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[[Image:LH_Platelet_Histology.jpg|right|thumb|175px|<center><p>'''Platelets'''</p><sup>©RVC 2008</sup></center>]]
[[Image:LH_Platelet_Histology.jpg|right|thumb|175px|<center><p>'''Platelets'''</p><sup>©RVC 2008</sup></center>]]
==Introduction==
==Introduction==
[[Platelet|Platelets]] (or thrombocytes) are responsible for primary haemostasis by the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall. These breaches are then sealed more completely by the formation of a fibrin clot mediated by the coagulation factor cascade.
[[Platelet|Platelets]] (or thrombocytes) are responsible for primary haemostasis by the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall. These breaches are then sealed more completely by the formation of a fibrin clot induced by the coagulation factor cascade.
Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia'''). [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] (ITP) is one common cause of thrombocytopaenia and this may be a primary or secondary disease. '''Thrombocytosis''' refers to an increase in the blood platelet concentration above the normal level.
Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia'''). [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] (ITP) is one common cause of thrombocytopaenia and this may be a primary or secondary disease. '''Thrombocytosis''' refers to an increase in the blood platelet concentration above the normal level.
Thrombocytopaenia and thrombocytopathia lead to disorders of primary haemostasis but, in general, this is less serious than the disorders of secondary haemostasis caused by deficiencies in the [[Coagulation Factor Deficiency|coagulation factors]].
Thrombocytopaenia and thrombocytopathia lead to disorders of primary haemostasis but, in general, this is less serious than the disorders of secondary haemostasis caused by deficiencies in the [[Coagulation Factor Deficiency|coagulation factors]].
==Thrombocytopaenia==
==Thrombocytopaenia==