Why is my blood blue
What Color is Blood REALLY? (6 min version)
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this last February I posted a video
about red blood cells and the heart it
was a short little clip that followed
several blood cells as they went through
the heart got oxygen and delivered it to
the rest of the body I'm so blue when I
don't have o to it's time to go to the
heart and right after I posted it one of
my patrons replied that she thought I
might like to know that human blood was
never blue now before we go further I
want you to consider what you believe
about blood and why is what always red
is it red when it has oxygen but blue
when it doesn't have oxygen what
evidence do you have to support your
opinion
and now I'll tell you why I thought
blood was blue when I was a kid
several adults told me that blood was
blue without oxygen I remember a teacher
in elementary school saying that if you
were bleeding in outer space your blood
would be blue because there wouldn't be
any oxygen the idea of bleeding blue and
outer space is super catchy and I
remembered it and as I grew up certain
things seemed to confirm the idea that
blood was blue I could see my veins
which had a bluish tint to them I
learned that if someone was hypoxic and
lacking oxygen their lips and their beds
of their nails would turn bluish and I
saw that babies if they were born not
breathing well had a dusky or a bluish
tint to their skin and there were those
illustrations in anatomy and physiology
textbooks Venus flow was always blue an
arterial flow was always red all of
these things supported the idea that
blood was blue when it didn't have
oxygen but several times I was exposed
to a powerful counter example when I had
blood drawn it went into a small vial
that didn't have any oxygen inside it
and the blood that went directly from my
veins into this vial was not blue it was
a dark red now I knew that the vial was
vacuumed and had no oxygen and I knew
that the color was dark red but here's
the amazing thing I did not even notice
the contradiction this is called
confirmation bias when you have an
opinion or belief a lot of times your
brain will ignore contradicting evidence
but not consciously I didn't look at
this counter example and think that
strange I have decided I'm going to
ignore it it was a subconscious decision
that I didn't even realize I had made so
I thought blood was blue when it didn't
have oxygen right up until one of my
patrons made that comment on the
Valentine's video it made me wonder how
many other people thought the blood was
blue how widespread was this
misconception so I carried my camera
around with me for several weeks and I
interviewed as many people as I could
this was a non scientific non-random
survey but the results that I got looked
something like this almost half of the
people I interviewed thought the blood
was blue but I also had answers
ranging from black to white to brown to
purple I got a huge variety of answers
everywhere I went except for one place
at United Blood Services every single
phlebotomist there said that blood with
that oxygen was dark red or maroon
phlebotomist work with blood every day
so their opinion has quite a bit of
validity when it comes to what color
blood is here you can see venous blood
that has come directly from a vein and
gone into a vacuumed vial that had no
oxygen the blood in the collection bag
is quite dark and color but if you look
up where the air bubble is you can see
that the blood has a reddish hue maroon
and burgundy are good descriptions for
this color
so this is a really interesting question
something that almost everybody agrees
is a dark red maroon burgundy color
looks blueish under certain conditions I
found a great answer in a peer-reviewed
scientific journal called applied optics
in this article the researchers went
into a great amount of detail they
talked about photons the particles that
make up light and why we perceive colors
the way we do in the article researchers
described how they had tubes of venous
blood to represent veins and then tubes
of blood that had 100% oxygen to
represent arteries they put both of
these tubes underneath a translucent
barrier that was meant to mimic skin and
then they measured the light and they
found that both a vein or an artery will
appear blue or turquoise when they are
of a certain size and at a certain depth
underneath the skin but if the tubes
were smaller than a certain diameter or
too deep they would not appear blue so
this is really cool if your arteries
were close to the surface and big enough
they would look blue too but your body
has a practical design arteries are deep
inside you and veins are close to the
surface because if you cut a vein you
can fix it with a band-aid whereas if
you cut an artery
you need a tourniquet and maybe surgery
it's pretty cool to know that both
arteries and veins with a blue under the
right conditions but where does the blue
color come from in the first place well
remember that white light is made up of
all the wavelengths of color
the reason veins can appear blue is
because the tissue absorbs more red
light and so the light that's reflected
back out has a larger percentage of blue
again this is something that only works
if the skin is a certain pigment and the
vein is a certain diameter and it's
within a certain distance from the
surface does this mean that you'll never
find blue blood no several animals have
blue blood including armadillo DM
vulgari the potato bug spiders octopus
squid and mollusks and their blood is
blue because they don't use hemoglobin
to carry oxygen they use hemocyanin
which contains copper instead of iron as
a binding agent
so there is such a thing as blue blood
but for humans and every other
vertebrate blood is always red if you
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subscribe as always work hard grow smart
and I'll see you next time
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