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The Collaborative International Dictionary

thymus \thy"mus\ (th[imac]"m[u^]s), a. [NL., fr. Gr. qy`mos.] (Anat.) Of, pertaining to, or designating, the thymus gland. -- n. The thymus gland.

Thymus gland, or Thymus body, a ductless gland in the throat, or in the neighboring region, of nearly all vertebrates. In man and other mammals it is the throat, or neck, sweetbread, which lies in the upper part of the thorax and lower part of the throat. It is largest in fetal and early life, and disappears or becomes rudimentary in the adult. The thymus gland functions as the site of maturation of T-lymphocytes (T-cells), which confer cell-mediated immunity on the host organism; thus, removal or malfunciton of the thymus can lead to absence of cell-mediated immunity, and a consequent loss of resistance to infection.

Douglas Harper's Etymology Dictionary

gland near the base of the neck, 1690s, Modern Latin, from Greek thymos "a warty excrescence," used of the gland by Galen, literally "thyme," probably so called because of a fancied resemblance to a bud of thyme (see thyme). Related: Thymic.


n. (context anatomy immunology English) A ductless gland, consisting mainly of lymphatic tissue, located behind the top of the breastbone. It is most active during puberty, after which it shrinks in size. It plays an important role in the development of the immune system and produces lymphocytes.


The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells or T lymphocytes mature. T cells are critical to the adaptive immune system, where the body adapts specifically to foreign invaders. The thymus is composed of two identical lobes and is located anatomically in the anterior superior mediastinum, in front of the heart and behind the sternum. Histologically, each lobe of the thymus can be divided into a central medulla and a peripheral cortex which is surrounded by an outer capsule. The cortex and medulla play different roles in the development of T-cells. Cells in the thymus can be divided into thymic stromal cells and cells of hematopoietic origin (derived from bone marrow resident hematopoietic stem cells). Developing T-cells are referred to as thymocytes and are of hematopoietic origin. Stromal cells include epithelial cells of the thymic cortex and medulla, and dendritic cells.

The thymus provides an inductive environment for development of T cells from hematopoietic progenitor cells. In addition, thymic stromal cells allow for the selection of a functional and self-tolerant T cell repertoire. Therefore, one of the most important roles of the thymus is the induction of central tolerance.

The thymus is largest and most active during the neonatal and pre-adolescent periods. By the early teens, the thymus begins to atrophy and thymic stroma is mostly replaced by adipose (fat) tissue. Nevertheless, residual T lymphopoiesis continues throughout adult life.

Thymus (plant)

The genus Thymus (; thymes) contains about 350 species of aromatic perennial herbaceous plants and subshrubs to 40 cm tall in the family Lamiaceae, native to temperate regions in Europe, North Africa and Asia.

Stems tend to be narrow or even wiry; leaves are evergreen in most species, arranged in opposite pairs, oval, entire, and small, 4–20 mm long, and usually aromatic. Thyme Flowers are in dense terminal heads, with an uneven calyx, with the upper lip three-lobed, yellow, white or purple.

Several members of the genus are cultivated as culinary herbs or ornamentals, when they are also called thyme after its best-known species, Thymus vulgaris or common thyme.

Thymus species are used as food plants by the larvae of some Lepidoptera ( butterfly and moth) insect species, including Chionodes distinctella and the Coleophora case-bearers C. lixella, C. niveicostella, C. serpylletorum and C. struella (the latter three feed exclusively on Thymus).

Thymus (insect)

Thymus is a genus of hymenopteran insects of the family Eulophidae.

Thymus (disambiguation)

Thymus may refer to:

  • Thymus, an organ
  • Thymus (plant) a genus of plants in the Lamiaceae family
  • Thymus (insect), a genus of insects in the Eulophidae family

Usage examples of "thymus".

Linsmayer reported a case in which there was a softened adenoma in the pituitary body, and the thymus was absent.

A second possibility arises from the fact that the thymus is composed of lymphoid tissue, very like that of the spleen, the tonsils, and the lymph nodes.

It has seemed possible, therefore, that the thymus shared the functions of such lymphoid tissue and, one way or another, combatted bacterial infection.

There is a series of organs in the body which has long puzzled physiologists,--organs of glandular aspect, but having no ducts,--the spleen, the thyroid and thymus bodies, and the suprarenal capsules.

The thymus glands, sweetbreads, are collected in a plastic bag until he has enough for a meal.

One is tempted to think that the thymus might produce some secretion which, like the juvenile hormone of insects, keeps a child from maturing.

It has seemed possible, therefore, that the thymus shared the functions of such lymphoid tissue and, one way or another, combatted bacterial infection.

Two that continue to arouse a great deal of attention involve the thymus organ and the pineal gland.

Removal of the thymus in very young mice also makes it possible for the creature to accept skin grafts from other animals.

If the thymus inserts are from another strain of mice, skin grafts from that other strain will still be accepted.

I put it into a flat spiral motion, forcing it to move downward through my spleen and my solar plexus, up into the suprarenals, the thymus.

Occasionally in the past there were speculations as to the effect on adolescence, and the changes that took place at this time, of the thymus gland (from a Greek word of uncertain derivation).

The thymus gland lies in the upper chest, in front of the lungs and above the heart, extending upward into the neck.

Hans Weatheral, a youth of some ninety years and still adolescent in appearance through a hyper-active thymus gland, was one of her charges.

The heart, which looked like a strapped-down slab of red meat, the pathetically deflated lungs, the thymus gland—.