The
endocrine system is a collection of ductless glands that secrete chemical
messages, known as hormones.
The role
of the endocrine system is to
maintain homeostasis and long-term
control of the human body using chemical signals (the hormones). Also, the endocrine system works in parallel
with the nervous system to control growth and maturation along with body homeostasis.The
hormones produced by the glands of the endocrine system are passed through the
blood circulation to arrive at a target organ, which possesses a series of cells
that bear an appropriate hormone receptor. This receptor binds with the hormone
molecule and triggers a series of chemical reactions inside the cell. As mentioned before, the endocrine system is
constituted by the endocrine glands – which secrete hormones.
The major endocrine
glands include:- the hypothalamus
- the pituitary
gland
- the thyroid
gland
- the pancreas
- the adrenal
glands
- the gonads
or sex organs
HORMONES
A hormone is a
messenger molecule synthesized and secreted by a group of specialized cells that
constitute an endocrine gland. These
glands are ductless, which means that their secretions (hormones) are
released directly into the bloodstream and travel elsewhere in the body to target
organs, upon which they act. Note that this is in contrast to the exocrine
glands, which have ducts for releasing the substances that they produce.
Exocrine glands (not part of the endocrine system) secrete products that are
passed outside the body. Sweat glands and salivary glands are examples of
exocrine glands.
There
are three general groups of hormones. These are classified as follows –
according to their chemical structure:- Steroid
hormones including prostaglandins
which function especially in a variety of female functions and the sex
hormones all of which are lipids made from cholesterol.
- Amino
acid derivatives (like epinephrine) which are derived
from amino acids, especially tyrosine.
- Peptide
hormones (like insulin) which are the most numerous/diverse
group of hormones.
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