SMART TARGET
Teacher Choice
The color of Blood!
QUESTION:
Some of my students
have asked about the color of blood. I am not a
biology person. So, what is the color of blood
inside the body?
Jennifer Miller,
Murfreesboro, Tennessee
ANSWER:
Contrary to popular belief,
the color of blood inside the body, no matter how
you look at it, is red. Blood is bright red when
oxygenated and dark red when it lacks oxygen.
When you look at blood through your skin it may
look blue, but that is the result of how color
wavelengths travel through and are reflected by
the skin. To see a vein at all, light must pass
through the skin and hit the blood in the vein.
The blood then absorbs certain colors of light
and reflects others back through the skin.
In blood, longer, redder wavelengths can go
more deeply into the skin than shorter, bluer
wavelengths before being reflected. Therefore,
a blood vessel below the skin looks blue
because the blue light is reflected.
In reality, blood is either dark or bright red,
depending on the amount of oxygen. Red blood
cells contain hemoglobin, which carries oxygen.
Red blood cells contain hemoglobin, which
carries oxygen. When blood passes through
your lungs, oxygen surrounds the hemoglobin,
turning your blood bright red. Also when blood
is exposed to the oxygen in the air, like when
you cut your finger, it turns bright red. However,
as blood moves through your body to nourish
tissues, which reduces the amount of oxygen in
the blood, it turns a darker shade of red.
American Society of Hematology
Washington, DC
54
The Science Teacher
Now that you are educated on the
color of blood…..
Survey at least 30 people asking,
“What color is blood inside the human
body?” Present your survey results in
a bar graph. Then write a half page,
single-spaced report explaining your
results and what YOU learned.
After you ask the survey participants
about the color of blood, read this
article to them. TEACH THEM!