Download Endocrine system

Endocrine system
Kaiu Prikk 2015
Lecture 9
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Endocrine system:
- all organs of the endocrine system are glands
- provides control by hormones secreted into and circulated
by the blood
2 types of glands: exocrine & endocrine
1) Exocrine glands: deliver secretions through a duct to
specific locations (salivary glands, sweat glands, mucous
glands)
2) Endocrine glands: are ductless; secrete hormones into
intercellular spaces
Endocrine organs: hypothalamus, pituitary, pineal, thyroid,
parathyroid, thymus, adrenal, pancreas, ovary & testes.
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Location of the endocrine glands
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Hormones:
- chemical messengers
- bind to target cells & affect cell activities
- enter the bloodstream and are carried throughout the body to
affect a variety of tissues and organs
Hormones: steroid & nonstreoid hormones
Steroid hormones:
- produced from the lipid-cholesterol
- are able to pass through cell membranes, bind to receptor
proteins.
Nonsteroid hormones:
- are made from amino acids
- generally cannot pass through the cell membrane.
- bind to a receptor site on the outside of a cell in order to
initiate chemical reactions inside the cell.
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Target organs or tissues - the sites in the body that each
hormone effects
Some hormones have many targets while others only one or
a few target organs
the response of the body to hormones is slower & more long
lasting (than the response to nerve impulses)
Controlled by: 1) negative feedback; 2) antagonistic
hormones
A negative feedback: blood glucose levels  pancreas release
insulin  insulin promotes the entry of glucose into cells  blood
glucose levels the pancreas stops secreting insulin.
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Pituitary gland
- located at the base of the brain, below the hypothalamus
-the hypothalamus secretes releasing/inhibiting factors
that affect the release of substances from the pituitary
gland
2 glands:
1) anterior pituitary gland or adenohypohysis which is a
separate gland
2) posterior pituatry gland or neurohypophysis which is
actually an extension of the nerve tissue of the hypothalamus
Adenohypohysis:
4 tropic hormones: stimulate another endocrine gland to
grow and secrete hormones
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Acromegalia
-results from the excess production of growth hormone (GH)
in the anterior lobe of the pituitary gland.
- is characterized by enlarged facial features, enlarged jaw,
enlarged frontal bone of skull, widely spaced teeth and
enlargement of the bones of the extremities
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Thyroid Gland
Located on the front and sides of the trachea just below the
larynx
Hormones:
Thyroxine: target organ is all tissues
stimulates energy production and protein synthesis.
Released as a result of TSH from anterior pituitary
Calcitonin- lowers the blood calcium levels
Helps maintain normal level of calcium in blood & maintains
stable, strong bones
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The Parathyroid Glands
a. four glands located on the surface of the thyroid gland
b. secretes Parathyroid hormone (PTH) or parathromone
c. raises blood calcium levels; is an antagonist to calcitonin
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The adrenal glands
1. two glands located cranial to each kidney
2. consist of a cortex and medulla
The adrenal cortex secretes
a) mineralocorticoids
b) glucocorticoids
c) androgens
The adrenal medulla secretes
a) epinephrine
b) norepinephrine
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Adrenal Cortex –
Secrete 3 types of hormones
1. Aldosterone the most abundant of the mineralocorticoids;
targets the kidneys;
maintains sodium and potassium blood levels
2. Cortisol is the major glucocorticoid; increases the use of fat
and excess amino acids for energy
3.Sex Hormones -promotes secondary sexual characteristics
(male androgens & female estrogens)
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The Pancreas
1. located in the upper left region of the abdominal cavity
2. has both exocrine (digestive) and endocrine functions
3. the endocrine functions of the pancreas maintains blood
glucose levels
4. the pancreas secretes insulin and glucagon
5. hormone producing cells of the pancreas are called the
islets of Langerhans
Insulin - lowers blood glucose levels & promotes formation of
glycogen by the liver
Target organs liver, muscles & other body cells
Glucagon - raises blood glucose level by stimulating the liver
to change glycogen to glucose.
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The thymus
- a lobular gland that lies just beneath the sternum
- predominant in young
- secretes thymosin (T-Lymphocyte transformation)
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Ovaries
Estrogen - is secreted by the ovary; promotes maturation
of the ovum and prepares the uterus for the fertilized egg;
responsible for secondary sexual characteristics in
women - breasts, pubic hair, body shape
Progesterone - produced by the corpus luteum of the
ovaries; stimulated by LH from the pituitary gland
-inhibits the pituitary gland from stimulating follicle
development during pregnancy
-helps prepare mammary glands for milk production
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Testes
Testosterone - promotes maturation of sperm
-stimulates development of secondary sexual
characteristics at puberty
-growth of reproductive organs, facial & pubic hair,
- “voice change” due to the growth of larynx & body
shape
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Pineal gland
located in the brain
a hormone: melatonin
-is involved in daily cycles or circadian
rhythms.
Levels are high at night & low at day light
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Diagnostic technologies:
1. Blood analysis
2. Sonography
3. CT
4. Biopsy
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Endocrinology - Overview
https://www.youtube.com/watch?v=YcPicFL5Jnw
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