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Hormone (from the Greek hormān = to stimulate, setting in motion) is a product of a gland with inner secretion (endocrine gland). It is a substance which acts as a signal molecule conducting information from one tissue to another. Hormones are transported throughout the body by the bloodstream.

Secretin was the first hormone identified in the human body (in 1902, by the English physiologists Ernest Starling and William Bayliss).

Hormones are produced in special glands. These glands can be found in various parts of the body. They are transmitted to their target cells through the bloodstream. Endocrine glands (glands without ducts) are responsible of production and release of the majority of hormones. They are called this way because they release their products directly into the bloodstream (unlike the exocrine ones).

How hormones work[edit | edit source]

Nervous and endocrine systems are two systems which are responsible for controlling the human body. Hormones have a much slower effect in comparison to nerves. Most of the hormones which play role in basic body functions, such as growth and reproduction, act very slowly. In general, hormones are associated with controlling or influencing chemical processes in target cells. For example, by determining the rate at which they use nutrients to generate energy, or whether or not these cells will produce milk, hair, or other products of metabolic processes in the body.

Hormones have various effects. Hormones produced in endocrine cells have a general effect (e. g.: insulin and sex hormones). There are also hormones with a local effect – e. g. secretin. Secretin is produced in duodenum in response to the presence of food in the duodenum. Secretin is transported through the blood to the pancreas and encourages a release of an aqueous juice that contains enzymes needed for the digestion.

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