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.”
