Page 132 - Design in Nature

A System Without Room for

Smallest Error: Blood Clotting

Everybody knows that bleeding will eventually stop when
there is a cut or when an old wound starts bleeding again.

Where the bleeding is, a blood clot forms that hardens and heals
the wound in due time. This may be a simple and normal
phenomenon for you, but biochemists have shown through
their research that this actually is the result of a very
complicated system at work. The lack of any one component of
this system or any damage to it would render the whole process
useless.
Blood has to coagulate in the right time and place and
when normal conditions are restored, the clot should vanish.
The system functions flawlessly down to the minutest detail.
If there is bleeding, the clot should form immediately in
order to prevent the creature from dying. Furthermore, the clot
should cover the entire wound and, more importantly, should
only form over, and remain right on top of, the wound.

Otherwise all the blood of the creature could coagulate and
cause its death, which is why the clot should form at the right
time at the right place.
The smallest elements of the bone marrow, the blood
platelets or thrombocytes, are crucial. These cells are the main
elements behind the coagulation of blood. A protein, called the
Von Willebrand factor, ensures that, in their continuous patrol of
the blood stream, these platelets do not miss the place of the