In the region of injury or leakage from a blood vessel,blood oozes out
.#the platelets rupture & release a substance called thromboplastin.
# in the presence of calcium, thromboplastin acts on plasma protein prothrombin & forms a proteolytic enzyme called thrombin .
# vitamin k is essential for the formation of prothrombin in liver. thrombin acts on a soluble plasma protein fibronogen & changes into insoluble fibrin.
# fibrin undergoes rapid polymerisation to form long fibres. the fibres form a network over the damaged wall of blood vessel & exposed part of the skin.
# it entraps blood corpuscles & forms a jelly like mass called blood clot.
# the clot contracts & solidifies . a liquid called serum is expelled.