Platelets are cytoplasmic fragments from megakaryocytes.
Their size varies between 1-4 µm. In non-anticoagulated, native blood, e.g., in capillary puncture, the platelets aggregate into small plugs. However, in EDTA blood they are seen most often individually.
The normal range is to x 109/L. Values below the norm are referred to as thrombocytopenia, and values above the norm are referred to as thrombocytosis.
Platelets participate significantly in hemostasis. Along with the vessels (vasoconstriction), they are responsible for primary hemostasis.