Endocrine system

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Systems of Human Body
• When a bunch of organs work together on one big
project, that’s called a system.
– Skeletal
– Digestive
– Muscular
– Lymphatic/Immune
– Endocrine
– Nervous
– Reproductive
– Urinary
– Cardio-vascular
© 2012 NOVA IVI FERTILITY |

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Glands
• A Gland is a group of cells or tissue that produces and secretes
or gives off chemicals.
Exocrine Glands
Eg: Sweat Gland, Salivary Gland
Endocrine Glands
Eg: Pituitary , Thyroid etc.
Glands
Releases their
secretions through
ducts
Releases their
secretions directly in
blood stream

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Endocrine Glands
1 1
2
2
4
2
2

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Hormone
• Hormone is a chemical substance that is secreted into the body
fluid by cells & that exerts a physiological control effect on
other cells of the body. Hormones transfer information and
instructions from one set of cells to another.
• The endocrine system is instrumental in regulating mood,
growth and development, tissue function and metabolism as
well as sexual function & Reproductive processes.

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Properties of Hormone
• Hormones are informational molecules.
• Hormones are highly specific in nature.
• Hormones stimulate or inhibit specific biological process.
• The effect of hormones is slow and lingering.
• Their deficiency may lead to serious consequences.
• Hormones show feed-back mechanism.

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Classification of Hormone
Hormones
Steroid Hormones
Eg Cortisol, Estrogen
Derivatives of Amino
Acid
Eg.Epinephrin
Proteins or Peptides
Eg. Insulin,Growth
Hormones

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Hormone Receptors
• These are specialized proteins capable of binding the
hormone molecule with very high specificity and affinity.
• Receptor proteins are present either on surface of a cell
or in its interior.
• Down Regulation : Binding of receptors by hormone leads
to decrease in the number of receptors, which decreases
the response of target tissue to hormone.

9© 2012 NOVA IVI FERTILITY |
Hormone Receptors

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Mode of Action
Receptor inside
the cell
cytoplasm
Receptor on the
surface of the
cell membrane
All hormones acts by binding to
specific receptor proteins in the
target tissue cells.

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Hypothalamus
• The hypothalamus is a collection of specialized cells that is
located in the lower central part of the brain.
• Is the main link between the endocrine and nervous
systems.
• Nerve cells in the hypothalamus control the pituitary
gland by producing chemicals that either stimulate or
suppress hormone secretions from the pituitary.

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Hormone Secreted by Hypothalamus
• Thyrotropin-releasing hormone (TRH)
• Gonadotrophin-releasing hormone (GnRH)
• Growth hormone-releasing hormone (GHRH)
• Corticotropin-releasing hormone (CRH)
• Somatostatin (Growth factor-inhibiting hormone)
• Dopamine

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Pituitary Gland
• It is unpaired, pea shaped, small gland about 1 cm, in diameter
& 0.5 to 1 gram in weight
• Connected to the hypothalamus by the pituitary stalk
• Divisible into
a.Anterior Lobe (Adenohypophysis)
b.Posterior Lobe (Neurohypophysis
• It is also called as hypophysis (from Greek, “lying under”)

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Pituitary Gland

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Hormones Function
• Growth Hormones
• Thyroid Stimulating
Hormone
• Adrenocorticotropic
Hormones
• Prolactin
: Promotes Growth,
Controls Metabolism
: Stimulates growth and
activity of thyroid gland
: Synthesis of cortisols
: Stimulation of Lactation
Anterior Lobe (Adenohypophysis)

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• Gonadotrophic Hormones
 Follicle Stimulating
Hormone
 Luteinizing Hormone
: In females, controls the
growth of ovarian follicle.
: In males, stimulates
spermatogenesis.
: In females, promotes
maturation of follicle and
ovulation.
: In males, stimulates
interstitial cells.
Anterior Lobe (Adenohypophysis)

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Hormones Function
• Oxytocin
• Anti Diuretic Hormone
: Promotes contraction of
uterine muscle
: Promotes contraction of
myoepithelial cells of
lactating breast.
: Increases reabsorption of
water
: Contraction of smooth
muscle.
Posterior Lobe (Neurohypophysis)

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GnRH (Gonadotrophin Releasing Hormone)
• Decapeptide, made up of 10 a.a.
• Secretes two hormones: FSH/LH
• Secreted in highly pulsatile manner.
• The amplitude and the frequency at which GnRH is
produced plays an important role in determining which
hormone will be produced.
– Higher Frequency: LH is secreted
– Lower frequency: FSH is secreted.
• The half life is 3-5 mins.

19© 2012 NOVA IVI FERTILITY |
Hypothalamus
Pituitary Gland
Target Gland
Hormone Secreted
in Blood
Inhibitory Effect Stimulatory Effect
RH
TH

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HPO Axis
Hypothalamus
Pituitary Gland
Ovary
GnRH
LHFSH
Estrogen
Feedback to
Hypothalamus
for secretions
of FSH and
LH

Endocrine system

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