BLOOD CLOTTING–
What is Clotting -
Unless blood is a free-flowing liquid it will not be able to circulate easily throughout the body's blood vessels. However, in being a liquid it could cause a large variety of problems. If there was an injury that broke a large blood vessel it could lead to a large loss of blood. This problem is resolved by the complex mechanism of clotting. The clots form a temporary barrier to prevent blood loss until the vessel walls have healed.
The Clotting Process-
When a blood vessel is injured, platelets begin to collect near the injury, which forms a barrier known as the platelet plug. When the platelets come in contact with an injured area, they swell up, become sticky, and release certain chemicals.
Blood clotting requires many precise reactions to maintain a certain balance between quick and efficient clot formation. This balance has to be kept exact so that your blood will not clot at the wrong time.
Prothrombin and
fribrinogen are two proteins that are produced by the liver that are always present in the plasma of the blood. The injured tissues and platelets release
prothrombin activator and
calcium ions (Ca2+) to change
prothrombin into the enzyme thrombin.
Then the
thrombin splits two short amino acid chains from each fibrinogen molecule.
The ends of the
fibrinogen then join together, forming threads of fibrin. These fibrin surround the platelet plug in the damaged area of the blood vessel and provide the shape for the clot.
Red blood cells are present within the fibrin which makes the clot appear red. After this the clot stops the bleeding, gets smaller, and hardens. Over time the injury is repaired by the growth of new cells which will replace the cells lost because of the injury. When all the healing has finished an enzyme called plasmin in activated and dissolves the fibrin clot.
Clotting:
Some Clotting Problems -
There are many conditions which can cause the clotting process to be disrupted. People who have the
> hereditary disease haemophilia,
> Lack the essential Factor VIII (Antihaemophilic Globulin, or AHG) of blood clotting.
These people can recieve certain injections which will enable ther blood to clot properly.
> If you don't have enough platelets in the blood or lack vitamin K, this will reduce the ability to clot.
(Note: all the above Questions i took from Past ES Papers)