Primary hemostasis is the first phase in the hemostasis process that stops bleeding. After vasoconstriction reduces blood flow, primary hemostasis begins, which is then followed by secondary hemostasis. Primary hemostasis is the action by platelets taken on at the site of a vascular breach, which adhere to the damaged wall and secrete substances for the formation of a blood mass, called a platelet plug or white thrombus. This patch is temporary and will be replaced by a clot during the coagulation itself, in the stage of secondary hemostasis. Primary hemostasis is considered the bleeding time, which appears increased in the case of a pathology. Diseases such as platelet thrombocytopenia (deficiency) or platelet disorders (abnormal operation) and von Willebrand disease, factor into this process and are the main diseases of primary hemostasis .