− | Primary haemostasis is dependent on the activity of platelets and, to a lesser extent, the blood vessels themselves. Platelets are the smallest solid formed component of blood, and are non-nucleated, flattened disc-shaped structures<sup>1</sup>. Their activity leads to vascoconstriction and the formation of platelet plugs to occlude vessel defects. Platelets develop in the bone marrow, and have a life span of around 7.5 days. Around two thirds of platelets are found in the circulation at any one time, with the remainder residing in the spleen<sup>1</sup>. | + | Primary haemostasis is dependent on the activity of platelets and, to a lesser extent, the blood vessels themselves. [[Thrombocytes|Platelets]] are the smallest solid formed component of blood, and are non-nucleated, flattened disc-shaped structures<sup>1</sup>. Their activity leads to vascoconstriction and the formation of platelet plugs to occlude vessel defects. Platelets develop in the bone marrow, and have a life span of around 7.5 days. Around two thirds of platelets are found in the circulation at any one time, with the remainder residing in the spleen<sup>1</sup>. |
− | Apart from unusual cases involving vasculitis, there are two causes of defects in primary haemostasis: thrombocytopenia (reduced platelet number), or thrombocytopathia (defective platelet function)<sup>2</sup>. | + | Apart from unusual cases involving vasculitis, there are two causes of defects in primary haemostasis: [[Platelet_Abnormalities#Thrombocytopaenia|thrombocytopenia]] (reduced platelet number), or [[Platelet_Abnormalities#Thrombocytopathia|thrombocytopathia]] (defective platelet function)<sup>2</sup>. |