The Endocrine

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The Endocrine
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Collected by Aj .Thanaporn
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Learning Goals

• By the end of this unit, you will be able to
• differentiate between the endocrine and
  exocrine glands.
• discuss differences among the various
  endocrine glands,
• the hormones they produce, and
  their functions.
• explain how negative and positive feedback
  mechanisms
• regulate hormonal levels. .

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• recognize common disorders of the endocrine
  system.
• investigate a career option within the context
  of
• Anatomy and Physiology.

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What Is the Endocrine System? The foundations of
the endocrine system are the hormones and
glands. As the body's chemical messengers,
hormones (pronounced hor-moanz) transfer
information and instructions from one set of
cells to another.
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Although many different hormones circulate
throughout the bloodstream, each one affects
only the cells that are genetically programmed
to receive and respond to its message. Hormone
levels can be influenced by factors such as
stress, infection, and changes in the balance of
fluid and minerals in blood.
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A gland is a group of cells that produces and
secretes, or gives off, chemicals. A gland
selects and removes materials from the blood,
processes them, and secretes the finished
chemical product for use somewhere in the body.
Some types of glands release their secretions in
specific areas. For instance, exocrine
(pronounced ek-suh-krin) glands, such as the
sweat and salivary glands, release secretions in
the skin or inside of the mouth.
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Endocrine glands, on the other hand, release more
than 20 major hormones directly into the
bloodstream where they can be transported to
cells in other parts of the body.
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The major glands that make up the human endocrine
system are the hypothalamus, pituitary, thyroid,
parathyroids, adrenals, pineal body, and the
reproductive glands, which include the ovaries
and testes.
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The pancreas is also part of this
hormone-secreting system, even though it is also
associated with the digestive system because it
also produces and secretes digestive enzymes.
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Although the endocrine glands are the body's main
hormone producers, some non-endocrine organs -
such as the brain, heart, lungs, kidneys, liver,
thymus, skin, and placenta - also produce and
release hormones.
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Hypothalamus The hypothalamus is
located in the lower central part of the
brain. This part of the brain is important in
regulation of satiety, metabolism, and body
temperature. In addition, it secretes hormones
that stimulate or suppress the release of
hormones in the pituitary gland.
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The tiny pituitary is divided into two parts the
anterior lobe and the posterior lobe. The
anterior lobe regulates the activity of the
thyroid, adrenals, and reproductive glands. Among
the hormones it produces are
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The pituitary gland may be king, but the power
behind the throne is clearly the hypothalamus.
As alluded to in the last section, some of the
neurons within the hypothalamus - neurosecretory
neurons - secrete hormones that strictly control
secretion of hormones from the anterior
pituitary. The hypothalamic hormones are
referred to as releasing hormones and inhibiting
hormones, reflecting their influence on
anterior pituitary hormones.
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Hypothalamic releasing and inhibiting hormones
are carried directly to the anterior pituitary
gland via hypothalamic-hypophyseal portal veins.
Specific hypothalamic hormones bind to receptors
on specific anterior pituitary cells, modulating
the release of the hormone they produce.
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As an example, thyroid-releasing hormone from the
hypothalamus binds to receptors on anterior
pituitary cells called thyrotrophs, stimulating
them to secrete thyroid-stimulating hormone or
TSH. The anterior pituitary hormones enter the
systemic circulation and bind to their receptors
on other target organs. In the case of TSH, the
target organ is the thyroid gland.
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1. What is the "Master Gland? 2. This gland
secretes antidiuretic hormone (ADH). 3.
This gland secretes insulin. 4. Hormones from
this gland help regulate 5. This gland
secretes thyroid stimulating
hormone (TSH). Hint It't not the
thyroid
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6. This gland secretes Oxytocin (OT). 7. This
gland secretes epinephrine and norepinephrine. 8.
This gland helps regulates circadian rhythms,
such as sleep-wake cycles, and seasonal cycles
of fertility in many mammals. 9. This gland
secretes cortisol and aldosterone . 10 . This
gland secretes Growth Hormone (GH).
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The Quiz 1. One of the hormones secreted by the
islets Langerhans is. calcitonin
insulin growth hormone
parathyroid hormone
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2. Which gland secretes insulin?
gonads thyroid pancreas
posterior pituitary 3. Which gland secretes
melatonin? adrenal cortex
parathyroids pineal pancreas
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4. Which gland secretes luteinizing hormone (LH)?
adrenal cortex pancreas
pineal anterior pituitary
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5. The two hormones released by the posterior
pituitary are antidiuretic hormone and
oxytocin prolactin and oxytocin prolactin
and growth hormone testosterone
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6. All endocrine cells --secrete hormones that
travel through the blood stream to target
cells.---secrete hormones that travel through
the nervous system to target cells.---travel
through the nervous system to target
cells.---travel through the blood stream to
target cells.
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www.biologie.uni-hamburg.de/b-online/library/falk/
Endocrine/ endocrine.htm
www.kidshealth.org/parent/general/body_basics/ end
ocrine.html
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