University of Virginia Health System

Red Blood Cell
(Erythocyte, Discocyte, Red Blood Corpuscle)

Peripheral blood smear, Wright-Giemsa stain, 1000x

Description:

Mature red blood cells have a biconcave disc shape, and by light microscopy on a Wright-Giemsa stain of a peripheral blood sample, are round with a central area of palor (about 1/3 of the red cell size), are uniform in size (average diameter of 7.5μm), shape and color, and have no nucleus or mitochrondria. On a peripheral blood smear from a normal subject, they are uniform in size, shape, and color. The size of a normal erythrocyte is approximately the same as that of a nucleus of a very small lymphocyte.

Function:

The major function of red blood cells is to transport oxygen bound to hemoglobin from the lungs to all tissues and organs. Some of the carbon dioxide produced in tissues and organs is also transported bound to hemoglobin to the lungs and released; some is converted to carbonic acid which dissociates, releasing hydrogen ions which shifts the oxygen dissociating curve to the right (Bohr effect), facilitating oxygen release from hemoglobin.

Trafficking:

A newly formed red cell dies by senescence after circulating in the peripheral blood for approximately 120 days. The various changes that the red cell undergoes during aging that lead eventually to removal of the red cell by macrophages located mainly in the spleen are still not completely understood. With aging, the red cell becomes more spherocytic and fragile, leading to a decreased deformability in the microcirculation. As the red cell ages, the capacity to reduce methemoglobin to oxyhemoglobin is decreased due to a decrease in glycolysis. Other mechanisms that lead to phagocytosis by macrophages have been demonstrated: autoantibody formation to antigenic structures exposed on the erythrocyte during aging and the appearance of phosphatidylserine on the outer red cell membrane.

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