platelet cytology
Last reviewed 01/2018
Platelets are disc-shaped and approximately 1-2 micrometers in diameter. Usually forming clumps of platelets, they stain pale blue with Romanowsky stains in blood smears.
Ultrastructurally, they have a very active cytoskeleton. Microfilaments participate in clot retraction while microtubules regulate the overall shape. Mitochondria are evident within the cytoplasm. They are bounded by a mucopolysaccharide outer membrane.
There are two types of granule: lysosomal alpha granules and dense granules. They contain substances vital to function e.g. :
- dense granules:
- ADP
- ATP
- serotonin, 5HT
- lysosomal granules:
- von Willebrand factor
- platelet-derived growth factor
- platelet activating factor
- factor V
- fibrinogen
- platelet factor 4