Page 133 - Design in Nature

injury. The platelets that become entangled in the location of the injury
release a substance that collects countless others to the same place.
These cells eventually shore up the open wound. The platelets die after
performing their duty in locating the wound. Their sacrifice is only a
part of the coagulation system in the blood.
Thrombin is another protein that facilitates coagulation of blood.
This substance is produced only at the location of the wound. This
production must be neither more nor less than necessary, and has also

to start and stop exactly at the required times. There are more than
twenty body chemicals called enzymes that have roles in the
production of thrombin. These enzymes can trigger its reproduction or
halt it. The process is under so much scrutiny that thrombin only forms
when there is a real wound to the tissues. As soon as the enzymes of
coagulation reach a satisfactory level in the body, fibrinogens that are
composed of proteins are formed. In a very short while, a mesh of fibres
form a web, which is formed at the location of the escaping blood. In the
meantime, patrolling platelets continue to become entangled and
accumulate at the same location. What is called a clot is the plug that is
formed due to this accumulation.
When the wound totally heals, the clot dissolves.
The system that enables formation of the clot, determining its
extent, strengthening or dissolving the formed clot undoubtedly, has an
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absolute irreducible complexity.
The system works flawlessly down to the minutest detail.
What would happen if there were small problems within this
perfectly functioning system? For example, if there was coagulation in
the blood even without a wound, or if the clot could easily break off
from the wound? There is a single answer to these questions: in such
cases the bloodstream to the most vital and intricate organs, such as