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ENDOCRINE SYSTEM
Endocrine Glands
 A gland is any organ that produces a
secretion.
 Endocrine glands are groups of tissues which
produce hormones from materials already
present in the blood or lymph.
FUNCTION OF THE ENDOCRINE
SYSTEM
 Hormones act as chemical messengers. They
coordinate and direct activities of target cells
and organs throughout the body.
 Major glands of endocrine system
 pituitary
 pineal
 pancreas
- thyroid
- parathyroid
- gonads
- thymus
- adrenals
FUNCTION OF THE ENDOCRINE
SYSTEM
HORMONAL CONTROL
Remember Negative feedback
 occurs when there is a drop in the level of a
hormone
 triggers a chain reaction of responses to increase
hormones in the blood
This feedback mechanism continues until the
correct level of hormone is found present in the
blood.
 Endocrine gland disturbances may be caused
by:
 Disease
 Infection
 Hyperactivity
 Hypoactivity
PITUITARY GLAND
 Located at the base of the brain and
connected to the hypothalamus
 Divided into anterior and posterior lobes
 Known as the master gland because of its
major influence in body’s activities
Hormones of the Anterior Lobe
The anterior pituitary lobe is larger of the two
lobes; it produces seven hormones:
 Growth hormone
 Thyroid stimulating hormone
 Prolactin hormone
 Adrenocorticotropic hormone
 Follicle stimulating hormone
 Interstitial cell-stimulating hormone
 Luteinizing hormone
Growth Hormone (GH)
 Is responsible for growth and development of
bones and muscles.
 Also helps fat to be used for energy (this
preserves glucose levels)
Prolactin hormone (PRL)
 Develops breast tissue and stimulates the
production of milk after childbirth.
 The function in males is not known.
Tropic Hormones
Thyroid stimulating hormone (TSH)
 Stimulates the growth and secretion of the
thyroid gland.
Adrenocorticotropic hormone (ACTH)
 Stimulates growth and secretion of the adrenal
gland.
Follicle-stimulating hormone (FSH)
 Stimulates the development of eggs in
females.
 Stimulates the production of sperm in males.
Hormones of the Pituitary Gland
The posterior pituitary lobe:
 Stores hormones produced by the
hypothalamus:
 vasopressin
 oxytocin
Vasopressin
 Changes into antidiuretic hormone (ADH)
when it enters the bloodstream.
 Maintains a water balance by increasing the
amount of water that is absorbed by the
kidneys.
 Results in decreased urinary output and
increased blood volume.
Oxytocin
 Released during childbirth.
 Causes strong contractions of the uterus.
THYROID GLAND
 Located in the lower portion of the anterior neck; just
below the “Adam’s apple”.
 Secretes 3 hormones:
 Triiodothyronine (T3)
 Thyroxine (T4)
 Calcitonin
Remember TSH?
 These hormones are produced when thyroid
stimulating hormone triggers the thyroid to
become active.
 The first 2 hormones require iodine to work
properly.
 The iodine for these hormones comes from the
diet it combines with the AA tyrosine to form T3
and T4
 T 3 and T4 controls the rate of cellular metabolism
throughout the body.
Calcitonin
 Controls the calcium ion concentration in the
bloodstream.
 High levels of calcium ions in the blood stimulate
the release of calcitonin.
 Ca+ is then stored in bones and calcium
concentrations in the bloodstream decreases.
PARATHYROID GLANDS
Four glands attached to posterior
surface of the thyroid
Secrete parathormone (PTH)
Parathormone
 Extracts Ca+ from bones to correct low
blood calcium levels.
 Stimulates an increase in number and size
of osteoclasts (bone-demineralizing cells)
THYMUS GLAND
 Is located deep to the sternum.
 The thymus secretes a large number of hormones;
the major one is thymosin.
Thymosin
 Stimulates the lymphoid cells which are
responsible for the production of Tcells an
important part of the immune system.
ADRENAL GLANDS
 There are two adrenal glands one is located on
top of each kidney.
 The hormones of the adrenal glands are known as
corticoids.
