is the endocrine system?
Humans have two
systems of internal communication: the nervous system and the endocrine
system. The endocrine system controls the delivery of messages through
the release of chemicals known as hormones. Hormones are secreted
directly into the blood by endocrine glands.
glands are found throughout the body and are responsible for
releasing more than 50 hormones.
Endocrine glands include the pituitary,
and parathyroid, pancreas,
and the gonads (ovaries
In pregnant women the placenta also functions as an endocrine
gland becoming the principle site of steroid production during
The hormones produced by endocrine glands may be either proteins
or steroids such as the sex steroids: estrogen, progesterone
For more detailed
information on the endocrine system, go to the "science
and issues" section.
For a more
graphical and animated illustration of the endocrine system, go
the "endocrine primer"