Coagulation of blood

                 COAGULATION OF BLOOD

Coagulation is defined as the process in which blood loses is fluidity and becomes a jelly like mass few minutes after it is shed out or collected in a container.

Factors involved in blood clotting

Factors

1.   Fibrinogen
2. Prothrombin
3. Thromboplastin
4. Calcium
5. Labile factor
6. Accelerin
7. Stable factor
8. Antihemophilic
9. Cristmas
10. Stuart prower
11. Plasma thromboplastin antecedent
12. Hageman
13. Fibrin stabilizing

Mechanism

Enzymes cascade theory

Most of the clotting factors are proteins in the form of enzymes. Normally all the factors are present in the form of inactive proenzyme. These proenzyme must be activated into enzymes to enforce clot formation. It is carried out by a series of proenzyme enzyme conversion reactions. First one of the series is converted into an active enzyme that activates the second one which activates the third one this continues till the final active enzyme thrombin is formed.

Stages of blood clotting

1.   Formation of prothrombin activator

2. Conversion of prothrombin into thrombin

3. Conversion of Fibrinogen into fibrin.

1. STAGE 1:- Formation of prothrombin

Blood clotting commences with the formationof a substance called prothrombin activator which converts prothrombin into thrombin.

Formation of prothrombin activator 2 pathways

1.   Intrinsic pathways

1.During the injury the blood vessel is ruptured endothelium is damaged and collagen beneath the endothelium is exposed.

2.When factor 12 Hagrman comes in contact with the collegen it is converted into activated factor 12 in the presence of kallirein and high molecular weight kinogen.

3.The activated factor 12 converts factor 11 into activated factor 11 in the presence of high molecular weight kinogen.

4.The activated factor 11 activates factor 9 in the presence of factor 4 calcium.

5.Activated factor 9 activates factor 10 in the presence of factor 8 and calcium.

6.When platelet comes in contact with the collagen of damaged blood vessel it gets activated and releases phospholipids.

7.Now the activated factor 10 reaxts with platelet phospholipid and factor 5 to form prothrombin activator.

8.This needs the presence of calcium ions Factor 5 is also activated by positive feedback effect of thrombin

Extrinsic pathway
Pathway

1.Tissues that are damaged during injury releases tissue thromboplastin.

2.Thromboplastin contains proteins phospholipid and glycoprotein which act as proteolytic enzymes.

3.Glycoprotein and phospholipid components of thromboplastin convert factor 10 into activated factor 10 in the presence of factor 7.

STAGE 2:-  CONVERSION OF PROTHROMBIN INTO 

THROMBIN

1.Prothrombin activator that is formed in intrinsic and extrinsic pathway converts prothrombin into thrombin in the 

presence of calcium

2.Once formed thrombin initiates the formation of more thrombin  molecules.

3. The initially formed thrombin activates factor 5. Factor 5 in turn accelerates formation of both extrinsic.

   STAGE 3 :- CONVERSION OF FIBRINOGEN   INTO FIBRIN

1.Trombin converts inactive fibrinogen into Activated Fibrinogen due to loss of 2 pairs of polypeptides from each Fibrinogen molecule.

2.Fibrin monomer polymerizes with other monomer molecules and form loosely arranged strands of fibrin.

stage coagulation

BLOOD CLOT

Blood clot is defined as the mass of coagulation blood which contains RBC WBC and platelets entrapped in fibrin meshwork.

FIBRINOLYSIS

Lysis of blood clot inside the blood vessel is called fibrinolysis. It helps to remove the clot from lumen of the blood vessel. This process requires a substanceccalled plasmin or fibrinolysis.

ANTICOAGULANTS

1.Anticoagulant used to prevent blood clotting inside. The body in vivo.

2.Anticoagulant used to prevent clotting of blood that is collected from thecbody in vitro.

3.Anticoagulant used to prevent blood clotting both in vivo and in vitro.

1. HEPARIN

Heparin is a naturally produced anticoagulant in the body. It is produced bymast cells which are the wandering cells present immediately outside the capillaries in many tissues.

mechanism

Uses of Heparin

Heparin is used as an anticoagulant both in vivo and in vitro.

