adrenal gland

adrenal gland defined in 1951 year

adrenal gland - adrenal (suprarenal) gland;
adrenal gland - An organ of hormone secretion in vertebrates. There is a single pair, one near each kidney, in man and other mammals; but there are multiple adrenals in many other vertebrates. In all tetrapods each gland has two components, distinct in function but closely fused together, (a) Medulla, the inner part of the gland in mammals, embryologically derived from nervous tissue (neural crest), secreting adrenaline and noradrenaline. Its activity is controlled by the sympathetic nervous system. Medullary tissue seems to have largely an emergency function, secreting its hormones when the animal is driven to fight or flee; it is not essential for a quiet life, (b) Cortex, the outer part of the gland in mammals, embryologically derived from the lining of the coelom. It secretes various steroid hormones, which fall into three classes, though there is some overlapping of function: sex hormones, especially androgens, in both sexes of mammals; glucocorticoids, including cortisone and hydrocortisone, which promote carbohydrate formation from fat and protein, and have other effects; and mineralocorticoids, especially aldosterone, which control the salt and water balance of the body. Cortical hormone (especially glucocorticoid) secretion is controlled by a pituitary hormone (See also: ACTH). The adrenal cortex is indispensable for life. Medullary (=chromaffin) tissue and cortical (=interrenal) tissue are variously arranged within the adrenal of non-mammalian vertebrates; in many fish they are separated into distinct organs.

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