Final answer:
Thrombocytopenia and thrombocytosis are forms of hemostasis disorder that involve platelets, leading to either excessive bleeding or unwanted blood clot formation, respectively.
Step-by-step explanation:
The form of hemostasis disorder that involves platelets is thrombocytopenia and thrombocytosis. Thrombocytopenia is a condition where there is an insufficient number of platelets leading to a failure in blood clot formation and resulting in excessive bleeding, even from minor wounds. Conversely, thrombocytosis is characterized by an excessive number of platelets, which can lead to the formation of unwanted blood clots or thrombosis, and can be a potentially fatal disorder. Both conditions are serious and affect hemostasis, the process by which bleeding stops.