1. Mineralocorticoids – (aldosterone):
causes Na+ and water to be absorbed into
the bloodstream and increases blood
pressure.
2. Glucocorticoids (cortisone and cortisol) – main job is
to increase the amount of glucose in the
bloodstream.
step 1: Converts proteins and fats in the liver into
glycogen.
step 2: Breaks down glycogen into glucose as
needed.
3. Epinephrine (adrenalin)
Released in response to stress.
Increases the heart rate and helps the liver
release glucose for energy needs.
Considered the “fight or flight” hormone
GONADS – sex organs
Ovaries – in females, found at the end of each
Fallopian tube; produces:
 estrogen for female characteristics and
progesterone which prepares the uterus for
implantation.
Testes - male sex organ; found in the scrotum
sac; produces:
 Testosterone for male characteristics.
PANCREAS
 Located posterior to the stomach
 Pancreas as an endocrine gland produces:
1. insulin - a hormone that promotes the uptake of
glucose by cells
2. glucagon - a hormone that causes the liver to
breakdown stored glycogen and release it as
glucose into the bloodstream
PINEAL GLAND
 Located posterior to the diencephalon
 Produces the hormone melatonin
Melatonin
 Amount of light entering the eye affects the
amount of melatonin secreted
 The darker it is, the more melatonin produced.
The lighter it is, the less melatonin produced.
 Causes low body temperature & sleepiness
ENDOCRINE GLAND
DISORDERS
DISORDERS OF THE ENDOCRINE
SYSTEM
 Endocrine gland disturbances may be caused
by:
 Disease
 Infection
 Hyperactivity
 Hypoactivity
PITUITARY DISORDERS
 Hyposecretion of growth hormone during
childhood will result in:
Pituitary Dwarfism = body proportions are normal,
but the person has max height of 4’.
2’ 5”
< 2’
PITUITARY DISORDERS
 Hypersecretion of growth hormone during
childhood, prior to the ossification of the
epiphyseal growth plates, will result in:
Gigantism = body proportions are normal, but
the person reaches a height of 8 to 9 feet.
8’ 11.5”
8’ 1.5”
PITUITARY DISORDERS
 Hypersecretion of GH after the long bones have
finished growing will result in:
Acromegaly = the facial bones (lower jaw and
ridge of brow), hands and feet enlarged
tremendously.
PITUITARY DISORDERS
 Hyposecretion of ADH (made from vasopressin)
leads to:
Excessive urine output called diabetes insipidus.
People with this problem are continually thirsty
and drink huge amounts of water.
THYROID DISORDERS
 Hyposecretion of the thyroxine due to a lack of
iodine in diet.
 The thyroid works overtime to try to make the
T3 and T4 hormones. Results in:
Hypothyroidism = is evidenced by the presence of
a goiter.
THYROID DISORDERS
 Hyposecretion of thyroxine during childhood.
Would be due to a lack TSH; results in:
Cretinism = a type of dwarfism where the
body retains childlike proportions (the upper
body is larger than the lower body. Often
results in mental retardation.
THYROID DISORDERS
 Hypersecretion of thyroxine (usually results
from a tumor on the thyroid gland); results in:
Hyperthyroidism also known as Grave’s
disease.
Evidenced by rapid heartbeat, nervous or
agitated behavior, and bulging eyes.
Exopthalmos = bulging eyes
PARATHYROID DISORDERS
Hyposecretion of parathormone:
Low levels of calcium affects the nerves and cause
uncontrollable muscle spasms known as tetany.
Hypersecretion of parathormone:
 Calcium is taken from the bones in excess, weakening
the bones.
 The calcium is deposited in the kidneys resulting in
kidney stones
Kidney stones
ADRENAL DISORDERS
 Hyposecretion of the adrenal cortex due to
adrenal insufficiency or to a lack of ACTH from the
pituitary gland.
 Addison’s disease = skin appears “bronzed”, muscle
weakness, and weight loss.
PANCREATIC DISORDERS
 The decreased secretion of insulin or the
ineffective use of insulin by cells.
Diabetes mellitus = results in high blood glucose
levels.