Hormones

Hormones are chemicals that are manufactured by glands within the body and then released into the bloodstream. From there, the hormones travel to all parts of the body where they influence a wide number of body processes. The glands which collectively make these hormones comprise the endocrine system. This system includes the adrenal glands, the gonads (testes or ovaries), the pancreas, the parathyroid glands, the thyroid gland, and the pituitary gland. In pregnant women, the placenta also functions as part of the endocrine system by making hormones that are released into the bloodstream. Hormones are also made by other organs including the kidneys and the heart, though these organs are not commonly thought of as part of the endocrine system. The process of releasing hormones into the bloodstream is called "exocytosis."