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The Endocrine
System
© 2009 The McGraw-Hill Companies, Inc. All rights reserved
Introduction

The endocrine system includes the organs of the
body that secrete hormones directly into body fluids
such as blood

Regulates chemical reaction in cells and therefore control
functions of the organs, tissues, and other cells
bloodstream
to
Glands
into
secrete
hormones
target tissues
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34-3
Hormones

Endocrine glands


Ductless
Release hormones



Directly into target tissues
Into bloodstream to be carried to target tissues
Hormones – chemicals secreted by a cell that
affect the functions of other cells
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34-4
Hormones (cont.)


Many are derived from steroids that easily
cross the cell membrane
Examples of steroid hormones




Estrogen
Progesterone
Testosterone
Cortisol
hormones
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34-5
Hypothalamus

Hormones


Oxytocin
Antidiuretic hormone (ADH)

Hormones transported to the posterior
pituitary for storage

Directs posterior pituitary to release hormones
Glands
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Pituitary Gland



Controlled by the hypothalamus
Located at the base of the brain
Two lobes
 Anterior lobe
 Posterior lobe
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Pituitary Gland (cont.)
Growth hormone
Stimulates increase in size
of muscles and bones
Luteinizing
Prolactin Stimulates milk
production
Anterior
Lobe
Females: stimulates ovulation
and estrogen production
Males: stimulates testosterone production
Adrenocorticotropic
Stimulates the adrenal cortex
to release its hormones
Thyroid-stimulating
Stimulates the thyroid
gland to release its
hormones
Follicle-stimulating
Females: stimulates estrogen
production and maturation of the ova
Males: stimulates sperm production
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Pituitary Gland (cont.)
Oxytocin
Posterior
Lobe
Antidiuretic hormone (ADH)
Stimulates the kidneys to
conserve water
Females: causes
contraction of the
uterus and ejection of
breast milk
Males: stimulates
contraction of the
prostate and vas
deferens during
sexual arousal
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Thyroid Gland and
Parathyroid Glands
Thyroid Gland
Located below the larynx
 Divided into follicles that store some of the hormones

Major hormones
T3 T4
Stimulate protein synthesis and
increase cellular energy
production
Lowers blood calcium levels
by activating osteoblasts that
Glands
build new bone tissue
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Thyroid Gland and
Parathyroid Glands (cont.)

Parathyroid glands

Four located on the posterior surface of the
thyroid gland

Secrete parathyroid hormone (PTH)

Agonist to calcitonin by raising blood calcium levels
through activation of osetoclasts (dissolve bone)

As bone dissolves, calcium levels in blood increase
Glands
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Adrenal Glands



Located on top of each kidney
Divided into the adrenal medulla and adrenal cortex
Adrenal medulla


Central portion
Hormones
 Epinephrine
 Norepinephrine
 Same effects as sympathetic nervous system
Glands
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Adrenal Glands (cont.)

Adrenal cortex


Outermost portion
Secretes many hormones, but main ones are

Aldosterone



Stimulates body to retain sodium and water
Important in maintaining BP
Cortisol



Released when stressed
Decreases protein synthesis, resulting in slowed tissue repair
Decreases inflammation
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Pancreas


Located behind the
stomach
Both exocrine gland and
endocrine gland


Exocrine – secretes
digestive enzymes into a
duct leading to the small
intestine
Endocrine – secretes
hormones into
bloodstream
Glands
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Pancreas (cont.)

Islets of Langerhans secrete hormones into
bloodstream


Alpha cells secrete glucagon
Beta cells secrete insulin
Blood glucose
concentrations
Protein synthesis
Blood glucose
concentrations
Protein synthesis
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Other Hormone-Producing Organs

Pineal body



Small gland
Located between
cerebral hemispheres
Melatonin


Regulates circadian
rhythms
May play a role in
onset of puberty

Thymus gland


Located between
lungs
Thymosin

Promotes
production of
T lymphocytes
Glands
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Other Hormone-Producing
Organs (cont.)

The gonads

Ovaries






Gastrin

Secretin
Cholecystokinin
Heart

Testosterone
Stomach
Small intestine

Estrogen
Progesterone
Testes



Atrial natriuretic
peptide – regulates BP
Kidneys

Erythropoietin –
stimulates blood cell
production
Glands
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34-17
Back
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Common Diseases and Disorders
Disease/Disorder
Acromegaly
Description
Too much growth hormone produced in adults;
enlargement of bones and thickened skin
Addison’s disease Adrenal gland fails to produce enough
corticosteroids
Cretinism
Extreme form of hypothyroidism present prior
to or soon after birth
Cushing’s disease Hypercortisolism; over-production of cortisol
Diabetes insipidus Kidneys fail to reabsorb water, resulting in
excessive urination; hyposecretion of ADH
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Common Diseases and Disorders (cont.)
Disease/Disorder
Diabetes mellitus
Description
Chronic disease characterized by elevated
blood glucose levels
Type I
Insulin-dependent diabetes mellitus; usually develops
in childhood
Noninsulin-dependent diabetes mellitus; primarily in
adults but increased incidence in teens
Occurs during pregnancy; usually temporary
Type II
Gestational
Dwarfism
Too little growth hormone (somatotropin)
produced during childhood
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Common Diseases and Disorders (cont.)
Disease/Disorder Description
Gigantism
Too much growth hormone produced during
childhood
Goiter
Enlargement of thyroid gland, causing
swelling in neck; deficiency of iodine in diet
Grave’s disease
Hyperthyroidism; antibodies attach to thyroid
gland, causing it to produce too much thyroid
hormone
Myxedema
Thyroid gland produces inadequate amounts of
thyroid hormone; common in females over 50
© 2009 The McGraw-Hill Companies, Inc. All rights reserved