Blood moves through
a closed circuit of veins
and leaks out in case of
even a slight cut.
However, it is of great im-
portance for our health to
stop its flow. You may
have heard of people who
die of excessive blood loss
in accidents or opera-
tions. Well then, what
causes blood to stop flow-
ing a little while after a
wound starts to bleed?
This is called blood
clotting, which is one of
the automatic security
systems in our bodies.
Some substances existing
in the blood stop and
close the wound. Thanks
to the clotting ability of
blood, excessive bleeding
is prevented. As shown in
58
A cut on your hand or a wound on your knee
heals in a short time. The pictures above
show some of what happens in your blood
vessels during this healing process.
Blood leaks through the wound.
Blood surrounding the wound coagulates.
Cells close up the wound like a plug.
red blood cell
platelet
damaged
skin
blood clot
