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Unlocking blood’s secrets
ne of the first mentions of blood as an important part of the body’s circulatory system may
just be the Ebers Papyrus, a 16th century
B.C. Egyptian medical writing that contains
hundreds of prescriptions and remedies. The
papyrus correctly connects the arteries to the
heart, although it is mistaken in how the arteries carried air
to the rest of the body. The ancient Egyptians didn’t understand that blood was the transport system.
The second century Greek physician Galen was the one who
realized that both arteries and veins carried blood, and he
correctly theorized that the arterial blood transported air.
He mistakenly believed, however, that arterial blood was
created in the heart, while venous blood was created in the
liver. Blood cells are actually created in bone marrow, in an
ongoing process.
Ibn al-Nafis, a 13th century Arabic physician, was the first to
accurately record the process of blood circulation: Deoxygenated venous blood enters the heart’s right atrium, travels from
there to the right ventricle and then through the pulmonary
artery (the only artery to carry deoxygenated blood) into the
lungs. Once the blood has picked up more oxygen, it moves
into the cardiac veins and into the heart’s left atrium. From
there it travels to the left ventricle and then the aorta, which
feeds the blood into other arteries that carry the refreshed
blood to the body’s various cells.
This explanation remained largely unknown in Europe until
1628, when William Harvey published a book about the
circulatory system after conducting a series of experiments.
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The wonders of blood
eople have been finding out more marvels
about blood ever since. And the wonders
keep mounting. Blood carries oxygen to all
the cells in our body—a vitally important
function, to be sure. But it also carries away
carbon dioxide, ammonia and metabolic
wastes. As the one tissue that comes in
contact with every other tissue in the body,
it also allows cells to communicate with one another—a
communications network as well as a transport system. And
it carries the first line of defense, our immune system, to
wherever it’s needed.
The task of carrying oxygen is done by the red blood cells,
which make up about 40 percent of blood’s volume. As they
mature, they give up their own nucleus and DNA in order to
make room for hemoglobin, the proteins that can attach to
the oh-so-necessary oxygen. These cells can squeeze through
capillaries half their width by thinning down into threads and
then crawling along the capillary wall. Dr. Andrew Schafer,
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a professor at Weill Cornell Medical College, compares the
process of their movement through capillaries to tank treads
gripping the ground.
The red cells are accompanied
on their circuitous journey by
white blood cells and platelets.
These are the advance guards of
the immune system. The white
cells look for invading microbes
that carry disease or infection.
When they find something amiss,
they release substances to “call”
other white cells to the area. The
cells then engulf the invaders or
produce antibodies that make the
Laura Rosen
organisms easier to destroy. Red
blood cells outnumber white ones by about 600 to 1.
Blood is a fluid tissue that also thankfully has the ability to
clot and become solid. And that’s where the platelets come
in. Smaller than either red or white cells, the platelets run
along the sides of the endothelium, the tissue that lines
blood vessels. When they detect a break, they stick to it,
attracting other platelets and forming a clump. If the break
is too large for the platelets to control, they call in freefloating proteins that can cross-link to mend the break,
creating a natural Band-Aid.
All of these specialized cells float along in a plasma sea, the
watery substance that comprises about 60 percent of blood.
Plasma contains the sugars, proteins, salts and vitamins
necessary to our cells.
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The need for blood
ooking at all those functions, it’s easy to understand
how vital blood is to our well-being. Unfortunately,
accidents, surgeries, disease and blood disorders
can bring the need for more blood than our bone
marrow can produce. According to America’s Blood
Centers, more than 4.5 million patients need blood
transfusions each year in just the United States
and Canada. Hence there is an enormous need for
people to donate blood.
“Every 25 to 30 minutes, someone in Collier County receives
blood or a blood product,” says Laura Rosen, community
relations manager for the Community Blood Center (CBC),
an affiliate of NCH Healthcare System. “Every donor counts
because only three of every 100 people give blood.”
The CBC came into existence some 60 years ago, after an
Everglades City man had an accident. His friends traveled
to Miami to donate blood. That first blood drive led to the
realization that Collier County needed its own blood supply
Naples Health |
JULY-SEPTEMBER 2009
BLOOD FACTS
Q Someone needs blood every two seconds.
Q There are four main blood types: A, B, AB and O. Each can be
positive or negative. AB is the universal recipient. O negative is the
universal donor for red blood cells.
Q Thirteen tests (11 for infectious diseases) are conducted on
each unit of donated blood.
Q If only one more percent of Americans donated blood, shortages would disappear for the foreseeable future.
ARTIFICIAL BLOOD?
Q Scientists have been exploring the idea of artificially created
blood for decades. While some advances have been made, a safe
and effective alternative has not been found.
Q In 1957, Dr. Thomas Chang (then an undergraduate at McGill
University in Montreal) began to research the creation of artificial
red blood cells. His work helped scientists at Biopure to develop
Oxyglobin, an artificial blood product that treats hemoglobin molecules with glutaraldehyde, a chemical that binds the molecules
together. The company’s polyhemoglobin has been used to replace
blood in aortic reconstruction surgery and to treat anemia patients
in South Africa. It is awaiting FDA approval for use in the U.S.
and donation facility. And that’s what continues to make donating blood
locally so vital.
“Where someone donates does make a difference,” Rosen says. “Most donors understand that giving blood helps to save lives, but it is also vital for
people to question where their blood goes and who it benefits. Blood donors
are a valuable community resource, so it’s important to stress that what is
collected in this community by the Community Blood Center stays in this
community to benefit local patients. Other centers come in periodically for
blood drives, but they are not suppliers to our local hospitals.”
The CBC draws blood from willing donors every day from Estero to Everglades City. Donors can come to either of the organization’s facilities (in
the Medical Plaza Building in Naples and in the Bonita Sunshine Plaza),
but the group also conducts drives at places where people are likely to be
anyway—the Hollywood 20 theaters, for instance.
Eligible donors are anyone who weighs at least 110 pounds, is 17 years
of age or older and is in general good health. There is no upper age
limit. Most common medications and the conditions they treat, such
as high cholesterol or high blood pressure, do not prevent someone
from donating. Individuals who have questions about their eligibility to
donate are encouraged to contact their local donor center for clarification. If an individual is unable to donate, volunteers are always needed
to help organize blood drives.
The CBC endeavors to keep an adequate supply of blood for all the
area’s needs, but Rosen reports it could use 75 to 100 more pints per
week. “We can save three lives with just one pint,” Rosen notes. “All
blood types are great, but we have the highest demand for O+ and O-.”
To find out more about donating blood and keeping it within the community,
visit www.givebloodcbc.org or call (239) 436-5455. Your donation can help
someone’s marvelous transport system keep flowing the way it should.
Naples Health |
JULY-SEPTEMBER 2009
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