptotic cells.
Phagocytes are classified into:

1. polymorph nuclear: neutrophils, eosinophils and basophils.
2. mononuclear: monocytes and macrophages.

Neutrophils:
• They are found in bone marrow, blood and tissues.
• They are the most numerous phagocytes as normal range is 2.5-7.5 ×109/L; constituting about 65% of circulating leukocytes in man.
• About 50% of neutrophils in blood marginate to the wall of vessels and they are not represented in blood count; demarginating in response to infection, exercise and steroid treatment.
• Their half life in blood is short about 12-24 hours; after that they enter tissues where die after 1-2 days.
• They are easily identified in blood smear when stained with Romanovsky stain by characteristic segmented nucleus and pale pink cytoplasm filled with indistinct violet colored granules.