Red blood cells

Figure14. SEM of the erythrocytes

Erythrocytes, which are anucleate, are packed with the 0₂ carrying protein hemoglobin (Hb). Under normal conditions, these cells never leave the circulatory system. The normal number of the erythrocytes for the women is 3,7-4,9×10¹²/L, and for the men is 3,9-5,5×10¹²/L.

Most mammalian erythrocytes are biconcave disks without nuclei. There are some other shapes of the erythrocytes, such as spherical, flat, plane and branched. This phenomenon is called poikylocytosis. There are 2 types of it. It is called physiological poikylocytosis when 80% of red blood cells have shape as biconcave disk and 20% other shape. And it is called pathological poikylocytosis when more than 20% of erythrocytes have other shape.

Figure15. Erythrocyte dimensions

Human erythrocytes are 7-8μm (micrometer) in diameter, 2, 6 μm thick at the rim and 0, 8 μm thick in the center.

A decreased number of erythrocytes in the blood are usually associated with anemia. An increased number of erythrocytes are called erythrocytosis or polycythemia.

Erythrocytes with diameters greater than 9 μm are called macrocytes, and those with diameters less than 6 μm are called microcytes. The presence of a high percentage of erythrocytes with great variations in size is called anisocytosis.

Erythrocytes are surrounded by a plasmalemma. It consists of about 40% lipid, 50% protein and 10% carbohydrate. Erythrocytes contain in their interiors about 33% of hemoglobin, the 0₂ carrying protein that accounts for their acidophilia.

Hb consists of four polypeptide chains complexed to iron-containing heme groups. Hb is designated as HbA, HbA₂ and HbF. Adult Hb is about 96% HbA, 2% HbA₂ and 2 % HbF. HbF is the principal form of Hb in the fetus.

Main functions are:

-the transport of oxygen from the lungs to the tissues of the body

-the transport of carbon dioxide from the tissues of the body to the lungs

Дата добавления: 2015-07-25