When you experience a wound, what prevents your body from draining the blood that circulates within your body?
A technical description for this process is when blood platelets work together to form a thrombus in a coagulation cascade. The lay term is the formation of a blood clot.
For example, when you are cutting vegetables for an evening meal and you slip and cut your skin the nerve impulses race to the brain at 250 miles an hour. Your brain recognizes the injury site and platelets begin to converge at the point of the wound.
Interestingly once a platelet has attached to the wounded area it releases a chemical that alerts other platelets to come and help stop the flow of blood. Once enough platelets have converged on the area a coagulation cascade is developed. According to the University of Illinois at Urbana-Champaign College of Medicine, “The goal of the cascade is to form fibrin, which will form a mesh within the platelet aggregate to stabilize the clot. All of the factors have an inactive and an active form. Once activated, the factor will serve to activate the next factor in the sequence until fibrin is formed. ” 
Wikipedia describes fibrin as, “[A] protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a “mesh" that forms a hemostatic plug or clot (in conjunction with platelets) over a wound site. ” 
Essentially when our bodies experience a wound, a rescue team is dispatched to stop the flow, provide a sophisticated covering and speed the process of healing.
The presence of platelets within the human body is a wonderful mechanism for preserving life in the event of lacerations.
The above description of how this system works is stripped down to make it easier to understand. The fact is the blood clotting system within the human body is incredibly complex. Without the proper components in just the right amounts, activated at just the right time blood clotting would not work and the organism would not survive.
The blood clotting system is what is called an “irreducibly complex” system. This means that if any of the crucial parts are missing, the whole process breaks down and does not work. How then could this system have evolved through natural gradual processes if all of the pieces must be involved for it to function? Evolutionists can only come up with stories. They offer no evidence as to how this complex system could have arisen. If it is that difficult to come up with an explanation or even a shred of evidence for just one of the many complex systems within the human body, how can anyone believe that the whole body came together by random chance through evolutionary processes?
Did the human body evolve or adapt though natural selection by taking advantage of this clotting feature or was the clotting mechanism in our bodies designed because without it we would be extinct?
The fact that there is even a discussion that the complex system of blood clotting could have been formed by gradual Darwinian evolutionary processes is in itself absurd. Any rational, honest person could never believe that this was the result of anything other than precise engineering by a superior intellect.
Perhaps the process of blood clotting looks designed because it is designed.
 http://www.med. uiuc. edu/hematology/PtClotInfo.htm
 http://en. wikipedia.org/wiki/Fibrin
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