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Coagulation

General

Normal hemostasis


Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 9 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.

General
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● Primary hemostasis: initial step of forming platelet plug to stop bleeding from damaged vessel
● Secondary hemostasis: platelet plug is reinforced by fibrin clot; then fibrin clot is stabilized by activated factor XIII, which cross-links fibrin strands
● Tertiary hemostasis: as fibrin clot is formed, plasmin is generated to break down the clot
● Fibrin clot may occur via intrinsic or extrinsic pathway or both; in vivo it occurs via a hybrid model

Coagulation factors
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● Coagulation factors in intrinsic or extrinsic pathway assemble on surface of activated platelets, which are usually at site of vascular injury

Many coagulation reactions also require calcium as a cofactor:
Note: “a” after factor number indicates “activated”
      ● Factor I: fibrinogen
      ● Factor II: prothrombin
      ● Factor III: tissue thromboplastin (tissue factor and phospholipid)
      ● Factor IV: ionized calcium
      ● Factor V: occasionally called labile factor or proaccelerin
      ● Factor VI: unassigned originally called accelerin later discovered to be activated Factor V
      ● Factor VII: occasionally called stable factor or proconvertin
      ● Factor VIII: antihemophilic factor
      ● Factor IX: plasma thromboplastin component, Christmas factor
      ● Factor X: occasionally called Stuart-Prower factor
      ● Factor XI: occasionally called plasma thromboplastin antecedent
      ● Factor XII: Hageman factor
      ● Factor XIII: fibrin-stabilizing factor
      ● High Molecular Weight Kininogen: occasionally called Fitzgerald factor
      ● Prekallikrein: occasionally called Fletcher factor

Diagrams
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Coagulation


Intrinsic, common, and extrinsic pathways; chart credit to Kendall Crookston, M.D., PhD


The in vivo coagulation cascade; chart credit to Kendall Crookston, M.D., PhD

Additional references
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Chandler WI (2005). Physiology of hemostasis. In B Spiess, R Spence, A Shander (Eds), Perioperative Transfusion Medicine (pp 77-92). Lippincott, Williams, & Wilkins.

End of Coagulation > General > Normal hemostasis


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