PRIMARY HEMOSTASIS

• Hemostasis


  is a complex physiologic process that keeps circulating blood in a fluid state and then, when an injury occurs, produces a clot to stop the bleeding, confines the clot to the site of injury, and finally dissolves the clot as the wound heals
• Hemorrhage


  Abnormal bleeding
• Thrombosis


  Pathological clotting
• Anatomic hemorrhage

  Chronic inflammation

  Transfusion dependence

  The absence of a single plasma procoagulant may destine the individual to lifelong
• Hemostasis


  involves the interaction of vasoconstriction, platelet adhesion and aggregation, and coagulation enzyme activation to stop bleeding
• Cells of the vascular intima

  Extravascular tissue factor (TF)- bearing cells

  Platelets


  Key cellular elements of hemostasis
• Coagulation and fibrinolytic proteins and their inhibitors

  Plasma components of hemostasis
• Primary hemostasis


  refers to the role of blood vessels and platelets in response to a vascular injury, or to the commonplace desquamation of dying or damaged endothelial cells.
• vasoconstriction and platelet plug formation


  comprise the initial, rapid, short-lived response to vessel damage
• Fibrin


  to control major bleeding in the long term, the plug must be reinforced by
• collagen abnormalities

  thrombocytopenia

  qualitative platelet disorders

  von Willebrand disease


  Defects in primary Hemostasis that can cause debilitating, sometimes fatal, chronic hemorrhage.
• Secondary hemostasis


  describes the activation of a series of coagulation proteins in the plasma, mostly serine proteases, to form a fibrin clot
• Thrombin


  an enzyme that converts fibrinogen to a localized fibrin clot
• Fibrinolysis


  The final event of hemostasis
• Fibrinolysis


  The gradual digestion and removal of the fibrin clot as healing occurs
• Vascular intima and platelets


  Associated with primary Hemostasis
• Coagulation and fibrinolysis


  Associated with secondary hemostasis
• Primary hemostasis


  Activated by desquamation and small injuries to blood vessels
• Primary Hemostasis


  Involves vascular intima and platelets
• Primary Hemostasis


  Rapid, short-lived response
• Primary Hemostasis


  Procoagulant substances exposed or released by damaged or activated endothelial cells
• Secondary Hemostasis


  Activated by large injuries to blood vessels and surrounding tissues
• Secondary Hemostasis


  Involves platelets and coagulation system
• Secondary Hemostasis


  Delayed, long-term response
• Secondary Hemostasis


  The activator, tissue factor, is exposed on cell membranes
• Vascular intima


  provides the interface between circulating blood and the body tissues
• Endothelial cells


  The innermost lining of blood vessels is a monolayer of metabolically active _________
• Endothelial cells


  are complex and heterogeneous and are distributed throughout the body
• Endothelial cells


  play essential roles in immune response, vascular permeability, proliferation, and, of course, hemostasis
• Endothelial cells


  form a smooth, unbroken surface that eases the fluid passage of blood
• Fibroblasts


  In all blood vessels, ___________ occupy the connective tissue layer and produce collagen
• Arteries and arterioles


  Smooth muscle cells in ________ and __________, but not in the walls of veins, venules, or capillaries, contract during primary hemostasis
• Inhibiting platelet aggregation

  Preventing coagulation activation and propagation

  Enhancing fibrinolysis


  Normally, the intact vascular endothelium prevents thrombosis by:
• Endothelial cells


  are rhomboid and contiguous, providing a smooth inner surface of the blood vessel that prevents harmful turbulence that otherwise may activate platelets and coagulation enzymes
• Endothelial cells


  form a physical barrier separating procoagulant proteins and platelets in blood from collagen and tissue factor
• Collagen


  In the internal elastic lamina Promotes platelet adhesion
• Tissue factor


  In fibroblasts and smooth muscle cells that activates coagulation
• Internal elastic lamina


  Collagen may be found in the?
• Fibroblasts and smooth muscle cells

  Tissue factor may be found in the?
• Endothelium


  Innermost vascular lining