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Related Concept Videos

Extrinsic and Intrinsic Pathways of Hemostasis01:20

Extrinsic and Intrinsic Pathways of Hemostasis

Blood clotting or coagulation involves extrinsic and intrinsic pathways, which ultimately merge into the common pathway, forming a fibrin clot.
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which forms a...
Coagulation01:09

Coagulation

The coagulation phase is a critical part of the body's process to prevent blood loss following injury to blood vessels. It involves chemical reactions that form a clot to seal the injured area. The clotting process begins shortly after injury, within 15-20 seconds for severe damage and 1-2 minutes for minor injuries.
During the coagulation phase, clotting factors, or procoagulants, play a vital role in initiating and progressing the coagulation cascade. This cascade is a series of reactions...
Coagulation01:06

Coagulation

Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...
Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants01:18

Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants

Oral anticoagulants are vital tools in preventing and treating blood clotting disorders. This diverse class of medications can be categorized as vitamin K antagonists, exemplified by warfarin, and direct thrombin inhibitors (DTIs), such as dabigatran, as well as factor Xa inhibitors, including rivaroxaban.
Warfarin, a prominent vitamin K antagonist family member, exerts its effect by inhibiting the enzyme VKORC1 (vitamin K epoxide reductase complex 1). By hindering this enzyme, warfarin...
Anticoagulant Drugs: Low-Molecular-Weight Heparins01:30

Anticoagulant Drugs: Low-Molecular-Weight Heparins

Hemostasis is a crucial process that prevents excessive blood loss from damaged blood vessels. It involves various mechanisms such as vasoconstriction, platelet adhesion and activation, and fibrin formation. The importance of each mechanism depends on the type of vessel injury. In contrast, thrombosis is the abnormal formation of a blood clot within the blood vessels, leading to potential complications if the clot obstructs blood flow. Thrombosis can be caused by increased coagulability of the...
Clot Retraction and Fibrinolysis01:16

Clot Retraction and Fibrinolysis

After a fibrin clot is formed, the next step is clot retraction, a vital process facilitated by platelet contractile proteins, such as actin and myosin. These proteins pull the fibrin strands closer together and condense the clot. This action reduces the size of the clot, creating a smaller, denser structure that effectively seals off the damaged vessel. Clot retraction consolidates the clot and helps with wound healing by bringing the edges of the damaged blood vessel closer together.

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Related Experiment Video

Updated: Jun 13, 2026

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
13:08

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

Published on: September 9, 2012

Coagulation procofactor activation by factor XIa.

M F Whelihan1, T Orfeo, M T Gissel

  • 1Department of Biochemistry, University of Vermont College of Medicine, Burlington, VT, USA.

Journal of Thrombosis and Haemostasis : JTH
|May 12, 2010
PubMed
Summary
This summary is machine-generated.

Factor XIa (FXIa) activates both Factor V (FV) and Factor VIII (FVIII) at plasma concentrations. This finding is critical for understanding the activated partial thromboplastin time (APTT) assay performance in diagnosing hemophilia.

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Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation
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A Microfluidic Flow Chamber Model for Platelet Transfusion and Hemostasis Measures Platelet Deposition and Fibrin Formation in Real-time
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A Microfluidic Flow Chamber Model for Platelet Transfusion and Hemostasis Measures Platelet Deposition and Fibrin Formation in Real-time

Published on: February 14, 2017

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Last Updated: Jun 13, 2026

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay
13:08

Measurement of Factor V Activity in Human Plasma Using a Microplate Coagulation Assay

Published on: September 9, 2012

Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation
04:37

Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation

Published on: May 23, 2025

A Microfluidic Flow Chamber Model for Platelet Transfusion and Hemostasis Measures Platelet Deposition and Fibrin Formation in Real-time
09:38

A Microfluidic Flow Chamber Model for Platelet Transfusion and Hemostasis Measures Platelet Deposition and Fibrin Formation in Real-time

Published on: February 14, 2017

Area of Science:

  • Hemostasis and Thrombosis Research
  • Biochemistry of Blood Coagulation
  • Clinical Diagnostics

Background:

  • The extrinsic pathway relies on thrombin to activate Factors V and VIII.
  • In the activated partial thromboplastin time (APTT) assay, the activators of procofactors remain unidentified.
  • Factor XIIa initiates a cascade activating Factor XI, which then activates Factor IX in the presence of calcium.

Purpose of the Study:

  • To investigate the hypothesis that Factor XIa (FXIa) can activate Factor VIII (FVIII) and Factor V (FV).

Main Methods:

  • Recombinant FVIII and plasma FV were incubated with FXIa.
  • Procofactor activity and integrity were assessed using commercial clotting assays.
  • Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) was employed to analyze protein integrity.

Main Results:

  • Kinetic analyses demonstrated FXIa-catalyzed activation and inactivation of FV and FVIII.
  • The timing and specific cleavage sites for FXIa on FV and FVIII were determined.
  • FXIa was shown to activate both FV and FVIII at physiologically relevant plasma protein concentrations.

Conclusions:

  • FXIa activates both FV and FVIII at plasma protein concentrations.
  • Computational modeling indicates that FXIa-mediated procofactor activation during APTT assay preincubation is crucial for assay performance.
  • These findings may have significant clinical implications for diagnosing and managing hemophilias and FVIII inhibitors.