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Blood Coagulation

Last Updated : 14 Nov, 2022
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Body fluids are substances that are created by the body and then either circulated within it or excreted from it. Examples of these substances include blood, lymph, milk, and saliva.

The two most crucial bodily fluids in the human body are blood and lymph. Plasma, white blood cells, red blood cells, and platelets all make up blood. Inside the lymphatic veins, a colorless fluid called lymph circulates.

Blood Coagulation/ Clotting

The most prevalent fluid in our bodies is blood, which circulates under intense pressure throughout the body and keeps it working. Significant blood loss can occasionally result in death.

Blood coagulation is the process of creating a clot or thrombus to stop the body from losing too much blood. It is a mass that resembles gel that is created in the blood by platelets and fibrin.

Fibrin, platelets, and blood cells make up a blood clot. Thrombin is an enzyme that promotes the development of a stable blood clot. The polymerization of insoluble fibrin from fibrinogen is catalyzed by the thrombin enzyme. Prothrombin is used to make thrombin. The prothrombin activator performs the conversion of prothrombin to thrombin. Both the intrinsic and extrinsic blood clotting pathways can activate prothrombin activator. When a blood vessel is injured, intrinsic and extrinsic blood clotting pathways start and move forward to activate the prothrombin activator pathways. 

While the intrinsic process is slower but more focused, the extrinsic pathway is faster. Maintaining adequate blood clotting activity necessitates both pathways.

Coagulation of Blood


Intrinsic Pathway

A mechanism known as intrinsic blood clotting takes place automatically in the body to stop bleeding. Contact with tissue factor, a protein present on cell surfaces, causes it to start. Blood and tissue factors interact, starting a chain of events that eventually results in the formation of a clot.

Most bleeding episodes are stopped by the intrinsic route, which is the body’s main clotting mechanism. However, occasionally the intrinsic mechanism is insufficient to stop bleeding. This can happen if there is significant tissue damage or if the patient has a medical condition that affects their ability to produce clots. In these situations, it could be necessary to open the extrinsic pathway in order to establish hemostasis.

Extrinsic Pathway

The body must create a clot when a blood vessel is damaged in order to limit excessive bleeding. Blood clotting is a complicated process that involves numerous unique proteins and cells. Extrinsic and intrinsic are the two primary processes that result in clot formation.

When a tissue factor, a protein present on the surface of cells, comes into contact with blood, the extrinsic route is activated. Though less accurate, this approach is typically faster than the intrinsic pathway. As a result, the extrinsic pathway has a higher likelihood of causing undesired clotting (such as in the case of a heart attack).

When tissue factors are not present, the intrinsic route is activated. Instead, contact with other proteins or harmed cells activates a protein by the name of Factor XII. Despite being slower than the extrinsic approach, this pathway is more accurate. The intrinsic pathway hence has a lower propensity to result in unintended clotting.


  • Extrinsic and intrinsic are the two main routes by which blood clots. When blood contacts damage the vessel wall, the extrinsic channel is opened up.
  • When blood interacts with an alien substance like a virus or bacteria, the intrinsic route is set off. The production of a fibrin clot is the end result of both paths. But there are also significant variations between the two routes.
  • Faster than the intrinsic pathway is the extrinsic pathway. This is so because the extrinsic pathway uses already-formed components that are found in the blood. The intrinsic process, in contrast, necessitates the creation of fresh clotting components. As a result, the intrinsic pathway produces clots more slowly.
  • Larger wound closure is also more successful using the extrinsic pathway. This is so that the extrinsic process, as opposed to the intrinsic pathway, creates a stronger clot. However, because the intrinsic pathway results in a more confined clot, it is more efficient at closing off tiny wounds.
  • Both pathways are crucial for blood clotting in the end. The size and location of the incision determine which pathway. 

