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 as "ductless").
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, is enclosed in a capsule 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 for allergic 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 antigen.
The thymus gland is secrets the hormone thymosin.
For a diagram indicating the locations within the body of each of the endocrine glands, see Endocrine Glands of the Human Body.
- Introduction to the Endocrine System
- What is a hormone ?
- Water Soluble Hormones vs Fat Soluble Hormones
- Triggers for Hormone Release
- Hormone Regulation Feedback Mechanism
- Major Glands of the Endocrine System
- The Pituitary Gland
- The Adrenal Glands
- Non-endocrine tissues that release hormones
- Conditions of the Endocrine System