Coagulation Pathways: Intrinsic and Extrinsic Pathways

 Intrinsic Pathway Extrinsic Pathway  (1-6 minutes) (15 seconds) Tissue factor factor III Ca ++ VIIa VII stable fibrin polymer fibrinogen fibrin (monomer polymer) XIIIa XIII X thrombin prothrombin Xa Ca ++ pf3 V X IXa pf3 Ca ++ VIII IX XI XIa XIIa collagen XII 2

 Intrinsic Pathway Extrinsic Pathway  (1-6 minutes) (15 seconds) Tissue factor factor III Ca ++ VIIa VII stable fibrin polymer fibrinogen fibrin (monomer polymer) XIIIa XIII X thrombin prothrombin Xa Ca ++ pf3 V X IXa pf3 Ca ++ VIII IX XI XIa XIIa collagen XII 3

Assessment of hemostatic function • Bleeding time • Clotting time 4

Bleeding Time • Definition: • It is the time required to stop bleeding from injured blood vessel by platelet plug formation. • Injury VC then Platelet plug formation. So, it assess both vascular wall integrity, andplatelets ( number and function).Done by filter paper 5

Bleeding time 6

Bleeding time = No. of Drops/ 4 7

Bleeding time • Normal Value: 1: 3 min • Prolonged in: 1- Vessel wall defect e.g. Scurvy.2- Platelet defect e.g. PurpuraQuantitative defect (Thrombocytopenia,i.e decrease no. )Qualitative defect (Thrombocytopathia,i.e decrease function). 8

Clotting time • Definition: It is the time required to stop bleedingfrom injured blood vessel by fibrin clotformation. • So, it assess clotting factors fibrin clot formation. • Done by Non-Heparinized capillary tube 9

Clotting time 10

Clotting time (capillary tube test) 11

Fibrin thread 12

Clotting time • Normal Value: 3 -10 min. • Prolonged in: Clotting factors deficiency:1- Congenital (hemophilia): • A, B, C 2- Acquired (Vit K deficiency): • Sterile intestine by long treatment with antibiotics. • Fat malabsorption. • Liver disease. 13

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