Overview of Hemostasis and Coagulation Lecture Notes PDF

Overview of hemostasis and coagulation Presented by Dr. Sahar Gamal Elbager Assistant Professor of Haematology UMST  Definition It is a phenomenon which is responsible to keep the blood in fluid state in the circula...

Overview of hemostasis and coagulation Presented by Dr. Sahar Gamal Elbager Assistant Professor of Haematology UMST  Definition It is a phenomenon which is responsible to keep the blood in fluid state in the circulation as well as to arrest bleeding followed by an injury to blood vessel. Dr. Sahar Elbager  Haemostasis (physiology) Function of haemostatic mechanisms - Prevent blood loss from intact vessels. - Stop excessive bleeding from injured vessels. - Insure removal of plug when heeling is complete. Dr. Sahar Elbager  Steps of Hemostasis Hemostasis can be divided into three categories: 1. Primary hemostasis: This is defined as the formation of the platelet plug with vasoconstriction. 2. Secondary hemostasis: This is defined as the formation of fibrin through the coagulation cascade. 3. Tertiary hemostasis: This is defined as the formation of plasmin for breakdown of the clot. Dr. Sahar Elbager  Primary Hemostasis Primary Haemostasis involves 1. Blood vessels (vascular vasoconstriction phase and release of tissue or exogenous factors) Vasoconstriction reduce blood flow through an injured area. 2. Thrombocytes (adhesion, aggregation, and secretion or release of platelate factors) After 3 to 5 minutes , blood flow is arrested with the formation of a platelet plug 3. Platelet plug temporarily arrests bleeding Dr. Sahar Elbager Primary Hemostasis Dr. Sahar Elbager  Secondary Hemostasis Secondary Hemostasis involves `1. Plasma coagulation factors 2.Tissue factor Provides for definitive hemostasis Takes 5 to 10 minutes by formation of fibrin Reinforces the platelet plug. Dr. Sahar Elbager Secondary Hemostasis Dr. Sahar Elbager  Plasma coagulation factors 1. The intrinsic pathway 2. The extrinsic pathway 3. The common pathway Dr. Sahar Elbager Coagulation-pathways Dr. Sahar Elbager  Tertiary hemostasis Tertiary haemostasis-Fibrinolysis Essential final step in any hemostasis mechanism. Enabling in 48 to 72 hours, and a return to normal by breakdown of the clot fibrin (by of plasmin) and healing the injured vessel. Dr. Sahar Elbager Dr. Sahar Elbager Thank you Dr. Sahar Elbager