An organ that is part of the lymphatic system, in which T lymphocytes grow and multiply. The thymus is in the chest behind the breastbone.
A gland that enables cells of the immune system of mammals to mature. In humans, it lies behind the breast bone and extends upwards as far as the thyroid gland. The thymus is the place in the body where T lymphocytes are “taught” to distinguish “foreign” (e.g., pathogen’s) antigens from “self” cell antigens, to avoid immune responses in which the body’s immune system attacks organs and other cells within the body (resulting in autoimmune diesease). Any T lymphocytes that remain “autoreactive” (i.e., would tend to attack “self” cells, such as organs in the body) are destroyed by the thymus via a cytotoxic mechanism. An example of an autoimmune disease is multiple sclerosis (MS), where the body’s acetylcholine receptors are attacked by the body’s immune system. Since acetylcholine is crucial in the transmission of nerve impulses to the body’s muscles, such destruction of acetylcholine receptors resuhs in loss of control of the body’s muscles.
An endocrine gland in the front part of the top of the thorax, behind the breastbone.
A gland in the upper chest that is part of the lymphatic system, the network of vessels and organs that functions as a filter in the body’s immune system, protecting against disease.
Bilobed gland situated below the thyroid gland and behind the sternum and involved in the function of the lymphatic system and the immune system. The gland increases in size until puberty; thereafter it becomes smaller and decreases in functional activity during adulthood.
A lymph organ located in the antero-superior mediastinum.
A two-lobed organ of lymphatic tissue located under the top of the sternum (breastbone) near the end of the trachea (windpipe). The thymus is central to the immune system and the development of white blood cells. One type of white blood cell, the T cell, is produced in the red bone mar¬ row and matures in the thymus, from which its name derives.
A bilobed organ in the root of the neck, above and in front of the heart. The thymus is enclosed in a capsule and divided internally by cross walls into many lobules, each full of lymphocytes (white blood cells associated with antibody production). In relation to body size the thymus is largest at birth. It doubles in size by puberty, after which it gradually shrinks, its functional tissue being replaced by fatty tissue. In infancy the thymus controls the development of lymphoid tissue and immune response to microbes and foreign proteins (accounting for allergic response, autoimmunity, and rejection of organ transplants). Its function in the adult is unclear.
A lymphoid organ located in the mediastinal cavity anterior to and above the heart, composed of two fused lobes each containing multiple lobules roughly divided into an outer cortex and inner medulla. Immature T cells (thymocytes) make up most of the cortex and some of the medulla. The remaining cells are epithelial cells, with some macrophages. Epithelial cells in some areas of the medulla develop hard cores and are known as Hassall’s corpuscles; their purpose is unknown.
An endocrine gland located in the upper chest, that helps to develop the body’s defenses against infection.
A gland positioned in the anterior region of the neck that plays a vital role in coordinating the development of the immune system.
A gland located in the upper front part of the chest. It enlarges until approximately the second year of life, remains stable until around the age of fourteen, after which it undergoes fatty changes and gradually diminishes. Its specific function is not clearly understood.