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:9: Endocrine System
Glands
A gland is composed of a cluster or accumulation of cells. Every gland might be likened to a chemical factory in which all cells are working and the production of the factory is their secretions. Some glands, such as those of the skin and the gastro-intestinal tract, produce secretions which drain out to the surface or into a body cavity via a duct and affect only near where they are released. These are called exocrine glands (exo=outside). They are-liver, pancreas, kidneys, salivary glands etc.
In contrast, the endocrine glands (endo=inside) , specialized organs, ductless and their production passes directly into the blood-stream, circulates all over the body and acts at places far from where it originated.
We have already dealt with the important exocrine glands in the previous chapters. In this chapter we shall, therefore, deal with the ductless endocrine glands, their secretions called hormones and their profound effects on the physical functions, mental states and behavioural patterns of an individual. Unlike continuous anatomical structures of most of the systems of the body, the glands of the endocrine system are scattered through the body like islands. Nevertheless, they are unified into a finely coordinated system, function in a marvellously harmonious fashion and coordinate the activities of the body.
Endocrinology is one of the latest and the fastest developing areas of bio-medical research. The endocrine system, at its simplest, works like a thermostat. Just as, the thermostat may instruct the central heating to switch on or off, the endocrine system regulates various functions of the vital organs of the body to match the external conditions,
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