THE HUMAN ENDOCRINE SYSTEM
Section I. INTRODUCTION
ENDO = internal
CRINE = secrete
a. The endocrine glands are glands of internal secretion (rather than external,
as seen with the sweat glands and digestive glands).
b. This internal secretion results from the fact that these glands have no ducts.
Thus, they are often referred to as the ductless glands.
c. The secretions produced by the endocrine glands are called hormones.
d. Hormones are carried by the bloodstream to specific organs or tissues,
which are then called the target organs.
e. The activity of the target organ, in turn, affects the activity of the endocrine
organ. Thus, it is a reverse or feedback mechanism.
a. Control "Systems" of the Human Body. The structure and function of the
human body is controlled and organized by several different "systems."
(1) Heredity/environment. The interaction of heredity and environment is
the fundamental control "system." Genes determine the range of potentiality and
environment develops it. For example, good nutrition will allow a person to attain his full
body height and weight within the limits of his genetic determination. Genetics is the
study of heredity.
(2) Hormones. The hormones of the endocrine system serve to control the
tissues and organs in general. (Vitamins have a similar role.) Both hormones and
vitamins are chemical substances required only in small quantities.
(3) Nervous system. More precise and immediate control of the structures
of the body is carried out by the nervous system.