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This article examines a theory of aging based on the belief that cellular mutations are responsible for much of the aging process.

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Endocrine glands are also known as ductless glands. They secrete hormones directly into the bloodstream. The endocrine glands I in both males and females are the same except for the testis (male) and the ovary (female). The majority of endocrine glands are controlled by the pituitary gland but some are stimulated by the nervous system or by chemical substances.

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Cells are organised throughout the body to increase their efficiency.