Clotting of Blood: When you get a cut, does it bleed continuously? No, right? Then what happens that stops the bleeding? Clotting of blood takes place to stop your bleeding. Clotting of blood is an important process that prevents excessive bleeding when a blood vessel is injured. Coagulation is a dynamic process, and understanding the blood coagulation system has evolved over the recent years in anaesthetic practice. ‌

This‌ ‌article covers‌ ‌the‌ importance of clotting of blood, clotting factors, disorders related to blood clotting, ‌and‌ ‌much‌ ‌more.‌ ‌Scroll down to discover ‌more‌ ‌interesting‌ ‌facts‌ ‌about‌ ‌the‌ clotting of blood.

What is the Clotting of Blood?

Blood clotting or clotting of blood, which also refers to the process called haemostasis, is the formation of a gel-like or clot-like structure, preventing bleeding or loss of blood, i.e., haemorrhage in cases of injured blood vessels.

Fig: A Picture Showing Clotting of Blood Cells

It also takes place in a blood sample that is drawn from a body and kept in a plain test tube or a vial. The straw-coloured liquid, called serum, refers to the plasma minus blood coagulation factors.

The gel or a clot consists of a network of insoluble protein fibres called fibrin, in which the formed elements of blood get entrapped. Blood clotting, coagulation, or the process of gel formation consists of a series of chemical reactions to result in the formation of a fibrin network.

Clotting of Blood Factors

Blood Clotting factors are proteins in the blood that help control bleeding. Coagulation factors are proteins in the blood that help control bleeding. There are several different coagulation factors in our blood. When there is a cut or other injury that causes bleeding, our coagulation factors work together to form a blood clot.

1. The majority of clotting factors are precursors of proteolytic enzymes known as zymogens that circulate in an inactive form. The activation of each zymogen is depicted by suffixing the letter “a” to the Roman numeral identifying that particular zymogen.
2. A recent theory of blood clotting is the cascade theory proposed by Macfarlane. According to this theory, 13 factors are required for blood clotting. VI factor is hypothetical. Actually, there is no factor VI.

Clotting Factor	Synonym	Characteristic
Factor I	Fibrinogen	1. This glycoprotein is synthesized in the liver. 2. It contains 3 pairs of non-identical polypeptide chains and soluble in plasma.
Factor II	Prothrombin	1. This glycoprotein is synthesized in the liver.
Factor III	Thromboplastin or tissue factor	1. Lipoprotein is secreted in an inactive form known as prothromboplastin which gets activated by proconvertin of plasma tissues.
Factor IV	Calcium ions	1. Required for the formation of intrinsic and extrinsic thromboplastin and for the conversion of prothrombin to thrombin
Factor V	Proaccelerin or labile factor	1. This glycoprotein is synthesized in the liver. 2. It is absent in serum.
Factor VI	Accelerin	1. Hypothetical activation product of proaccelerin
Factor VII	Serum Prothrombin Accelerator	1. Synthesized in the liver. 2. Associated with prothrombin and accelerates tissue thromboplastin formation from damaged tissues
Factor VIII	Anti-haemophilic factor or platelet cofactor	1. This glycoprotein is synthesized in the liver. 2. This is required for prothrombin activator formation from blood constituents. Its deficiency causes haemophilia-A.
Factor IX	Anti-prothrombin II or platelet cofactor II or Plasma Thromboplastin Component (PTC)	1. This glycoprotein is synthesized in the liver. 2. Its deficiency causes haemophilia-B.
Factor X	Stuart factor	1. This glycoprotein is synthesized in the liver. 2. Its deficiency causes nose bleeding (epistaxis)
Factor XI	Plasma Thromboplastin Antecedent (PTA)	1. This glycoprotein is required for stage 1 of the intrinsic pathway. 2. It is synthesised in the liver. Its deficiency causes haemophilia-C.
Factor XII	Hageman factor or surface factor	1. This glycoprotein is present in both plasma and serum. 2. It is required for the formation of the prothrombin activator complex. 3. Its deficiency results in delayed blood clotting
Factor XIII	Fibrin stabilizing factor	1. This Glycoprotein causes polymerization of soluble fibrinogen to insoluble fibrin. 2. Its deficiency causes a hemorrhagic state

