The human body is an amazing thing!
If blood didn’t circulate through our
bodies, carrying oxygen and nutrients,
we wouldn’t be able to live. Blood is so
important to life that the body
constantly makes new blood.
Producing Blood
To do this, the body must produce the
liquid part of blood, called plasma, and
the cells that float in it. Plasma is made
mostly of water and salts that we
absorb through our digestive tracts
every day. Its job is to deliver nutrients
and water throughout the body.
Ninety-nine percent of the blood cells
floating in plasma are red blood cells,
which carry oxygen from the lungs to
the rest of the body and give blood its
red color. The average life of a red
blood cell is four months.
What Happens After That?
The spleen continuously destroys
millions of old red blood cells, recycling
the iron to make new red cells. White
blood cells, which are part of the
immune system, and platelets, which
help with blood clotting at a site of
injury, also float in plasma. They have
much shorter life spans than red cells
and also are replaced continuously.
If you’ve ever seen a bone cut
crosswise, with soft tissue called
marrow inside, then you’ve seen where
blood cells are made. Bone marrow
contains special blood cells, which
constantly divide to produce new cells
to replace the ones that have been
destroyed. Why all this bloody business
in the bone marrow? The body’s
process of forming new blood cells
helps you recover if you lose blood to
an injury, and it also helps blood
perform its many functions despite cell
damage and loss.
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