The definitions used in this glossary of terminology either have been provided by the authors of the articles, or have been extracted wholly or in part, or paraphrased from the following sources: The American Medical Association Encyclopedia of Medicine, Charles B. Clayman, MD, Medical Editor, Random House, New York, 1989; Biotechnology from A to Z, 2d Edition, William Bains, Oxford University Press, New York, New York, 2002; A Dictionary of Genetics, 6th Edition, Robert C. King and William D. Stansfield, Oxford University Press, New York, New York, 2002; Dorland's Illustrated Medical Dictionary, 29th and 30th Editions, W. B. Saunders Company, Philadelphia, 2000, 2003; Genes VII, Benjamin Lewin, Oxford University Press, New York, New York, 2000; The Gale Encyclopedia of Genetic Disorders, Volumes I and II, Stacey L. Blachford, Ed., Thomson Learning, New York, New York, 2002; The Merriam-Webster Dictionary, Merriam-Webster, Inc., Springfield, Massachusetts, 1997; Molecular Biology of the Cell, 3rd Edition, Bruce Alberts, et al., Garland Publishing, 1994; The Random House Dictionary of the English Language, Unabridged Edition, 1966; Webster's Ninth New Collegiate Dictionary, 1991.


1. Any one of the minute protoplasmic masses that make up organized tissue, consisting of a nucleus which is surrounded by cytoplasm which contains the various organelles and is enclosed in the cell or plasma membrane. A cell is the fundamental, structural, and functional unit of living organisms.

2. A small, more or less closed space.

neuroglial cells - The cells of the supportive tissue of the central nervous system (neuroglia); these non-neural cells are of three kinds: astrocytes, oligodendrocytes (collectively termed macroglia) and microglia.

reticular cells - The cells forming the reticular fibers of connective tissue; those forming the framework of lymph nodes, bone marrow, and spleen are part of the reticuloendothelial system and under appropriate stimulation may differentiate into macrophages.

stem cell - 1. Any precursor cell.

2. A blood cell progenitor, or mother cell, having the capacity for both replication and differentiation, and giving rise to various morphologically recognizable precursors of different blood cell lines, such as the proerythrocyte and myeloblast, which cannot self-replicate and must differentiate into more mature daughter cells.