thymus
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.
DEFINITION:
- thymus
-
A gland that forms part of the immune system. The thymus is situated in the upper part of the chest, behind the breastbone, and consists of two lobes that join in front of the trachea. Each lobe is made up of lymphoid tissue consisting of tightly packed lymphocytes, epithelium, and fat.
The thymus plays a part in the body's immune response from about the 12th week of gestation until puberty. The gland gradually enlarges until puberty, when it begins to shrink. Lymphoid and epithelial tissues are gradually replaced by fat, although some glandular tissue remains until after middle age.
The function of the thymus is to cause lymphocytes to become T cells. These T cells play an important part in the body's defense against viruses and other infections.
DISORDERS:
Abnormal enlargement of the thymus sometimes occurs in several conditions, including myasthenia gravis, acromegaly, thyrotoxicosis, and Addison's disease. Myasthenia gravis is also sometimes associated with thymomas (tumors of the thymus). In children, immunodeficiency disorders may arise as a result of abnormal development of the thymus.
Used in 1 Article translation
Used in 1 Article translation