MICROANATOMY

Detailed explanation-1: -Fibrin is the insoluble fibrous protein formed from fibrinogen, a soluble protein. Fibrin forms a mesh-like or jelly-like substance at the injury site and ultimately, the blood clot is formed when the red blood cells get entangled with the mesh-like substance.

Detailed explanation-2: -Fibrinogen is a soluble macromolecule, but forms an insoluble clot or gel on conversion to fibrin by the action of the serine protease thrombin, which is activated by a cascade of enzymatic reactions triggered by vessel wall injury, activated blood cells, or a foreign surface (Fig. 13.1).

Detailed explanation-3: -Fibrin is produced upon cleavage of the fibrinopeptides by thrombin, which can then form double-stranded half staggered oligomers that lengthen into protofibrils. The protofibrils then aggregate and branch, yielding a three-dimensional clot network.

Detailed explanation-4: -Fibrin is essential for clot contraction because it propagates the platelet-generated contractile forces through the entire network that comprises a clot or thrombus. The structure and rheological properties of fibrin gels are important because they determine the degree of platelet-mediated contraction.