The thymus gland is one of the
endocrine glands of the human body.
Endocrine glands differ from "exocrine" glands
in that exocrine glands have ducts (so may be referred to as "ducted")
whereas endocrine glands do not have ducts (and so may be referred to
It is located across the trachea & bronchi in the
upper thorax (a bi-lobed organ in the root of the neck, above and
in front of the heart).
The thymus is an important component of the immune system and,
and divided internally by cross-walls into many lobules (full of T-lymphocytes).
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 the immune response to microbes and foreign proteins (accounting
response, antoimmunity, and the rejection of organ transplants). T-lymphocytes
migrate from the bone marrow to the thymus, where they mature and differentiate
until activated by
The thymus gland is secrets the hormone thymosin.
For a digram indicating the locations within the body of each of the
endocrine glands, visit:
Glands of the Human Body. This may be of particular interest
to students of courses in massage, reflexology,
beauty therapies, and other basic-level medical or clinical courses.