Coagulation Mechanism

DIGITAL ASSINGMENT – 2 (ENVIRONMENTAL ENGINEERING)
PRABHAT KUMAR (15BCL0032) (SLOT – A1)
The coagulation mechanism
The blood clothing system or coagulation pathway, like the complement system, is a proteolytic cascade. Each enzyme of the pathway is present in the plasma as a zymogen, in other words in an inactive form, which on activation undergoes proteolytic cleavage to release the active factor from the precursor molecule. The coagulation pathway functions as a series of positive and negative feedback loops which control the activation process. The ultimate goal of the pathway is to produce thrombin, which can then convert soluble fibrinogen into fibrin, which forms a clot. The generation of thrombin can be divided into three phases, the

Contact activation of the coagulation pathway, in addition to promoting blood clotting, results in the generation of plasminogen activator activity, which is involved in fibrinolysis or clot removal. Activated Hageman factor and its peptides can also initiate the formation of kallikrein from plasma prekallikrein, and this triggers the release of bradykinin from kininogens in the plasma. Kinins are responsible for dilating small blood vessels, inducing a fall in blood pressure, triggering smooth muscle contraction, and increasing the permeability of vessel walls. In addition, activation of the coagulation pathway produces a vascular permeability factor, as well as chemotactic peptides for professional

Coagulation due to Brownian motion is an important particle growth mechanism in situations where small particles are at a high concentration or where the long-term behavior of suspended particles is of interest. The coagulation kernel and corresponding theories are well established for the free-molecule regime and the near-continuum plus continuum regimes. For several decades, many researchers have studied coagulation enhancement. Van der Waals forces which result from the interaction of fluctuating dipoles are known to have an influence on particle coagulation and to increase the rate of aerosol coagulation. Due to their important role, the researchers added van der Waals forces to the present model as an enhancement factor to the Brownian coagulation kernel. To account for the effect of interparticle forces in the transition regime, the coagulation rate constant is given by Sceats, (1989) as