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Jul 17, 2023 · Learn how the extrinsic and intrinsic pathways of coagulation are triggered by different types of injury and lead to the formation of a blood clot. Find out how the common pathway, regulation and fibrinolysis are involved in haemostasis and bleeding disorders.
- Introduction
- The Extrinsic Pathway
- The Common Pathway
- The Intrinsic Pathway
- Regulating The Coagulation Cascade
- Coagulation Screening
- Dysfunction of The Coagulation Cascade
- Key Points
- References
- GeneratedCaptionsTabForHeroSec
The coagulation cascade is a series of reactions, catalysed by protein enzymes known as coagulation ‘factors’. When activated, these factors trigger the conversion of other factors in the coagulation cascade resulting in secondary haemostasis. Secondary haemostasis refers to the stabilisation of activated platelets due to the actions of strands of ...
Initiation of the coagulation cascade is usually mediated by tissue factor via the extrinsic pathway. Tissue factor is expressed on the surface of many cells found outside blood vessels but not on the surface of circulating blood cells or the endothelium. When the endothelium is damaged, tissue factor comes into contact with blood and combines with...
The common pathway begins with activation of factor X (to factor Xa) via either the extrinsic pathway or the intrinsic pathway. It is the final stage of the coagulation cascade and leads to the formation of thrombin and fibrin. Factor Xa combines with factor V, platelet membrane phospholipids and Ca2+ ions to convert prothrombin into thrombin. Thro...
The intrinsic pathway can be activated by surface contact, when damage to the vascular endothelium leads to exposure of clotting factors to negatively charged subendothelial surfaces, mediated by the molecule Kallikrein. Within blood vessels, thrombin generated from previous activation of the extrinsic pathway also activates the intrinsic pathway. ...
Without regulatory mechanisms, the positive feedback looptriggered by thrombin in the intrinsic pathway would continue indefinitely and cause dangerous levels of clotting in the blood. For this reason, various proteinsinhibit aspects of the coagulation cascadeonce enough thrombin has been produced. Protein C is produced in response to thrombin bind...
Multiple tests exist to assess haemostasis. They involve adding triggers to a sample of reversibly anticoagulated plasma (by citrate) and measuring the time taken for fibrin to form. The two most frequently performed tests are the prothrombin time (PT) and the activated partial thromboplastin time(APTT). For more information on interpreting these t...
Dysfunction of the coagulation cascade can be caused by several medical conditions: 1. Haemophiliais a congenital deficiency in either factor VIII (haemophilia A), factor IX (haemophilia B) or factor XI (haemophilia C) leading to defective clotting and therefore a tendency to bleed. 2. Chronic liver disease can lead to defective coagulation as many...
The coagulation cascade is one of the key components in the cessation of bleeding (haemostasis), by generating afibrin meshthat stabilises activated plateletsTwo pathways (the extrinsic and intrinsic) both result in the activation of factor X, which leads to the conversion of prothrombin into thrombinThrombin converts fibrinogen into fibrinand triggers the activation of factor XIII to cross-link the fibrin strands and stabilise the clotA stable clotis formed by activated platelets, fibrin and factor XIIIaHoffbrand A. V., Moss P. A. H., 2011., Essential Haematology, 6thEdition, John Wiley & Sons, New YorkRalston S. H., et al., 2018., Davidsons Principles and Practice of Medicine, 23rdEdition, Elsevier, EdinburghNaish J., Syndercombe Court D., 2019., Medical Sciences, 3rdEdition, Elsevier, EdinburghHall J. E., Hall M. E., 2021., Guyton and Hall Textbook of Medical Physiology, 14thEdition, Elsevier, EdinburghLearn how the coagulation cascade is divided into three pathways: intrinsic, extrinsic and common. Understand the role of coagulation factors, thrombin, fibrin and regulation of clot formation.
- Ewan Evans
Nov 8, 2021 · Learn how the coagulation cascade forms a blood clot after injury by activating three pathways: extrinsic, intrinsic, and common. The extrinsic pathway is initiated by tissue factor, while the intrinsic pathway is activated by factors in the blood.
- What is the coagulation cascade?The coagulation cascade, or secondary hemostasis, is a series of steps in response to bleeding caused by tissue injury, where each step activates t...
- When is fibrin produced during the coagulation cascade?Fibrin (factor Ia) is a long, thin protein with branches produced at the end of the coagulation cascade when fibrinogen (factor I) is converted to...
- What is the main goal of coagulation?The main goal of coagulation is to form a stable blood clot to stop bleeding and allow time for the tissue to be repaired.
- What are coagulation disorders?Coagulation disorders are disorders which affect the coagulation cascade and can either cause excessive or inadequate clotting. Coagulation disorde...
- What are the most important facts to know about the coagulation cascade?The coagulation cascade refers to the series of steps that occur during the formation of a blood clot after injury by activating a cascade of prote...
Feb 24, 2023 · Within primary and secondary hemostasis, 3 coagulation pathways exist: intrinsic, extrinsic, and common. [1] [2] [3] [4] Pathways. The intrinsic pathway responds to spontaneous, internal damage of the vascular endothelium, whereas the extrinsic pathway becomes activated secondary to external trauma.
- Walker Barmore, Tanvir Bajwa, Bracken Burns
- 2023/02/24
- 2018
Learn how the body seals a ruptured blood vessel and prevents further loss of blood through hemostasis, the process of vascular spasm, platelet plug formation, and coagulation. The extrinsic and intrinsic pathways are two of the three pathways of coagulation, which involve different clotting factors and are triggered by different stimuli.
- Lindsay M. Biga, Sierra Dawson, Amy Harwell, Robin Hopkins, Joel Kaufmann, Mike LeMaster, Philip Mat...
- 2019
This web page is part of a free textbook on anatomy and physiology, but it has a glitch and cannot be accessed. It covers the extrinsic and intrinsic pathway of coagulation, which are involved in blood clotting.
A schematic overview of the intrinsic and extrinsic pathways of coagulation. Dotted lines represent proposed amplificatory pathways that involve crosstalk between components of the extrinsic or common pathway and the intrinsic pathway. αKK indicates α-kallikrein; F, factor; HK, high molecular weight kininogen; and TF, tissue factor.
