Biconcave disk

A number of refinements and applications are in the literature. Corrections may be made for discreteness of charge [36] or the excluded volume of the hydrated ions [19, 37]. The effects of surface roughness on the electrical double layer have been treated by several groups [38-41] by means of perturbative expansions and numerical analysis. Several geometries have been treated, including two eccentric spheres such as found in encapsulated proteins or drugs [42], and biconcave disks with elastic membranes to model red blood cells [43]. The double-layer repulsion between two spheres has been a topic of much attention due to its importance in colloidal stability. A new numeri-... 

Erythrocytes Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing hemoglobin whose function is to transport oxygen, [nih]... 

Nearly all the oxygen carried by whole blood in animals is bound and transported by hemoglobin in erythrocytes (red blood cells). Normal human erythrocytes are small (6 to 9 pm in diameter), biconcave disks. They are formed from precursor stem cells called hemocytoblasts. In... 

The formed elements of blood are red blood cells, platelets, and leukocytes. Red blood cells, or erythrocytes (Figure 9.2), are flexible biconcave disk-shaped bodies whose main function is to carry oxygen to tissue bound to the hemoglobin that they contain. They are generated in the marrow of various bones by the action of stem cells. The hormone erythropoietin stimulates erythrocyte production in response to tissue needs for oxygen. Marrow stem cells also produce platelets, tiny cell fragments that contain the biochemicals necessary for blood clotting. The third kind of formed elements consists of leukocytes, which are defensive white blood cells. 

Erythrocytes are small compared with most other cells and are peculiar because of their biconcave disk shape (see Fig. 1-12). They have no nucleus, because it is extruded just before the release of the cell into the blood stream from the bone marrow, where the cells develop. Their cytoplasm has no organelles and is full of the protein hemoglobin that binds 02 and C02. In the cytoplasm are other proteins also, namely, (1) the submembrane cytoskeleton, (2) enzymes of the glycolytic and... 

Normal red blood cells are deformable biconcave disks. Their shape is determined by the external environment of the cell, the metabolic activity of the cell, the nature of hemoglobin, the membrane skeleton (see below), and the age of the cell. A normal human red blood cell has a life span of about 120 days and travels a distance of about 175 miles. Much of this travel occurs in capillary channels of the microcirculation, where flow rates are very slow. Here, particularly at branch points, the shape of the cell undergoes striking deformations and can squeeze through openings as small as one-twentieth the cell diameter. Thus, the primary determinant of blood flow and viscosity is... 

The normal red cell is a biconcave disk at rest The average human cell is approximately 7.7 )u.m in diameter and varies in thickness from 2.8 ixm at the rim to 1.4 )u.m at the center [Fung et ai, 1981]. However, red cells vary considerably in size even within a single individual. The mean surface area is 130 /rm and the mean volume is 98 fxw (Table 60.1), but the range of sizes within a population is Gausian distributed with standard deviations of 15.8 m for the area and 16.1 )u.m for the volume [Fung et al., 1981). Cells from different species vary enormously in size, and tables for different species have been tabulated elsewhere [Hawkey et al., 1991). 

Erythrocytes consist of a plasma membrane that surrounds a solution of proteins (mainly hemoglobin) and electrolytes. Mature red blood cells do not contain a nucleus. They are small, about 7-8 micrometers (pm) and shaped like a biconcave disk. Evaluation of red blood cells is important in the diagnosis and monitoring of anemia. 

This section focuses on red cells since most of the particulate volume in human blood is occupied by red cells. Red cells ( erythrocytes ) are biconcave disks under equilibrium conditions in blood plasma as shown in Fig. 61. The diameter of the disk is between 6 and 8 pm. Red cells lack a nucleus and are largely filled with the protein hemoglobin, which binds O2 molecules and several other biologically important molecules. The red cells transport O2 molecules from the lung to tissues throughout the body. They also transport waste products, such as CO2, away from the tissues. 

Water can influence the discharge product morphology [21, 46, 47], and it has been found that concentrations of water in the hundreds to thousands of ppm can promote the formation of biconcave disks see Sect. 3.2.1. 

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