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Coagulation

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...

Coagulation

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...

Extrinsic and Intrinsic Pathways of Hemostasis

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...

Introduction to Hemostasis

Introduction to Hemostasis

Hemostasis is a complex physiological process that prevents excessive bleeding when a blood vessel is injured. It's crucial for maintaining the integrity of the circulatory system, as it ensures that our blood remains fluid while still within the vascular network and yet clots to prevent blood loss upon vessel injury.
The three phases of hemostasis involve many clotting factors present in plasma and several substances released by platelets and injured tissue cells. It is a fast, localized, and...

Formation of the Platelet Plug

Formation of the Platelet Plug

The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...

Clot Retraction and Fibrinolysis

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: Jul 2, 2026

Mechanical Vessel Injury in Zebrafish Embryos

Mechanical Vessel Injury in Zebrafish Embryos

Published on: February 17, 2015

Urochordate histoincompatible interactions activate vertebrate-like coagulation system components.

Matan Oren¹, Marie-line Escande, Guy Paz

¹Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel. matan@ocean.org.il

|September 5, 2008

Summary

The colonial ascidian Botryllus schlosseri utilizes a vertebrate-like coagulation system for its immune rejection response. This study reveals key clotting factors involved in the rejection of histoincompatible colonies.

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Assessment of the Anticoagulant and Anti-inflammatory Properties of Endothelial Cells Using 3D Cell Culture and Non-anticoagulated Whole Blood

Assessment of the Anticoagulant and Anti-inflammatory Properties of Endothelial Cells Using 3D Cell Culture and Non-anticoagulated Whole Blood

Published on: September 5, 2017

Area of Science:

Marine biology
Immunology
Evolutionary biology

Background:

The colonial ascidian Botryllus schlosseri exhibits an allorecognition system leading to inflammatory rejection of histoincompatible colonies.
A significant number of vertebrate coagulation genes were identified in Botryllus during allorejection, suggesting a potential role for clotting in innate immunity.

Purpose of the Study:

To investigate the involvement of a vertebrate-like clotting system in the innate immunity and allorejection processes of Botryllus schlosseri.
To characterize the molecular and physiological aspects of clot formation during histoincompatible reactions.

Main Methods:

Analysis of differentially expressed sequence tags (ESTs) to identify coagulation-related genes.
Monitoring of clot types (points of rejection; POR) and their morphology.
Gene expression analysis (in situ hybridization, immunohistochemistry) of coagulation orthologues.
Assessment of anti-coagulant effects (heparin) on rejection and heartbeats.

Main Results:

Nine coagulation orthologue transcripts were specifically expressed during Botryllus rejection.
Heparin significantly affected POR formation and heartbeats, indicating anticoagulant involvement.
Fibrinogen and von Willebrand factor orthologues showed specific and common expression patterns.
Immunohistochemistry detected fibrinogen in specific Botryllus compartment cells.

Conclusions:

Molecular, physiological, and morphological data strongly suggest the involvement of vertebrate-like coagulation elements in urochordate immunity.
This coagulation system in Botryllus functions in immune defense rather than in response to vascular injury.