Download 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.

Exocrine glands transport their
hormones to target
tissues via ducts.

Endocrine
Emergencies:
 from common:
▪ Diabetes
▪ to the unusual:
▪ Thyrotoxicosis

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 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)

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.

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 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.
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.

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.

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.

Pancreas

Islets of Langerhans
 a key gland located in
 specialized tissues in
the folds of the
duodenum
 has both endocrine and
exocrine functions
 secretes several key
digestive enzymes
which the endocrine
functions of the
pancreas occurs
 include 3 types of cells:
▪ alpha ( )
▪ beta ()
▪ delta ()
 each secretes an
important hormone.
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.

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.


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 Adrenal Cortex
secretes 3 classes of
hormones, all steroid
hormones:
 gluticocorticoids
mineralocorticoids
 androgenic hormones
One at a time…
 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.

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

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.


Gonads and Ovaries:

Ovaries:
 the endocrine glands
 located in the abdominal
associated with human
reproduction.
 Female ovaries produce
eggs
 Male gonads produce
sperm
cavity adjacent to the
uterus.
 Under the control of LH
and FSH from the
anterior pituitary they
manufacture
both have endocrine
functions.
▪ estrogen
▪ protesterone

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.
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
Pathophysiology of
Diabetes:
 Glucose Metabolism


 proteins
 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
 fats

Most sugars in the
human diet are
complex and must be
broken down into
simple sugars: glucose,
galactose and fructose
- before use.

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.

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.