ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Medical Importance And General Considerations In Coagulation And Fibrinolysis

Updated on February 3, 2014

Coagulation Cascade



Nomenclature of the coagulation proteins has been accepted internationally and they are as follows:

  1. Factor I: Fibrinogen
  2. Factor II: Prothrombin
  3. Factor III: Tissue thromboplastin
  4. Factor IV: Calcium ions
  5. Factor V: Proaccelerin-labile factor
  6. Factor VII: Stable factor- Proconvertin
  7. Factor VIII: Antihemophilic globulin (AHG, AHF)
  8. Factor IX: Plasma thromboplastin component (PTC), Christmas factor
  9. Factor X: Stuart-Prower factor
  10. Factor XI: Plasma thromboplastin antecedent PTA
  11. Factor XII: Hageman factor
  12. Factor XIII: Fibrin stabilizing factor.

The numerical order does not represent the sequence of activation. In addition to the above, there are other recently described factors such as prekallikrein (PK) and high molecular weight kininogen (Kin) which are involved in the activation of factor XII and XI respectively, in the intrinsic pathway. The activated factors are represented with the suffix ‘a’.

All the coagulation proteins except factor VIII: C are synthesized mainly in the liver. Endothelial cells including those of hepatic blood vessels secrete factor VIII:vWF polymers. Factor VIII:C molecules form ionic bonds with factor VIII:vWF polymers which provide a carrier for them in the circulation and also prevents their destruction. Factors II, VII, IX and X are produced in the liver and these are termed vitamin- K dependent factors, since this vitamin is necessary for making them functional. Thrombin is produced from prothrombin and it converts soluble fibrinogen to fibrin which consists of insoluble polymers. Thrombin can be produced through two different reaction sequence- the intrinsic and extrinsic pathways.

The Intrinsic Pathway


Intrinsic pathways

All necessary components for this pathway are present in circulating blood. This pathway is initiated by the absorption of factor XII (Hageman factor) and kininogen with bound prekallikrein and factor XI to negatively charged subendothelial surfaces, exposed during vascular injury. There after successive activation of factors occurs in a sequential manner. Factors XIIa activates IX to IXa. Activated form of factor VIII:C interacts with factor IXa bound to platelets on their surface. In association with activated factor VIII:C, factor IXa optimally activated and cleaves platelet bound factor X to Xa. Factor Va molecules that have been either adsorbed from plasma and then activated by a platelet protease or released in activated form from platelet alpha granules. This factor Xa-Va complex is adjacent to platelet bound prothrombin molecules. Factor Xa in this complex cleaves the prothrombin molecule into two portions, one part of which is thrombin. Thrombin causes local platelet aggregation and also leads to formation of fibrin monomers from fibrinogen. It also cleaves and activates factor XIII, and this covalently links fibrin monomers into polymers enxymically. Calcium (factor IV) is required at various steps of the whole process.

The Extrinsic Coagulation Pathway


The extrinsic pathway

This is initiated by the entry of phospholipoprotein surface and organelle membranes from disrupted tissue cells. Factor VII is bound to these membranes and activated to factor VIIa. Factor VIIa activates factor X on the surface of the organelle membranes. Attachment of factor V and prothrombin and subsequent thrombin generation occur similar to that described for the intrinsic mechanism. Normally, the extrinsic and intrinsic mechanisms are complementary to each other, the former being more rapid in action. They are all confined to the local site of injury.

Thrombin cleaves fibrinogen molecule to release fibrinopeptides (fibrin monomers) which bind to form fragile polymers. Thrombin activates factor XIII to factor XIIIa which enzymatically converts fibrin monomers into stable polymers which form the insoluble fibrin clot. Polymerisation of fibrin is limited by the inhibition of factors XIIa, Xia, IXa and Xa and thrombin by anti-thrombin III (heparin cofactor) present in blood and endothelial cell surfaces. Another inhibitor is protein C which is a vitamin K dependent enzyme also present in blood and on endothelial cell surfaces. Protein C, after activation by thrombin, also cleaves and eliminates the activated forms of factor VIII:C and factor V. Deficiency of antithrombin III leads to thrombotic tendencies.




This is the process by which fibrin polymers are lysed by the enzyme plasmin derived by partial proteolysis of the zymogen-plasminogen, which is adsorbed to fibrin polymers. Plasminogen activators are divided from the lysosomes of disrupted endothelial and tissue cells. These bind to fibrin polymers and converts firbin-bound plasminogen into plasmin. Plasmin remains bound to fibrinogen and degrades it into soluble fragments- the fibrin degradation products (FDP). In addition to splitting fibrin, plasmin is also capable of splitting fibrinogen and factor V and VIII:C. Activity of plasmin is inhibited by normal inhibitors. These are alpha, antiplasmin which is a rapid inactivator, alpha2-macroglobulin which is a slow inactivator and anti-thrombin. Antithrombin rapidly inactivated plasmin in the presence of heparin.

© 2014 Funom Theophilus Makama


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)