Gland: A gland that secretes hormones directly into the blood. These glands make up the endocrine system.
Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Many hormones are secreted by special glands. Hormones are essential for every activity of life, including the processes of digestion, metabolism, growth, reproduction, and mood control.
Endocrine System: The endocrine system chemically controls the various function of cells, tissues, and organs through the secretion of hormones. The endocrine system includes the adrenal glands, parathyroid gland, pituitary gland, and thyroid gland, as well as the ovaries, pancreas, and testes.
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