Table: Clotting Factors in the Blood and their Synonyms with Characteristics

Mechanism of Clotting of Blood

The process of Blood Clotting can be described under three major steps, which are given below:

First step: At the site of an injury or cut or any wound, the blood platelets disintegrate and release a phospholipid, called platelet factor III (Platelet thromboplastin). Injured tissues also release a lipoprotein factor called thromboplastin. These two factors combine with calcium ions \(\left( {{{\rm{C}}^{ + + }}} \right)\) and certain proteins of the blood plasma to form an enzyme called prothrombinase.
Second step: The prothrombinase inactivates heparin or anti-prothrombin-anticoagulant in the presence of calcium. Prothrombinase catalyzes the breakdown of prothrombin (inactive plasma protein) into an active protein called thrombin and some small peptide fragments.
Third step: Thrombin acts as an enzyme and first brings about depolymerization of fibrinogen (a soluble plasma protein) into its monomers. Later, thrombin stimulates repolymerization of these monomers into long insoluble fibre-like polymers called fibrin. The thin, long solid fibres of fibrin form a dense network upon the wound or the injury and trap blood corpuscles (RBCs, WBCs, and platelets) to form a clot. The clot seals the wound and stops bleeding. Soon after, the clot starts contracting, and a pale-yellow fluid called serum starts oozing out. This serum is blood plasma minus fibrinogen and blood corpuscles.

Fig: A Image Showing the Process of Blood Clotting

The Mechanism of Clotting of Blood is given below through a flow chart.

Fig: A flow chart showing the mechanism of clotting of Blood

Why Does Blood not Clot within the Blood Vessels?

The blood contains an anticoagulant called heparin (antithrombin) that does not allow the formation of prothrombinase within the blood vessels.

In certain diseases, blood clots are formed within the blood vessels. These clots are called thrombi, and their formation is called thrombosis. Thrombosis in the coronary artery leads to a heart attack. When a thrombus is transported by the bloodstream it is called embolus which causes embolism when lodged in a vessel and cuts off circulation.

Types of Blood Clots

Our human circulatory system is made up of vessels called veins and arteries, which transport blood throughout our body. Blood clots can form in veins or in arteries.

1. When a blood clot occurs in an artery, then it is known as an arterial clot. This type of clot in individuals causes symptoms immediately and requires emergency treatment. The symptoms of an arterial clot include severe pain and also can paralyse those parts of the body. This can lead to a heart attack or even stroke.
2. A blood clot that occurs in a vein is known as a venous clot. These types of clots may build up more slowly over time, but they can still be life-threatening for an individual. The most serious type of venous clot is known as deep vein thrombosis.

Deep Vein Thrombosis (DVT) – Clotting of Blood Symptoms

An unexpected clot in our body can lead to very serious problems and may even cause death. In an artery, it can give an individual a heart attack or a stroke. If it happens in a vein, an individual can feel pain and swelling. A clot deep inside our body is called a deep vein thrombosis (DVT).  A blood clot is a clump of blood that’s turned into a solid-state.

Fig: An image showing deep vain thrombosis in the leg.

1. Deep vein blood clots typically form in our thigh or in our lower legs, but they can also develop in other areas of our body.
2. Other names associated with this condition may include thromboembolism, post-phlebitic syndrome and post-thrombotic syndrome.

As per the CDC (Centers for Disease Control and Prevention), the symptoms of this DVT usually occur in about half of the people who have the CDC condition. The common symptoms are given below:
1. There is swelling in the foot, ankle, or leg, usually on one side of the body.
2. Cramping pain in the affected leg usually begins in the calf.
3. Severe pain in the foot and ankle.
4. The affected skin turns to a pale or reddish or bluish colour.

People with an upper extremity DVT, or a blood clot in the arm, may also not experience any symptoms. If they do, common symptoms are as follows:
1. Severe neck pain and shoulder pain.
2. Swelling in the arm or hand with bluish skin colour.
3. The pain leads to weakness in the hand.