Clinical use

1.I.V. injection of haparin (0.5 to 1 mg/kg body weight ) postpones clotting for 3 to 4 hours . So it is widely used as an anticoagulant in clinical practice.

2.Heparin is used for many purposes 

3.To prevent intravascular blood clotting during surgery.

 4.While passing the blood through artificially kidney for dialysis. 

5.During cardiac surgery which involves heart lung machine.

6.To preserve the blood before transfusion.

Use in the laboratory

Heparin is also used as anticoagulant in vitro while collecting blood for various investigations. About 0.1 to 0.2 mg is sufficient for 1 ml of blood. It is effective for 8 to 12 hours.

2. COUMARIN

Warfarin and dicoumoral are the derivatives of coumarin

Uses

Dicoumoral and warfarin are the commonly used oral anticoagulants. Warfarin is used to prevent myocardial infarction strokes and thrombosis.

3. EDTA

Ethylenediaminetetraacetic acid is a strong anticoagulant. It is available in 2 forms

Disodium salt (Na2 EDTA

Tripotassium salt ( k3 EDTA)

Mechanism

These substances prevent blood clotting by removing calcium from blood.

Uses

EDTA is used as an anticoagulant both in vivo and in vitro

4. OXALATE COMPOUNDS

Oxalate composed prevent coagulation by forming calcium oxalate which is precipitated later.

Mechanism

Oxalate combines with calcium and forms insoluble calcium oxalate. Thus oxalate removes calcium from blood and lack of calcium prevents coagulation.

Uses

Oxalate compounds are used only as in vitro anticoagulants. 2 mg of mixture is necessary for 1 ml of blood. Since oxalate is poisonous it cannot be used in vivo.

5. CITRATES

Sdium ammonium and patassium citrates are used as anticoagulants.

Uses

It is used to store blood in the blood bank

Citrate is also used in laboratory in the form of formal citrate solution for RBC and platelet counts.

TESTS FOR BLOOD CLOTTING

1. Bleeding time

Bleeding time is the time interval from oozing of blood after a cut or injury till arrest of bleeding. Usually it is determined by Duke method using blotting paper or filter paper method. Its normal duration is 3 to 6 minutes. It is prolonged in purpura.

2. Clotting time

Clotting time is the time interval from oozing of blood after a cut or injury till the formation of clot. It is usually determined by capillary tube method. Its normal duration is 3 to 8 minutes. It is prolonged in hemophilia.

3. Prothrombin time

4. Partial prothrombin time

5. International normalized ratio

6. Thrombin time

BLEEDING DISORDERS

1. Hemophilia

Hemophilia is a group of sex linked inhaerited blood disorders characterized by prolonged clotting time. Usually it affects the males with the females being the carriers.

Symptoms of hemophilia

1. Spontaneous bleeding

2. Prolonged bleeding due to cuts toot Extraction and surgery.

3. Hemorrhage in gastrointestinal and Urinary tract.

4. Bleeding in joints followed by swelling And pain .

5. Appearance of blood in urine.

Causes

Hemophilia occurs due to lack of formation of prothrombin activator.  That is why the coagulation time is prolonged. The formation of prothrombin activator is affected due to the deficiency of factor VIII, IX, XI.

Treatment for hemophilia

Effective therapy for classical hemophilia involves replacement of missing clotting factor.

2. PURPURA

Purpura is a disorder characterized by prolonged bleeding time.

3. TROMBOSIS

Thrombosis or intravascular blood clotting refers to coagulation of blood inside the blood vessels. Normally blood does not clot in the blood vessel because of some factors which are already explained.

Causes

1. Injury to blood vessel

2. Roughened endothelial lining

3. Sluggishness of blood flow

4. Agglutination of RBC

5. Toxic thrombosis

6. Congenital absence of protein C

Complications of Thrombosis

1. Thrombus

2. Embolism and embolus

3. Ischemia

4. Necrosis and infarction

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Milan Tomic

Hi. I’m Designer of Blog Magic. I’m CEO/Founder of ThemeXpose. I’m Creative Art Director, Web Designer, UI/UX Designer, Interaction Designer, Industrial Designer, Web Developer, Business Enthusiast, StartUp Enthusiast, Speaker, Writer and Photographer. Inspired to make things looks better.

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