Summary
Intrinsic and extrinsic coagulation pathways converge to convert fibrinogen to fibrin.
In depth
The intrinsic pathway is triggered by contact with collagen, the extrinsic by tissue factor. Both activate factor X; thrombin amplifies. Anticoagulants such as antithrombin limit clotting; plasmin dissolves clots. Balance prevents bleeding and thrombosis.
Coagulation factors are mostly made by the liver. Deficiencies cause bleeding disorders. Heparin potentiates antithrombin.
Example: haemophilia A lacks factor VIII.
The classical model has the intrinsic (contact activation, factors XII, XI, IX, VIII) and extrinsic (tissue factor, VII) pathways converging on factor X, then the common pathway (Xa with Va converts prothrombin to thrombin; fibrinogen to fibrin). In vivo the cell-based model is used: initiation on tissue factor-bearing cells, amplification on platelets, and propagation on activated platelet surfaces with a thrombin burst. Tests: PT (extrinsic and common, monitored as INR for warfarin) and aPTT (intrinsic, monitored for heparin).
Natural anticoagulants include antithrombin, protein C and S, and tissue factor pathway inhibitor. Direct oral anticoagulants block factor Xa (rivaroxaban, apixaban) or thrombin (dabigatran). Factor V Leiden is a common inherited clotting risk.
Frequently asked questions
What is Hemostasis Cascade?
Intrinsic and extrinsic coagulation pathways converge to convert fibrinogen to fibrin.
Which area of biology covers Hemostasis Cascade, and how advanced is it?
Hemostasis Cascade is one of the 51 topics in Human Physiology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Blood Clotting, Liver Functions, Blood Components.
Why does Hemostasis Cascade matter?
Understanding the cascade lets doctors treat both bleeding and thrombosis.
Can you give an example of Hemostasis Cascade?
Prothrombin time tests the extrinsic pathway.
What should I learn before Hemostasis Cascade?
Work through the Beginner topics in Human Physiology first, such as Homeostasis, Tissues and Organs, Skeletal System, then return to Hemostasis Cascade. Advanced topics assume the Intermediate vocabulary.
What topics are related to Hemostasis Cascade?
The closest topics to Hemostasis Cascade are Blood Clotting, Liver Functions, Blood Components, Renin-Angiotensin-Aldosterone System. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Hemostasis Cascade?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Hemostasis Cascade. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Hemostasis Cascade different from Blood Clotting?
Hemostasis Cascade: Intrinsic and extrinsic coagulation pathways converge to convert fibrinogen to fibrin. Blood Clotting: Platelets and fibrin form a clot to seal damaged vessels. Read both side by side and note what each one explains.
How should I study Hemostasis Cascade step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Blood Clotting and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.