The endocrine system consists of glands,tissues, and individual cells that secrete molecular messengers, calledhormones.
Hormones travel through the body by means of the blood vessels.
When a hormone is released to the bloodstream, itwill eventually interact with a specific cell membrane or cytoplasmic receptorof one or more classes of target cells. Endocrine glands regulate body metabolism,reproductive function, blood electrolytes, growth, blood pressure, uterinecontractions, skin pigmentation, water retention, and blood nutrient levels, aswell as many other functions. There are usually feedback regulation mechanismsbetween hormones and their target cell products and even other hormones. Someendocrine glands, such as the pituitary and adrenal glands, are closely linkedto the nervous system. The endocrine glands include the pituitary, adrenals,thyroid, parathyroids, pancreas, ovaries, testes, and thymus.