Imagine being smaller than the period at the end of the sentence. Imagine
being microscopic! Suppose you are almost as tiny as a red blood cell. Picture
your self inside a human heart. You are about to take a guided tour of a human
circulatory system.
Your tour being in the
right at rium of the heart. It is a dark chamber with thin walls. Wow……..Is it crowded!
Millions of blood cells are in the right atrium with you. Most of the cells are
about your size. The guide says that, they are red blood cells “Each one is
shaped like a doughnut with no hole. Most have no nucleus. Every red blood cell
carries a load of carbon dioxide”
The large cell with
nuclei are white blood cell “the guide continues” what are the disk shapes?”
you ask “They are platelets,” the guide answers, “and the yellowish, watery
substance around you is plasma.”
Uh- Oh! What is happening?
The walls of the right atrium seem to be closing in! You bob up and down in the
plasma as you flow through an opening that is like a door. The guide says, “Welcome
to the right ventricle” It is not as crowded.
Thud! The door you
came through closes “Each door in the circulatory system will close after you
go through it. “The guide explain “you can never turn back………… “You begin to
wonder if this tour was a good idea after all. The guide senses your concern
and tells you not to worry “Each time one door closes, another door will open”
As the wall of the
right ventricle close in, another door opens just like the guide said. Swoosh!
You are forced through the door into an artery. You toss and turn in the plasma
as you move through the artery. You feel dizzy.
The Farther you go in
this artery. The more narrow it becomes “We are in the lung capillaries now”
the guide says. “I am not sure I can make it through this narrow passage” You
remark “It is a tight squeeze, but you will make it, “the guide reassures you.
The red blood cells ahead of you squeeze, through the capillaries one at a time.
The guide explains, “The red blood cells are unloading the carbon dioxide they
have been carrying. They will pick up a load of Oxygen from the lungs.
Finally, it is your
turn to go through the capillaries. It was a tight squeeze, but you made it.
Whew! What a relief! The blood vessel is getting wider now, “We are in a vein
that leads back to the heart” the guide says.
Passing through
another door, you find yourself crowded into a small dark chamber again. The
guide says it is the left atrium. The walls begin closing in, but you are not
worried now. Just in time, another door opens and you are forced into a larger
chamber with very thick walls. “Where are we?” You wonder, the guide says, “we
are in the left ventricle. We enter the aorta from here”
The walls of the left ventricle
close in with great force, Spurt! You are forced through a door into the aorta.
You are moving with great speed. Smaller arteries branch off from the aorta.
Plasma, Platelets, and blood cells. Flow in to each of the arteries, looking
ahead, you see that the blood vessel is getting narrow. “Here we go again! The guide
says another tight squeeze through the capillaries. This is where the red blood
cells unload the oxygen they are carrying. They pick up a load of carbon
dioxide from the cells.
You flow out of the
capillaries in to a stream of more plasma of more plasma, platelets, and blood
cells”, we are in a vein on our way back to the heart “the guide says before
you have a chance to ask Splash!
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