What are red blood cells?
Red blood cells (also called erythrocytes) provide a blood red color. There are so many red blood cells in the blood (about 25 billion) which makes them responsible for the red color of the blood.These tiny, round and flattened discs, all at the same time circulate through our bodies and are always found in the blood vessels.
It is almost impossible to imagine such a large number, but this may help you to understand it:
Each blood cell is so small that it can be seen only under a microscope.
If we can connect these microscopic cells into a series, than we could encircle the globe four times!
However, during blood tests, only blood cells from one spatial millimeter of blood are counted, not from the whole body.
Although these cells are very small, together they cover a huge area.
For example, if you have woven them into the carpet, its total area would amount to 4,500 square meters. Given that at any moment one-fourth of blood is in the lungs, an area of about 1,100 square meters of red blood cells is constantly exposed to the air.
What do red blood cells do?
When in the bone marrow, a red blood cell grows and becomes mature, it loses its nucleus and contains more hemoglobin.Hemoglobin is red pigment or color and it contains iron in combination with proteins.
When blood passes through the lungs, oxygen binds to the hemoglobin of red blood cells.
Red blood cells carry oxygen through the arteries and capillaries to all cells of the body.
Carbon dioxide from the cells of the body goes through the veins to the lungs in the same way, usually combined with hemoglobin.
From where originate these blood cells?
Apparently, the "factory" in which is created such enormous amount of cells “the bone marrow” must have such amazing productivity - especially when we take into account that, sooner or later, each of these cells dissolves and it is replaced by a new one!Red blood cells live only about four months and then fall apart, mostly in the spleen.
Human bone marrow is adapted to their need for oxygen.
At high altitudes it produces more red blood cells, and at low altitudes less. People who live on mountain tops may have nearly double the number of red blood cells than people who live on the coast!
The number and size of red blood cells, in a human being depends on one's need for oxygen.
Worms do not have blood cells.
Cold-blooded animals - reptiles – are have relatively large and numerous blood cells in their blood.
Small, warm-blooded animals, which live in mountainous areas, have the highest number of red blood cells.
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