Page 22 - Human anatomy COMPLETELY DONE1

Figure 15. Formed Elements of Blood

RED BLOOD CELLS
Erythrocyte cells lose their nucleus during maturation. Inside the erythrocytes
are molecules of bright red respiratory pigment - hemoglobin, more than 250 million
molecules in each cell. It is hemoglobin that makes blood red, and red blood cells are
called red blood cells. Normally, 1 mm 3 of blood contains about 5 million red blood
cells. Erythrocytes have a discoid, biconcave shape. This form provides the largest
contact surface with the smallest volume. Red blood cells can penetrate into the thinnest

capillaries, quickly giving off oxygen.
The main function of red blood cells is to transfer oxygen from the respiratory
organs to all cells of the body and to remove carbon dioxide from the tissues.
The erythrocyte cell has been in the blood for about four months. Old red blood
cells are destroyed in the liver or spleen. New red blood cells are formed in the red bone
marrow located in the spongy bone substance.
The hemoglobin molecule consists of two parts: protein – globin and iron–
containing - heme. In the lungs, hemoglobin is able to easily attach oxygen. The
compound of hemoglobin with oxygen has a bright red color.
Blood saturated with oxygen is called arterial. The connection of hemoglobin
with oxygen is unstable. When it disintegrates, hemoglobin and free oxygen are formed
again, which enters the tissue cells. Oxygen-depleted blood is called venous.
WHITE BLOOD CELLS
Leukocytes are colorless, they are called white blood cells, have nuclei. 1 mm3 of blood
contains 4-9 thousand leukocytes. Their number can fluctuate greatly, increasing with

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