人体内的腺体分为两大类:一类是有管腺或称外分泌腺,如消化腺、汗腺等,它们的分泌物是通过导管输送到体表、呼吸道和消化道粘膜表面的;另一类是无管腺,它们的分泌物是直接进入血液而被运送到全身各器官的组织细胞而起作用的,故称内分泌腺,如甲状腺、甲状旁腺、肾上腺、胰岛、脑垂体及性腺等。内分泌腺分泌的生物学活性物质称为激素。从化学结构上可将它们分为两大类:一类属于类固醇激素,如肾上腺皮质激素、性激素,这类激素不能被消化酶所分解,故在临床做药用时可以口服;另一类是含氮激素,如甲 Glands in the human body is divided into two categories: one is the possession of glands or exocrine glands, such as digestive glands, sweat glands, their secretions through the catheter to the body surface, respiratory and gastrointestinal mucosal surface; the other One is the absence of tube glands, their secretions directly into the bloodstream is transported to the body tissues and organs of various organs and play a role, so that endocrine glands, such as thyroid, parathyroid, adrenal, islet, pituitary and gonads Wait. Secretion of endocrine glands biologically active substances known as hormones. From the chemical structure can be divided into two categories: one is a steroid hormone, such as adrenal cortex hormones, sex hormones, these hormones can not be digested by the digestive enzymes, it is clinically useful for oral medicine; the other is Nitrogenous hormones, such as A