What is the endocrine system; what are the categories of organs that comprise the endocrine system? Name those organs that play both an endocrine and non-endocrine role in the body. What role do hormones play in the body? At what levels are hormones effective; how do they reach their target organs?
The tissues of the endocrine system function to secrete chemical messengers known as hormones. The organs comprising the endocrine system can be divided into two broad categories: those that serve functions in addition to their role as hormone secretors and those that serve only to secrete hormones. There are relatively few endocrine tissues that also have non-endocrine functions: the gonads, the pancreas, the pyloric mucosa of the stomach, and the mucosa of the duodenum. While all cells release chemicals capable of affecting other cells, hormones are released in a regular manner by tissues specialized for their production and have very specific effects on specifically targeted tissues in the body. Thus, hormones are the chemical control mechanisms by which the endocrine system regulates numerous life functions in the body. Hormones are secreted and effective at very low concentrations due to their stimulus at their cellular targets of enzyme activity which carries out the actual cellular response to hormone stimulation. Hormones, which often target tissues that are far removed from the hormones' sites of secretion, are carried to their target sites
