ENDOCRINE SYSTEM ::
There are two types of glands in the body :(1) Exocrine glands and (2) Endocrine glands
Exocrine glands possess the ducts through which secretions are poured externally via ducts Salivary glands lachrimal glands gastric glands etc are the examples of the exocrine glands
Endocrine glands are the ductless glands which pour their secretions directly into the blood These glands are richly supplied with blood and their secretions are named as hormone (Endo=inside Crinos = secretions ) Endocrine system forms a part of the communication system of the body and provides an alternative method of communication with the nervous system
Hormones are the chemical messengers secreted in small amounts by the endocrine glands which travel all over the body via blood to affect distant organs Chemically hormones may be peptides (anterior pituitary hormones insulin and glucagon ) steroids (adrenocortical and gonadal hormones ) amines (adrenaline and noradrenaline ) or derivatives of aminoacids (thyroxine)
Characteristics of hormones ::
1.Action in low concentration : Hormones act in very low concentrations like the vitamins
2.Storage metabolism and excretion : Hormones are usually synthesized and stored in the gland itself (except for posterior pituitary hormones which are synthesized in hypothalamus but stored in posterior pituitary gland ) They are rapidly destroyed after their functions are over and hence they do not have any cumulative action
3. They never produce new action but modify the physiological functions of the body in other words they have a regulatory role on the physiological functions
4. Distant target organs :: Hormones usually produce their effects at the target organs in the body situated far away from the glands
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