Hemostatic plug

Formation of a fibrin mesh that binds to the platelet aggregate, forming a more stable hemostatic plug or thrombus. 

Partial or complete dissolution of the hemostatic plug or thrombus by plasmin. 

Platelet aggregation. Clumping together of platelets as part of a sequential mechanism leading to the initiation and formation of a thrombus or hemostatic plug. 

Platelets provide the initial hemostatic plug at sites of vascular injury. They also participate in reactions that lead to atherosclerosis and pathological thrombosis. Antagonists of platelet function have thus been used in attempts to prevent thrombosis and to alter the natural history of atherosclerotic vascular disease. 

Platelet participation in normal hemostasis. The hemostatic plug is the specific response to external vessel lesion and depends on the extent of vessel wall damage, the specific interaction between endothelial cells and activated platelets, release of the contents of platelets intracellular granules in response to activation, the conjoint activity of activated factor Vll and platelet agonists, and the open conditions of blood flow. After activation, platelets also produce the external ization of membrane phosphatidylserine through the flip-flop mechanism that will support the function of the prothrombinase complex ending in thrombin generation and local clot formation. 

Role of fibrin Local stimulation of the coagulation cascade by factors released from the injured tissue and platelets results in the formation of thrombin (Factor II). In turn, thrombin, a serine protease, catalyzes the conversion of fibrinogen to fibrin, which is incorporated into the plug. Subsequent cross-linking of the fibrin strands stabilizes the clot and forms a hemostatic plug. 

Degradation of an unwanted thrombus and a beneficial hemostatic plug by plasminogen activators. 

The damage of a blood vessel results in the formation of a hemostatic plug, which is achieved by several differ-entmechanisms including vascular spasm, formation of a platelet plug, blood coagulation, and growth of fibrous tissue into the blood clot. 

Arteries are punctured with a hypodermic needle (25 gauge 16 x 5/10 mm). The bleeding time of the mesenteric blood vessels is observed through a microscope at a magnification of 40 x. The time in seconds is determined from the puncturing until the bleeding is arrested by a hemostatic plug. 

The most important physiological function of the blood platelets consists in their participation in the mechanisms leading to the arrest of hemorrhage. Bleeding from smaller vessels, such as the arterioles and venules, is almost exclusively arrested by means of the formation of a hemostatic plug which is composed of densely packed blood platelets. In larger... 

Hugues (1959), in particular, was able to show convincingly that the formation of an efficient hemostatic plug consists of three phases (1) adherence of the platelets to the injured endothelium (2) growth of a loose aggregate of platelets by the addition of new platelets, (3) consolidation of this aggregate to a stable and impermeable hemostatic plug. 

Sixma JJ, Wester J. The hemostatic plug. Semin Hematol 1977 14 265-88... 

Adhesion of platelets onto a damaged vascular sur ce is the primary event in the formaticHi ofd hemostatic plug. For perfect hemostatic performance, this initial adhesion step should be followed by further deposition of platelets onto the initial adherent layer rmtil an effective microthrombi is formed at the site of damage. Formation of s hemostatic plug is the result of a well recognized series of interactions among platelet glycoproteins, plasma adhesive proteins and components of the subendothelium. 

Formation of a hemostatic plug or a red thrombosis (fibrin and entrapped red blood cells) at a site at which there is no injury produces occlusion. Death to the surrounding tissues can occur (infarction), or pieces of the thrombus may be tom away and moved to the lungs, producing pulmonary embolism. Such dysfunction of the hemostatic system is generally not attributable to a single cause. For example, heterozygous individuals with half of the normal amount of protein C do not necessarily present with... 

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