What is blood clotting?
Blood Clotting Process is a haemostatic mechanism. Normally on getting hurt or getting a cut blood starts flowing. The mechanism by which the body stops this flow of blood is known as clotting or coagulation of blood. So blood coagulation or clotting is the ability of the body to prevent blood loss from a cut or injured part of the body. It is a topic related to biology class 12.
How does the process of blood clotting occur?
These are the four substances that are required for the clotting of blood -
1.Prothrombin
2.Fibrinogen
3.Calcium
4.Thromboplastin
Prothrombin,fibrinogen and calcium are found in the circulating blood.Thromboplastin ( a lipid or a compound like that of fat consisting of phosphorus )is either absent or found in very small amount in blood plasma. It is released either from the damaged platelets or when a tissue cell or blood vessel gets damaged. So prothrombin is released from two types of sources i.e intrinsic and extrinsic. After the release of prothrombin a number of events take place to produce a jelly like substance known as clot. Prothrombin is converted into its active form called thrombin by thromboplastin in the presence of calcium ions. Thrombin works like an enzyme and changes the soluble
fibrinogen into insoluble fibres. Fibrin deposits as fine threads forming a frame-work of the clot.
Due to the lack of sufficient prothrombin, blood doesn't clot in the blood vessels. Heparin present in the blood also prevents the coagulation or clotting of blood.
The process of Co-agulation involves different catalytic events that act like an enzyme cascade in which each product of the reaction plays an important role in activating the next reaction. There are 13 types of plasma factors that are recognized by the International Commission on Blood Co-agulation. The process of co-agulation is delayed if even one factor is missing in a person. The process of blood clotting normally takes about 2-8 minutes after an injury.
What are blood co-agulation factors?
The blood co-agulation factors are -
1.Prothrombin
2.Fibrinogen
3.Thromboplastin tissue factor
4.Calcium
5.Accelerator globin or Labile factor (ACG)
6.Now considered identical to factor V
7.Stable factor (SPCA) or Proconvertin
8.Antihaemophilic factor (AHF) Haemophilia-A is caused due to it's deficiency
9.Christmas factor or Plasma thromboplastin component (PTC) . Haemophilia-B or christmas disease is caused due to its deficiency.
10.Sturat Prower Factor
11.Plasma thromboplastin antecedent (PTA). Haemophilia-C is caused due to its deficiency.
12.Hageman or surface factor
13.Fibrin-stabilizing factor or Laki Lovand factor
What is the role of vitamin K in blood co-agulation?
Vitamin K is vey important for the clotting of blood. It plays an important role in the production of prothrombin in the liver. So it is also known as antihaemorrhagic vitamin. Deficiency or lack of absorption of vitamin K disturbs the process of blood clotting.Green leafy vegetables are a good source of vitamin K. Colon bacteria also synthesizes vitamin K.
What are anticoagulants?
Anticoagulants are those substances that check the clotting of blood. These are -
1.Heparin - It is a natural anticoagulant found in the blood plasma and is formed in the liver. It stops the process of changing of prothrombin into thrombin. So it is known as antiprothrombin.
2.Hirudin - Hirudin is a type of anticoagulant found in the saliva of leech. It helps to prevent the clotting of victim's blood.
3.Warfarin - Warfarin is an anticoagulant that is of plant origin. It lowers the activity of vitamin K that lowers the formation of prothrombin and some of the plasma co-agulating factors such as 7 and 9 from the liver cells.
4.Sodium oxalate, sodium citrate and ethylene diamine tetra acteic acid (EDTA) - These substances are used in blood banks in anti coagulants. They prevent co-agulation of blood by precipitating Ca++ from blood. Sodium citrate is used as an anticoagulant in the blood that is to be used in transfusion because sodium citrate can be mobilized in the body easily.
What is thrombosis?
When a blood clot is formed in an intact blood vessel, it is known as thrombosis and the internal clot is known as thrombus. It blocks the flow of blood in the blood vessels and is dangerous if occurs in the vessels of brain or heart.
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