Transcript The Endocrine System

The Endocrine System
• Controls many body
functions
– exerts control by
releasing special
chemical substances into
the blood called
hormones
– Hormones affect other
endocrine glands or body
systems
• Derives its name from
the fact that various
glands release
hormones directly into
the blood, which in turn
transports the
hormones to target
tissues via ducts.
The Endocrine System
• Exocrine glands transport their
hormones to target
tissues via ducts.
• Endocrine
Emergencies:
– from common:
• Diabetes
• to the unusual:
– Thyrotoxicosis
The Endocrine System
• Consists of several
glands located in
various parts of the
body.
• Pituitary gland: a small
gland located on a stalk
hanging from the base of the
brain - AKA
• “The Master Gland”
– Primary function is to
control other glands.
– Produces many
hormones.
– Secretion is controlled by
the hypothalamus in the
base of the brain.
The Endocrine System
• The Pituitary Gland is
divided into 2 areas,
which differ
– structurally and
functionally
– each area has
separate types of
hormone production.
• The two segments are:
– Posterior Pituitary:
• produces oxytocin
and antidiuretic
hormone (ADH)
– Anterior Pituitary:
• produces thyroidstimulating hormone
(TSH)
• growth hormone (GH)
• adrenocorticotropin
(ACTH)
• follicle-stimulating
hormone (FSH)
The Endocrine System
• And even more…
– luteinizing hormone
(LH)
– prolactin
• Let’s go over these
one at a time...
• Posterior Pituitary
– Oxytocin (the
natural form of
pitocin)
• stimulates gravid
uterus
• causes “let down”
of milk from the
breast.
– ADH (vasopressin)
causes the kidney to
retain water.
The Endocrine System
• Anterior Pituitary
– Primarily regulates
other endocrine
glands
– rarely a factor in
endocrinological
emergencies
– TSH stimulates the
thyroid gland to
release its
hormones, thus 
metabolic rate
• Anterior Pituitary…
– Growth hormone
(GH)
•  glucose usage
•  consumption of
fats as an energy
source
– ACTH stimulates the
adrenal cortex to
release its hormones
– FSH & LH stimulates
maturation & release
of eggs from ovary.
The Endocrine System
• The Thyroid Gland
– lies in the anterior
neck just below the
larynyx.
– Two lobes, located
on either side of the
trachea, connected
by a narrow band of
tissue called the
isthmus.
– Sacs inside the
gland contain colloid
• Within the colloid are
the thyroid hormones:
– thyroxine (T4)
– triiodothyronine (T3)
• When stimulated
(by TSH or by
cold), these are
released into the
circulatory system
and  the
metabolic rate.
– “C” cells within the
thyroid produce the
hormone calcitonin.
The Endocrine System
• Calcitonin, when
released, lowers the
amount of calcium in
the blood.
• Inadequate levels of
thyroid hormones =
hypothyroidism, or
Myxedema.
• Myxedema symptoms:
– Facial bloating
– weakness
– cold intolerance
– lethargy
– altered mental
status
– oily skin and hair
– TX: replacement of
thyroid hormone.
The Endocrine System
• Increased thyroid
hormone release
causes
hyperthyroidism,
commonly called
Graves’ disease.
– Signs and
symptoms:
• insomnia, fatigue
• tachycardia
• hypertension
• heat intolerance
• weight loss
– Long term
hyperthyroidism:
• Exopthalmos
– bulging of the
eyeballs (picture
Barbara Bush)
• In severe cases - a
medical emergency
called thyrotoxicosis
can result.
The Endocrine System
• Parathyroid Glands
– small, pea-shaped
glands, located in the
neck near the thyroid
– usually 4 - number can
vary
– regulate the level of
calcium in the body
– produce parathyroid
hormone -  level of
calcium in blood
– Hypocalcemia can
result if parathyroids
are removed or
destroyed.
The Endocrine System
• Pancreas
– a key gland located in
the folds of the
duodenum
– has both endocrine and
exocrine functions
– secretes several key
digestive enzymes
• Islets of Langerhans
– specialized tissues in
which the endocrine
functions of the
pancreas occurs
– include 3 types of
cells:
• alpha ( )
• beta ()
• delta ()
– each secretes an
important hormone.
The Endocrine System
• Alpha () cells
release glucagon,
essential for
controlling blood
glucose levels.
• When blood glucose
levels fall,  cells 
the amount of
glucagon in the blood .