Treatment Implications

Treatment options may be affected by the distinction between intrinsic and extrinsic clotting pathways. For instance, medications that target factor VIIa, a protein involved in the extrinsic route, are used to treat hemophilia A and B. Von Willebrand disease is treated with factor VIII inhibitors, a protein involved in the extrinsic route.

For abnormalities of the intrinsic route, there is no specific treatment available at the moment. The intrinsic pathway is less well understood, but there may be potential to create new medications that target this pathway directly.

Process of Blood Coagulation

The mechanism by using which the body stops bleeding to forestall regular loss of blood is recognized as hemostasis. The entire process is divided here into three predominant steps:

  • The primary hemostasis involves the vasoconstriction technique, which reacts to the body’s injury to the vascular wall. 
  • The vascular partitions respond quickly to an injury by reducing the amount of blood flow in the contaminated area.
  • The platelets also perform a crucial role in covering the wounded area and stopping the bleeding. They also stimulate a process known as secondary hemostasis, which produces a fibrin clot. 
  • As a result, serotonin, ADP, and thromboxane that have been stored in granular components are released, activating platelets in the blood plasma as well.
  • A blood clot must inevitably form since the platelets by themselves can no longer tightly shut the damages caused to the artery walls. 
  • Numerous clotting factors that activate one another in the clotting cascade are necessary for the development of blood clots.
  • A soluble plasma protein called fibrinogen is created as a result of this cascade. The fibrinogen is converted into fibrin proteins, which eventually bind to form a clot. 
  • White platelet clots are known as a thrombus, and a red thrombus, which also includes purple blood cells, is recognized.

Deep Vein Thrombosis

A dangerous condition known as deep vein thrombosis occurs when a blood clot forms in one or more of our body’s deep veins. Most of the time, the blood clot in the vein may dissolve, travel through the body, affect several organs, including the lungs and chest, and obstruct the flow of blood.

The most typical DVT symptoms include muscle pain, particularly in the legs, and swelling, however in most cases, these clots can develop without any obvious symptoms. They frequently occur for scientific reasons or as a result of the body’s movements occurring less frequently.

Need for Blood Coagulation

Coagulation, or blood clotting, is a crucial mechanism that stops excessive bleeding after a blood artery is injured. A clot is formed over the wound by platelets, a kind of blood cell, and proteins in plasma, the liquid component of blood, which work together to halt the bleeding. Following the healing of the wound, your body will often spontaneously dissolve the blood clot.

Hemostasis, the halting of blood loss from a damaged vessel, may ensue, followed by repair. Platelet activation, adhesion, and aggregation as well as fibrin deposition and maturation are all components of the coagulation mechanism. Almost immediately after damage to the endothelium lining a blood artery, coagulation starts. 

FAQs on Blood Coagulation 

Question 1: What is a coagulation test?


Coagulation assays assess the speed and consistency of blood clotting. Your doctor can use testing to determine your risk of excessive bleeding or the occurrence of clots (thrombosis) in one of your blood arteries.

Question 2: What distinguishes hemostasis from coagulation?


Blood coagulation and hemostasis, a tightly controlled process, are cell-based biochemical processes intended to stop blood loss after vascular injury and to supply the essential cellular and protein components for vascular growth and repair.

Question 3: What kinds of thrombus are there?


There are two different forms of thrombus: red and white. White thrombus, which is platelet clots, and red thrombus, which are red blood cells, respectively, are terms used to describe blood clots.

Question 4: What distinguishes extrinsic from intrinsic pathways?


There are two distinct blood coagulation pathways: intrinsic and extrinsic. When a blood vessel is damaged, the extrinsic pathway is activated, but the intrinsic pathway is activated when the endothelium, the layer of cells that lines the blood vessels, is harmed.

Question 5: Describe DVT.


A blood clot that forms in one or more of our body’s deep veins is known as deep vein thrombosis, a dangerous disorder. By obstructing blood flow, it has an impact on crucial organs like the brain, lungs, and kidneys.

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