SCIENCE • HUMANS & BLOOD
Humans & blood AUTHOR: MIKAIL YILMAZ
14
Blood is necessary for humans. Without it, we
The science of blood
In humans, blood is composed
would be cold, pale, and of course, dead.
Blood is essential to life –
of 55% plasma (water +
Blood is a vital fluid in our bodies where it
almost all animals have it.
protein), 40% red blood cells
circulates in a complex network of arteries
Even insects have an
(RBC), and the remaining 5%
and veins. The significance of blood in the
analogous liquid called
is platelets and white blood
human mind can be appreciated by the marks
hemolymph. The blood’s main
cells. The characteristic red
it has left in our culture: contracts were
role is to help distribute
color of blood is attributed to
sealed with blood; consumption of blood is
nutrients and oxygen to every
the RBCs, which are discoid
forbidden in Judaism because it’s considered
cell in our body so they have
cells that contain the iron-
to be sacred; “bloody” is a common
the energy needed to survive.
based protein hemoglobin as
intensifying word in British English; warriors
In contrast, single-celled
the oxygen-binder. All
drank the blood of their enemies; many
organisms (e.g. bacteria, and
vertebrates have red blood,
traditional folk remedies include blood as an
fungi) and animals with high
from sharks to birds. In
ingredient; there are stories of vampires with
surface/volume ratio and slow
contrast, crustaceans, spiders,
an endless taste for blood; and for more than
metabolism (e.g. sponges,
and octopuses have blue
2,000 years, bloodletting was the dominating
corals, and jellyfish) can rely
blood because their blood
treatment in the doctor’s arsenal of remedies.
on passive diffusion of
contains the copper-based
However, the greatest impact of human’s
nutrients and oxygen from
protein hemocyanin as the
fascination with blood has been the
water to their body. Thus,
oxygen-binder. Moreover, the
discoveries of the blood’s biological
these animals don’t need
breakdown of RBCs gives rise
properties, which have benefited millions of
blood. Similarly, one part of the
to the colors in bile, urine, and
human lives.
human body is in direct contact
stool. A similar color transition
with the air and can get oxygen
can be seen in contusions
by passive diffusion without the
(commonly known as bruises):
need for blood – the cornea of
first red, then blue, then green,
the eye.
then yellow, and lastly brown.
medicor • 2021 | ISSUE 1
