Download Endocrine System

Endocrine System
Endocrine System - Function
The endocrine system is an equally important method of sending
messages within the body for control and coordination of multiple body
systems. The functional unit of the endocrine system is a gland, or a
group of cells that secrete chemicals called hormones. Hormones
circulate throughout the body within the bloodstream and act as longterm messengers. In comparison with neurotransmitters, hormones act
over long distances for a longer time.
Endocrine System - Organs and Structures
The major organs of the endocrine system are:
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Hypothalamus
Pituitary gland
Pineal gland
Thyroid and parathyroid glands
Thymus (note that this gland is also part of the lymphatic system)
Adrenal glands
Pancreas (note that this gland is also part of the digestive system)
Gonads (that is, ovaries or testes—note that these glands are also
part of the reproductive system)
As a specialized part of the brain, the hypothalamus is an endocrine
gland that produces hormones that regulate many basic functions such
as hunger, thirst and sleep through control of the pituitary gland. The
hypothalamus receives sensory input from receptors and perceptual
information from the brain, such as changes in emotional state,
temperature, and lighting.
The pituitary gland is sometimes called the master gland, because it
controls the release of hormones from many other endocrine glands.
The pineal gland secretes the hormone melatonin, which is important
for transmitting information about environmental lighting and inducing
sleep.
The thyroid glands and parathyroid gland are located together in
the neck. The thyroid glands secrete hormones that regulate metabolism
and calcium levels. The parathyroid gland also secretes hormones that
regulate calcium levels.
The thymus gland secrets the hormones thymosin and thymopoietin
that stimulate the production of special lymphocytes (white blood cells)
called T-cells, which play an important role in the immune system by
attacking foreign or abnormal cells.
The adrenal glands produce steroid hormones that regulate
metabolic functions during stress, kidney function, and sexual function.
The adrenal glands also secrete epinephrine (adrenaline) when
stimulated by the autonomic nervous system.
The pancreas secretes insulin, to lower blood sugar levels, and
glucagon to raise blood sugar levels. Therefore, the pancreas is an
important endocrine organ for regulating the fuels available for energy
production by cells.
The gonads, or sex organs (ovaries and testes) secrete sex hormones,
which control production of sperm and eggs as well as other secondary
sex characteristics that are different for males and females. The
secretion of sex hormones by the gonads is under the control of pituitary
gland hormones.
Endocrine System - Anatomy and Direction
The hypothalamus is found deep inside the brain and lies inferior to the
thalamus. The pituitary gland is located at the base of the brain, inferior
to the hypothalamus. The pineal gland is a small gland on the midline at
the posterior of the brain. The thyroid and parathyroid glands lie
inferior to the larynx, around the trachea. The parathyroid gland lies on
the posterior surface of the thyroid gland. The adrenal glands are
located superior to each kidney. The pancreas is located posterior to the
stomach and is connected to the part of the small intestine called the
duodenum. The ovaries are located in the pelvic cavity lateral to the
uterus, while the testes are held external to the abdominopelvic cavity
inside the scrotum.