• The surge of glucagon
stimulates the liver to
release glucose stores
(from glycogen and
additional storage
sites).
• Also, glucagon
stimulates the liver to
manufacture glucose • gluconeogenesis.
The Endocrine System
• Beta Cells () release
insulin (antagonistic to
glucagon).
• Insulin  the rate at
which various body
cells take up glucose.
Thus, insulin lowers
the blood glucose
level.
• Insulin is rapidly
broken down by the
liver and must be
secreted constantly.
• Delta Cells ()
produce somatostatin,
which inhibits both
glucagon and insulin.
The Endocrine System
• Adrenal Glands
– 2 small glands that sit
atop both kidneys.
– Each has 2 divisions,
each with different
functions.
• the Adrenal Medulla
secretes the
catecholamine
hormones
norepinephrine and
epinephrine (closely
related to the
sympathetic
component of the
autonomic nervous
system).
The Endocrine System
• One at a time…
• The Adrenal Cortex
secretes 3 classes of
hormones, all steroid
hormones:
– gluticocorticoids
mineralocorticoids
– androgenic hormones
– gluticocorticoids:
– accounts for 95% of
adrenal cortex
hormone production
–  the level of glucose
in the blood
– Released in response to
stress, injury, or
serious infection - like
the hormones from the
adrenal medulla.
The Endocrine System
• Mineralocorticoids:
– work to regulate the
concentration of
potassium and sodium
in the body.
• Prolonged  in
adrenal cortex
hormone results in
Cushing’s Disease.
• Signs & Symptoms of
Cushing’s Disease:
–  in blood sugar levels
– unusual body fat
distribution
– rapid mood swings
The Endocrine System
• And - if there is an 
in mineralocorticoids
as well
– A serious electolyte
imbalance will occur
due to the  potassium
excretion by the
kidney, which results
in hypokalemia.
• Sodium can also be
retained by the kidney,
resulting in
hyponatremia.
– Causes:
• dysrhythmias
• coma
• death
– usually results from a
tumor - TX? Removal
of tumor.
The Endocrine System
• Gonads and Ovaries:
– the endocrine glands
associated with human
reproduction.
– Female ovaries
produce eggs
– Male gonads produce
sperm
• both have endocrine
functions.
• Ovaries:
– located in the
abdominal cavity
adjacent to the uterus.
– Under the control of
LH and FSH from the
anterior pituitary they
manufacture
• estrogen
• protesterone
The Endocrine System
• Estrogen and
Progesterone have
several functions,
including sexual
development and
preparation of the
uterus for implantation
of the egg.
• Testes:
– located in the scrotum
– produce sperm for
reproduction
– manufacture
testosterone • promotes male growth
and masculinization
– Controlled by anterior
pituitary hormones
FSH and LH.
The Endocrine System
• Endocrine
Emergencies:
• Diabetes Mellitus
– one of the most
common diseases in
North America.
–  insulin secretion by
the Beta () cells of
the islets of
Langerhans in the
pancreas.
• Complications of
Diabetes:
– contributes to heart
disease
– stroke
– kidney disease
– blindness
The Endocrine System
• Pathophysiology of
Diabetes:
• Glucose Metabolism
– Glucose (dextrose) is a
simple sugar required
by the body to produce
energy.
– Sugars, or
carbohydrates, are 1 of
3 major food sources
used by the body.
• The other 2 major
food sources are
– proteins
– fats
• Most sugars in the
human diet are
complex and must be
broken down into
simple sugars:
glucose, galactose and
fructose - before use.
The Endocrine System
• Breakdown of sugars
is carried out by
enzymes in the gastro
intestinal system.
– As simple sugars, these
are absorbed from the
GE system into the
body.
– More than 95% enter
the body as glucose.
• To be converted into
energy, glucose must
first be transmitted
through the cell
membrane. BUT - the
glucose molecule is
large and doesn’t
readily diffuse through
the cell membrane.
The Endocrine System
• Glucose must pass
into the cell by
binding to a special
carrier protein on the
cell’s surface.
– Facilitated diffusion doesn’t use energy.
The carrier protein
binds with the glucose
and carries it into the
cell.
• The rate at which
glucose can enter the
cell is dependent upon
insulin levels.
– Insulin serves as the
messenger - travels via
blood to target tissues.
– Combines with specific
insulin receptors on the
surface of the cell
membrane.