HEAMOSTASIS & FIBRINOLYSIS HEAMOSTASIS & FIBRINOLYSIS 1 HAEMOSTASIS & FIBRINOLYSIS HAEMOSTASIS & FIBRINOLYSIS DR B L Mtinangi DR B L Mtinangi DEPARTMENT OF PHYSIOLOGY DEPARTMENT OF PHYSIOLOGY Hubert Kairuki Memorial Hubert Kairuki Memorial University University December 3, 2015 December 3, 2015
26
Embed
HEAMOSTASIS & FIBRINOLYSIS 1 HAEMOSTASIS & FIBRINOLYSIS DR B L Mtinangi DEPARTMENT OF PHYSIOLOGY Hubert Kairuki Memorial University December 3, 2015.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
HAEMOSTATISHAEMOSTATISHaemostasis is prevention of blood Haemostasis is prevention of blood loss after rupture or injury/trauma of loss after rupture or injury/trauma of blood vesselsblood vesselsIt is achieved through: It is achieved through: – Vascular spasmsVascular spasms– Formation of platelet plug formationFormation of platelet plug formation– Blood coagulation i.e. Development of Blood coagulation i.e. Development of
Vascular spasms is due to:Vascular spasms is due to:– Nervious reflex due to painNervious reflex due to pain– Effects of local and humoral mechanismEffects of local and humoral mechanism– Thromboxane A2 (prostaglandin) cause Thromboxane A2 (prostaglandin) cause
vasoconstritionvasoconstrition
All generate an Action Potential and All generate an Action Potential and cause Myogenic spasm cause Myogenic spasm (constriction) and REDUCE blood (constriction) and REDUCE blood flowflow
The spasm last less than 1 minThe spasm last less than 1 min
FORMATION OF PLATELET PLUGFORMATION OF PLATELET PLUGInitiated when the platelet come into Initiated when the platelet come into contact with damaged vascular surface or contact with damaged vascular surface or collagen fiberscollagen fibers
Platelets adhere and aggregate to the Platelets adhere and aggregate to the damaged sitedamaged site
Platelets secrete large quantity of ADP and Platelets secrete large quantity of ADP and Thromboxane A2 (prostaglandin) Thromboxane A2 (prostaglandin)
Endothetal cells secrete a Von Willebrands Endothetal cells secrete a Von Willebrands factor (a small protein molecule)factor (a small protein molecule)– Usually attached to factor VIIIUsually attached to factor VIII– Bridges the platelets to exposed collagenBridges the platelets to exposed collagen
Plasma thromboplastin antecedent Plasma thromboplastin antecedent PTA: factor XIPTA: factor XI Hegman factor XII (Hegman factor XII (contact factor)contact factor)
Fibrin stabilizing: factor XIIIFibrin stabilizing: factor XIII
NB: Factor II, VII, IX & X requires vit NB: Factor II, VII, IX & X requires vit K for their synthesis IN THE LIVER, K for their synthesis IN THE LIVER, thereforetherefore
Vit K deficiency & liver diseases leads Vit K deficiency & liver diseases leads to bleeding tendenciesto bleeding tendencies
COAGULATION is also regulated by several COAGULATION is also regulated by several natural anticoagulantsnatural anticoagulantsAntithrombin III inactivate coagulation Antithrombin III inactivate coagulation factors& it neutralizes thrombinfactors& it neutralizes thrombinAntithrombin III activity is enhanced by Antithrombin III activity is enhanced by heparinheparinProtein C receptor combine Protein C receptor combine thrombomodulin – inhibits thrombin and thrombomodulin – inhibits thrombin and several coagulation factorsseveral coagulation factorsProtein S accelerate the action of protein CProtein S accelerate the action of protein CDeficiency of the above factors leads to Deficiency of the above factors leads to HYPERCOAGULOPATHY states leading to HYPERCOAGULOPATHY states leading to increased THROMBOEMBOLISMincreased THROMBOEMBOLISM
Dissolution of a blood clot begins Dissolution of a blood clot begins shortly after its formationshortly after its formation
Plasma – contains a globulin Plasma – contains a globulin PLASMINOGEN incooperated in a large PLASMINOGEN incooperated in a large amount in the CLOTamount in the CLOT
PLASMINOGEN is activated byPLASMINOGEN is activated by Thrombin, factor XIII, and some lysosomal Thrombin, factor XIII, and some lysosomal
enzymes to PLASMIN with A PROTEOLYTIC enzymes to PLASMIN with A PROTEOLYTIC like actionlike action
PLASMINPLASMINPlasmin digest formed fibrin thread/clotPlasmin digest formed fibrin thread/clot
(FIBRINOLYSIS)(FIBRINOLYSIS)Plasmin also digest a number of clotting Plasmin also digest a number of clotting factors like Factor I, II, V & VIIfactors like Factor I, II, V & VIIalpha2 antiplasmin is always present in blood alpha2 antiplasmin is always present in blood whichwhichBinds with plasmin and inhibit its actionBinds with plasmin and inhibit its actionFibrinolysis system is therefore important for Fibrinolysis system is therefore important for removing small clot from tiny peripheral removing small clot from tiny peripheral vessels-preventing occlusion or blockage and vessels-preventing occlusion or blockage and thromboembolismthromboembolism