== Blood Smears ==

Examine slide 37. This is a blood smear stained with Wright’s stain. Wright’s stain is a polychrome stain in wide use for fixing as well as staining smears of blood as well as exudates and protozoan parasites. Its staining action depends upon a combination of methylene blue and eosin, which stain both independently as well as synergistically. The solution thus contains three staining factors that color the various structures of the preparation selectively.

The basophilic staining central region of a platelet is called the granulomere or chromomere because the cytoplasm here contains more granules and organelles than the peripheral cytoplasm, which is pale and homogenous. This thin peripheral zone of cytoplasm is called the hyalomere. It stains a pale blue. The characteristic granules of human platelets, called alpha granules, are approximately 0.2μm in diameter. The currently known list of alpha-granular proteins continues to enlarge and includes many adhesive proteins (e.g. Fg, von Willebrand factor (vWf) and thrombospodin (TSP)), plasma proteins (e.g. IgG and albumin), cellular mitogens (e.g. platelet derived growth factor and TGF beta), coagulation factors (e.g. factor V) and protease inhibitors (e.g. alpha 2-macroglobulin and alpha 2-antiplasmin). More recently the inner lining of the alpha-granule unit membrane has been demonstrated to contain a number of physiologically important receptors including glycoprotein IIb/IIIa (alpha IIb beta 3) and P-selectin.

On slide 8, Intervertebral disc (H&E) find the red bone marrow and identify the megakaryocytes from which platelets are derived. Megakaryocytes are the largest cells found in normal bone marrow. The nucleus is multilobed and polyploid since chromosomal replications occur in these cells without cytoplasmic divisions.