The Elements of Blood-Erythrocytes


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The blood is made of:
  • a fluid,
  • the plasma,



  • or the serum and of the formed elements for the blood, or the blood cells.  The plasma is made of proteins-albumin which is the most important, being responsible for the osmotic pressure of the blood and globulins-alfa, beta and gamma; gamma globulines are anitibodies, or the immunglobulins; fibrinogen, which is involved in the blood coagulation. In the plasma are also found small molecule substances, ions and organic salts.



To observe the blood elements or blood cells, are used the blood smears, a blood droplet being spread in a very thin layer on a slide and air-dried. He most common stain method is the Romanovsky technique and ts variants using a mixture of eosin and methylene blue, or derivatives, blended in different proportions.

Erythrocytes (red blood cells)

Erythrocytes are the most numerous cells present on the blood smears, having a round, reddish appearance. The normal concentration of red blood cells in human is about 3.9- 5 million/ml in women and about 4.5-6 million/ml in men. The normal shape of the red blood cell is that of a binconcave disk, resembling to a binconcave lens. This shape is increasing the surface to volume ratio, important in the gases exchanges, which is the main  function of the erythrocytes.The normal dimensions of the red blood cells are about 7.5 micromethres thick, in pheriphery, and only 0.8-1 micrometres in the center, because of its shape.

The content of the red blood cells is represented by

  • 33% hemoglobin (Hb), which is giving the acidophilia of the elements;
  • hemoglobin is made of heme, containing iron and of a protein part , the globine. Hemoglobin is essential in the gases transport, done by erythrocytes; it combines easily with oxygen, forming oxyhemoglobin, with carbon dioxide, forming carbaminohemmoglobin,  but with carbon monoxide is forming an irreversible combination, carboxyhemmoglobin which may lead to severe intoxication.

The cellulaire membrane of the red blood cells was very well studied, because if treated with hypertonic solutions, the content of the cells is expelled and the membrane keep its shape and composition ( the so-called “ghost-cells”)

The composition of the membrane is:

  • Of 50% roteins
  • 40% lipids
  • 10% glucids

The decrease in the number of erythrocytes ar pathologic conditions, generically calld anemias.

Red blood cells are dying after 120 days , being removed by macrphges, especially from the spleen and bone marrow.

By erythropoiesis, bone marrow is providing permanently new erythrocytes, to the circulation blood.

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