Red cells


Red cells

The mature red cells of the blood transport the respiratory gases, oxygen and carbon dioxide (CO2). Oxygen is carried from the lungs to the tissues, where it is exchanged for CO2. Red cells are equipped to perform this function for 120 days during which they make a 300 mile journey around the microcirculation.

Prior to discharge from marrow sinuses into the peripheral blood, red cells shed their nuclei. This gives the advantages of reduced weight and transformation into a biconcave disc with increased deformability compared with the more rigid spheroidal nucleated precursor (Fig 2.1).

The blood volume comprises the mass of red cells and the plasma. Plasma volume is regulated by stretch receptors in the heart and kidney which influence secretion of antidiuretic hormone (ADH) and aldosterone. Erythropoiesis is regulated chiefly by the growth factor erythropoietin.


The mature red cell is around 7.8 µm across and 1.7 µm thick. Its biconcave shape allows maximum flexibility and an umbrella shape is adopted to traverse the smallest capillaries which have diameters of only 5 µm. The ability of red cells to recover from the recurrent stresses of the turbulent circulation hinges on the design of the membrane.

The red cell membrane is composed of a collapsible lattice of specialised proteins (the ‘cytoskeleton’) and an outer lipid bilayer (Fig 2.3

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Jun 12, 2016 | Posted by in HEMATOLOGY | Comments Off on Red cells

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