10.4 - Mechanism of Blood Clotting

The Necessity for Blood Clotting Mechanism

When you accidentally cut yourself, the blood vessels burst and you start to bleed. After a while, the bleeding will stop by the blood clotting process. Blood clotting is a body mechanism that helps to stop or minimize blood loss from damaged blood vessels. It serves several important functions such as:

• Prevent severe blood loss
• Maintain normal blood pressure
• Maintain circulation of blood
• Prevent entry of microorganisms and foreign substances into the body

Mechanism of Blood Clotting

The blood clotting mechanism involves a series of biochemical reactions in the blood to prevent excessive bleeding after an injury.

Figure 14 - When the blood vessel is damaged, the clumped platelets, damaged cells and clotting factors will form thrombokinase. The thrombokinase will convert prothrombin to thrombin with the help of calcium ions and vitamin K. Thrombin then catalyzes the conversion of soluble fibrinogen to insoluble fibrin. Fibrin forms a mesh of long threads over the wound, trapping red blood cells and sealing the wound. The resulting blood clot hardens when exposed to air to form a scab.

Health Issues Related to Blood Clotting

A defect at any step in the blood clotting process can result in impaired blood clotting. Problems related to impaired blood clotting include hemophilia, thrombosis and embolism.

• Hemophilia

  • Hereditary disease where the blood does not clot normally.
  • Lack of the gene for production of certain clotting factors
  • Can die from excessive bleeding, even from minor cuts
  • Can also experience spontaneous internal bleeding, even though no injury happens.

• Thrombosis

  • Refers to a clot formation inside an unbroken blood vessel.
  • The clot is called a thrombus.
  • Thrombosis can be caused by defect in the blood vessel walls or the blood flows too slowly.

• Embolus

  • Sometimes, a thrombus can dislodge and move in the bloodstream.
  • A moving blood clot is a bloodstream is known as an embolus.
  • The embolus can block the flow of blood in narrow arteries.