Plasma, Blood

the fluid portion of the blood. Plasma contains the formed elements of the blood—erythrocytes, leukocytes, and thrombocytes. It is a colloidal solution of inorganic compounds and such organic compounds as proteins; it also contains more than 20 vitamins and 20 trace elements, including iron, phosphorus, calcium, zinc, and cobalt. Plasma analysis is of great use in diagnosing various diseases. For example, the diagnostician looks for abnormal proteins, such as the C-reactive protein in rheumatism. Various diseases can be detected by an increase in the content of normal blood constituents; for example, hyperglycemia, which is the abnormally high content of sugar in the plasma, is symptomatic of diabetes mellitus. Increase in the titers of certain antibodies can also serve as a diagnostic clue in certain diseases. The medicinal substances albumin, dried blood plasma, fibrinogen, and gamma globulin are prepared from blood plasma.

Figure 1. Schematic representation of plasma types: (a) a gaseous plasma, (b) an electron plasma in a metal, (c) an electron-hole plasma in a semiconductor. The shaded circles are neutral atoms, the small solid circles represent mobile electrons, the large white circles with plus signs represent ions, and the small white circles represent conduction holes.