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The Endocrine System
Major functions of the
Endocrine System
 By releasing chemicals called hormones into
the bloodstream, Endocrine glands control:
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Metabolism
Growth
Development
Puberty
Tissue function
Mood
Exocrine vs. Endocrine
Endocrine Glands
Exocrine Glands
Secrete into the blood
Secrete into the external
environment or an organ
Have ducts
Ductless (no ducts)
Secrete hormones
Secrete other stuff
(sweat, oil, enzymes
etc.)
The Endocrine System:
a Gland System
 Endocrine glands utilize
blood vessels to transport
hormones as a means of
regulating hundreds of
physiologic processes,
maintaining homeostasis.
Endocrine Glands
The Hypothalamus
 The hypothalamus is an
incredibly complex portion of
the midbrain which bridges
the gap between the nervous
system and the endocrine
system. It secretes a number
of different “releasing”
hormones which, in turn,
activate Pituitary Gland
function.
The Hypothalamus (cont.)
 The Hypothalamus is connected to the pituitary via a
funnel shaped stalk called the infundibulum.
 In addition to ‘releasing hormones,’ the hypothalamus
secretes inhibitory hormones which halt the
secreation of various stimulatng hormones into the
capillary beds of the pituitary.
Endocrine Glands:
The Master Gland
 About the size of a walnut, the Pituitary
Gland receives messages from the
hypothalamus and releases many different
hormones into the bloodstream in response.
 These hormones target other glands,
organs and/or tissues usually elliciting a
cascade of responses.
Pituitary Gland Hormones
Hormone
Abbreviation
Target
Effect
Growth Hormone
GH
Bones and muscles
Growth/ cell
reproduction
Prolactin
N/A
Mammary Glands
Milk production
Adrenocorticotropic
Hormone
ACTH
Adrenal Glands
Releases
androgens
Melanocyte
Stimulating Hormone
MSH
Melanocytes
(in the dermis)
Produces melanin
Follicle Stimulating
Hormone
FSH
Ovaries/Testes
puberty
Luteinizing Hormone
LH
Ovaries
ovulation
Oxytocin
N/A
Uterus
Uterine contraction
during pregnancy
Antidiuretic Hormone
ADH
Kidneys
Water retention
Thyroid Stimulating
Hormone
TSH
Thyroid
Metabolism
regulation
Pituitary/Hypothalamus Interaction
Classification of Hormones:
3 Basic Categories
EXAMPLES
 The simplest group of hormones
are modified amino acids.
 Hormones may also include much
more larger and intricate protein
complexes.
 Finally, some lipid hormones are
considered steroids, and actually
diffuse across cell membranes.
The Pineal Gland
 The pineal gland is
about the size of the tip
of your little finger, and is
located deep inside the
brain.
 Secretes melatonin,
which regulates sleep
patterns.
 Its other functions remain
a mystery….
Did You Know?...
 The Pineal Gland is the smallest of all your
organs.
The Thyroid Gland
 Located at the base of the
throat, and shaped like a
butterfly, the Thyroid Gland is
actually 2 glands in one…
 Secretes the hormone
thyroxine to regulate
metabolism of
carbohydrates, fats, and
proteins in the bloodstream.
Iodine is an integral element
in this hormone.
 Secretes calcitonin to
regulate Calcium (Ca+) and
phosphate ion levels in blood
and bone.
The Thyroid (cont.)
 C Cells- (extrafollicular
cells): Calcitonin
 follicular cells
surrounding lumen filled
with thyroglobulin T3, T4
The Parathyroid glands
 Embedded in the posterior surface of the thyroid, there are 4
raisin sized parathyroid glands.
 Parathormone (PTH) governs osteoblast and osteoclast
activity, while aiding the thyroid maintaining appropriate calcium
concentration in the blood.
Challenge Question:
 What is a
“goiter?”
The Thymus Gland
 the thymus is located in the
upper anterior portion of the
chest cavity just behind the
sternum. Its primary function is
to provide an area for Immune
cell maturation, and is vital in
immune system development.
The thymus secrets a
hormone called Thymosin,
which controls T-Lymphocyte
maturation.
The Pancreas
 The Pancreas acts as
both an endocrine and
an exocrine gland. Its
endocrine function
regulates blood sugar
levels by releasing
insulin (lowers blood
sugar) and/or glucagon
(raises blood sugar) into
the bloodstream.
The Adrenal Glands
 Located on the top of the kidneys, the adrenal
glands secrete adrenaline and cortisol.
 These hormones initiate the “Fight or Flight”
response as part of the sympathetic nervous
system.
Adrenal Glands (cont.)
 Cortex
 Zona glomerulosa: mineralcorticoids
 Zona fasciculata: glucocorticoids
 Zona reticularis: sex steroids
 Medulla:
epinepherine and
norepinepherine
The Testes
 testes are components of both
the reproductive system and the
endocrine system. The respective
functions of the testes are:
 producing sperm
 producing male sex hormones of
which testosterone is the bestknown.
 Testosterone is responsible for the
appearance of secondary sex
characteristics in males.
The Ovaries
 Just like the testes, the
ovaries have both a
reproductive function
as well as endocrine.
Estrogen is responsible for the
appearance of secondary sex
characteristics in females at puberty
as well as the development and
maintenance of the reproductive
organs
 Producing eggs
 Secretion of estrogen
and progesterone
The Endocrine System and
Interdependence:
Negative Feedback Loops
 The primary function of the
Endocrine System is to
maintain homeostasis
(equilibrium) among all
body systems by using
“negative feedback” to
control hormone secretion.
Negative Feedback: Blood Sugar
Negative Feedback: Calcium
Negative Feedback: Temperature
Negative
Feedback:
Metabolism
Practice Quiz:
Name These Glands
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