Intrinsic And Extrinsic Pathway Of Blood Clotting Pdf

intrinsic and extrinsic pathway of blood clotting pdf

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All the components necessary for the clotting process to proceed are found in the blood.

When platelets are activated, they acquire enhanced capacity to catalyze interaction between activated coagulation on factors [Hirsh J, et al, ].

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Coagulation is the process by which a blood clot forms to reduce blood loss after damage to a blood vessel. Several components of the coagulation cascade, including both cellular e. The role of the cellular and protein components can be categorized as primary hemostasis the platelet plug and secondary hemostasis the coagulation cascade. The coagulation cascade is classically divided into three pathways: the contact also known as the intrinsic pathway, the tissue factor also known as the extrinsic pathway , and the common pathway. Both the contact pathway and the tissue factor feed into and activate the common pathway. Hemostasis can either be primary or secondary. Primary hemostasis refers to platelet plug formation, which forms the primary clot.

The Blood Coagulation Process. Coagulation can be initiated by either of two distinct pathways. Regardless of whether the Extrinsic or Intrinsic pathway starts coagulation, completion of the process follows a common pathway. Both pathways are required for normal hemostasis and there are positive feedback loops between the two pathways that amplify reactions to produce enough fibrin to form a lifesaving plug. Deficiencies or abnormalities in any one factor can slow the overall process, increasing the risk of hemorrhage. The coagulation factors are numbered in the order of their discovery. There are 13 numerals but only 12 factors.

16.5D: Coagulation

Coagulation clotting is the process by which blood changes from a liquid to a gel, forming a clot. It potentially results in hemostasis , the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion, and aggregation of platelets along with deposition and maturation of fibrin. Disorders of coagulation can result in bleeding hemorrhage or bruising or obstructive clotting thrombosis. The coagulation cascade of secondary hemostasis has two initial pathways which lead to fibrin formation:. The primary pathway for the initiation of blood coagulation is the tissue factor extrinsic pathway. The pathways are a series of reactions, in which a zymogen inactive enzyme precursor of a serine protease and its glycoprotein co-factor are activated to become active components that then catalyze the next reaction in the cascade, ultimately resulting in cross-linked fibrin.

Factor VII, the protease that initiates the normal blood clotting cascade, circulates in the blood in both its proenzyme factor VII and its activated factor VIIa forms. No clotting occurs, however, because neither form of the protein has any catalytic activity when free in solution. Blood clotting is normally initiated when tissue factor TF , an intrinsic plasma membrane protein, is exposed to the blood by injury to the wall of a blood vessel. TF is then able to bind factor VIIa from plasma, and possibly also factor VII, to form complexes capable of catalyzing the conversion of factor X, from plasma, into its activated form, factor Xa. Factor Xa catalyzes the conversion of additional factor VII molecules to their activated form, increasing the amount of tissue factor:factor VIIa complex available at the site of injury, accelerating the generation of factor Xa, and allowing the activation of factor IXa as well.

Coagulation , also known as clotting , is the process by which blood changes from a liquid to a gel , forming a blood clot. It potentially results in hemostasis , the cessation of blood loss from a damaged vessel, followed by repair. The mechanism of coagulation involves activation, adhesion and aggregation of platelets , as well as deposition and maturation of fibrin. Coagulation begins almost instantly after an injury to the endothelium lining a blood vessel. Exposure of blood to the subendothelial space initiates two processes: changes in platelets, and the exposure of subendothelial tissue factor to plasma factor VII , which ultimately leads to cross-linked fibrin formation.

Blood Coagulation. Blood clot. Blood Vessel Damage. Wound Healing. Activated. Platelets. Fibrin clot. RBC. WBC. Extrinsic Pathway. Intrinsic Pathway.


Negreva, K. Vitlianova, R. Background: Clinical interest in the haemostasis profile of patients with paroxysmal atrial fibrillation PAF , and in particular, in blood coagulation is significant. It is known that blood coagulation is activated in two pathways: extrinsic and intrinsic.

Intrinsic pathway of blood coagulation

Blood coagulation refers to the process of forming a clot to stop bleeding.

Key Points

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The coagulation pathway is a cascade of events that leads to Two paths, intrinsic and extrinsic, originate separately but converge at a specific.



Platelets are key players in hemostasis , the process by which the body seals a ruptured blood vessel and prevents further loss of blood.