Question

The mechanical properties of our blood clotting are extremely important to our health. Explain the role of platelets in the blood and the mechanism by which our blood clots. Please be sure to focus any biosignaling that takes place in this process.

Answer 1

Blood clotting or coagulation is the transformation of blood from a liquid into a solid gel. This solid gel is called as a clot. It consists of a network of insoluble protein fibres called fibrin in which the formed elements of blood are trapped.

Blood clotting involves several substances known as clotting factors. These include Calcium ions, many inactive enzymes from liver and various molecules associated with platelets or released by damaged tissues.

In the clotting of blood, there is the conversion of soluble plasma protein fibrinogen to insoluble fibrin. This conversion is catalysed by the enzyme thrombin at the site of the injury, Prothrombinase converts prothrombin into the enzyme thrombin.

There is 2 clotting cascade.

1. Extrinsic pathway: It is a shorter pathway and here a tissue protein called tissue factor or factor III leaks into the blood from cells outside blood vessels. In the presence of calcium, thromboplastin begins a sequence of reactions that ultimately activates clotting factor X.

2. Intrinsic pathway: It is more complex than the extrinsic pathway, it occurs more slowly. Here, activators are either in direct contact with blood or contained within the blood; outside tissue damage is not needed. If endothelial cells become damaged, blood can come in contact with collagen fibres in the connective tissue, around the endothelium of the blood vessel. Contact with collagen fibres activates clotting factor XII, which begins a sequence of reactions that eventually activates clotting factor X.