Question

When you cut your finger or hurt yourself, the wound does not continue to bleed for a long time; usually the blood stops flowing after sometime. why?

Answer 1

Part 1:Coagulation of blood
When there is any injury or trauma, the loss of blood takes place. To prevent the excessive bleeding, a cascade of preventive mechanism called blood coagulation or clotting takes place. This is due to the presence of platelets in our blood.

Part 2: Steps of blood clotting

• Damaged tissues outside blood vessels and the platelets inside the damaged blood vessels secrete a cascade of clotting factors.
• These further activate the prothrombin activator.
• Prothrombin activator catalyzes the conversion of prothrombin into thrombin.
• Thrombin helps in the polymerisation of fibrinogen into long chains called fibrin.
• This mesh of fibrin entraps the blood cells, thus stopping their escape.

All these require the involvement of calcium ions.