Many adults living in the US become curious about doctor prescribed growth hormone replacement therapy when they begin to experience chronic symptoms, such as low energy, fatigue and low sex drive, that are frequently associated with your bodyâs declining growth hormone levels.
External, or exocrine, secretion is distinguished from internal, or endocrine, secretion. In external secretion the products elaborated by a gland are released into the external environment; the secretion first enters the glandular duct, from which it is discharged onto the surface of the body or into hollow organs.
Endocrine glands are also called ductless glands, because they secrete hormones directly into the bloodstream. In contrast, exocrine glands release their secretions through ducts (for example, the sweat glands produce fluid that flows to the skin's surface through tiny tubelike sweat ducts). Hormones can be considered chemical messengers. They are targeted at specific cells in the body, and their arrival in those cells causes specific activities to occur. One of the major tasks of hormones is to coordinate the activities of organ systems.