People may not understand that they have this deep vein thrombosis unless they have gone through emergency treatment for a pulmonary embolism, i.e., a blood clot in the lung.
A pulmonary embolism may happen when a DVT clot has moved from the arm or leg into the lung. It is life-threatening when an artery in the lung becomes blocked.

Fig: An Image Showing the Pulmonary Embolism

Treatment for DVT

Some of the treatment includes:
1. By preventing the clot from getting bigger.
2. By preventing the clot from breaking loose that may travel to the lungs.
3. Use of blood thinners – these are anticoagulants that can prevent clots from getting bigger and reduces the risk of getting more clots in the body.
4. The most commonly used injectable blood thinners for DVT are fondaparinux (Arixtra) and enoxaparin (Lovenox).

Clotting of Blood Disorders

Haemophilia

Haemophilia is a rare disorder in which an individual’s blood doesn’t clot normally because it lacks sufficient blood-clotting proteins called clotting factors.Haemophilia A is the most common form of haemophilia which is associated with the deficiency of factor VIII. Haemophilia is a hereditary disorder and is an “X- linked recessive” disorder that occurs in males. The severity of the bleeding tendency is directly related to the levels of the coagulation factors.
1. It is transmitted through females to males who are sufferers.
2. Females who carry a single mutated gene are generally asymptomatic and not affected.
3. People who have Haemophilia often have longer bleeding after some sort of contact to injury. 
4. People who have severe Haemophilia start to have spontaneous bleeding in the joints and muscles all around their bodies.

Symptoms of Haemophilia

The symptom of Haemophilia is shown below through a pictorial representation.

Fig: An image showing the symptoms of Haemophilia.

Blood Clot in the Heart / Heart Attack

A blood clot in the heart causes a heart attack. The heart is a less common location for a blood clot, but it can still happen. A blood clot in the heart could cause our chest to hurt or feel heavy. Light-headedness and shortness of breath are other potential symptoms.

Blood Clot in the Brain / Stroke / Cerebral Thrombosis

A blood clot in the brain is also known as a stroke. A blood clot in our brain could cause a sudden and severe headache, along with some other symptoms, including sudden difficulty speaking or seeing, confusion, seizures, speech problems, and weakness, sometimes on just one side of the body.

Clotting of Blood Treatment

Role of Vitamin K in Clotting of Blood

Vitamin K is essential for blood clotting as it is necessary for the synthesis of prothrombin in the liver.
1. Warfarin is a vitamin K antagonist and hence inhibits the synthesis of four blood coagulation factors.
2. Anticoagulants: These are those agents that prevent blood coagulation and includes:
3. Oxalates and citrates of sodium and potassium replace calcium ions in the plasma.
4. Use of EDTA (Ethylene diamine tetraacetic acid) and CPD (Citrate phosphate dextrose) that acts as a calcium chelating agent.
5. Magnesium sulphate adsorbs fibrin.
6. Heparin is the one that prevents conversions of prothrombin to thrombin by activating antithrombin III.

Summary

Clotting of Blood is a severe problem and may even cause the death of an individual. Visit your doctor or go to the emergency room right away when you face these problems. A clot can be deadly, and you won’t know for sure you have it until you get it checked. Through this article, we got to know about blood clotting and its disorders. Hence, we should not neglect anything related to health.

Frequently Asked Questions (FAQs) on Blood Clots

Q.1. Which vitamin helps in the clotting of blood?
Ans: Vitamin K is a group of vitamins that helps in clotting blood.

Q.2. What is the clotting of blood?
Ans: When an injury is caused to a blood vessel, bleeding starts which is stopped by a process called blood coagulation or blood clotting. 

Q.3. What is the mechanism of blood clotting? 
Ans: The mechanism of blood clotting is given below:

Q.4. What is the role of vitamin k in blood clotting?
Ans: Vitamin K is essential for blood clotting as it is necessary for the synthesis of prothrombin in the liver.

Q.5. What prevents the clotting of blood?
Ans: The clotting of blood can be prevented by using anticoagulants.

Q.6. What is the full form of DVT?
Ans: The full form of DVT is Deep vein thrombosis.

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