Wiktionary
n. (context anatomy English) Any of various glands that secrete hormones directly into the blood or lymph and not through a duct.
WordNet
n. any of the glands of the endocrine system that secrete hormones directly into the bloodstream [syn: endocrine, ductless gland]
Wikipedia
Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary gland are neuroendocrine organs. Local chemical messengers, not generally considered part of the endocrine system, include autocrines, which act on the cells that secrete them, and paracrines, which act on a different cell type nearby.
The ability of a target cell to respond to a hormone depends on the presence of receptors, within the cell or on its plasma membrane, to which the hormone can bind.
Hormone receptors are dynamic structures. Changes in number and sensitivity of hormone receptors may occur in response to high or low levels of stimulating hormones.
Blood levels of hormones reflect a balance between secretion and degradation/ excretion. The liver and kidneys are the major organs that degrade hormones; breakdown products are excreted in urine and feces.
Hormone half-life and duration of activity are limited and vary from hormone to hormone.
Usage examples of "endocrine gland".
It is, speaking in terms of evolution, the oldest endocrine gland in the human body.
This fact seemed to indicate that there was an unknown hormone involved that certain lower types possess an endocrine gland which is either atrophied or non-existent in higher types.