Chapter 14
Endocrine System
Human Anatomy
Sixth Edition
Kent M. Van De Graaff
(c) The McGraw-Hill Companies, Inc.
The Endocrine System
Chapter Concepts
1. Glands can be classified structurally and functionally
as endocrine or exocrine.
2. Both the nervous and endocrine systems work together
through different modes of action to regulate body
activities and maintain homeostasis.
3. Hormones are transported by the blood to target cells
where they are responsible for specific functions.
4. Elaborate feedback mechanisms ensure homeostasis
within the body systems.
5. Alterations in hormonal balance may result in serious
clinical manifestations.
It’s All About the Anatomy
And maybe a little chemistry ……
Groups of three or four
Books closed and whatdaya know?
The Endocrine System
Objectives for Today
1. Distinguish between endocrine and exocrine
glands
2. Compare and contrast the nervous and
endocrine systems with regard to body
regulation and homeostasis
3. Define mixed gland and identify them
4. Describe the action of a hormone on its target
5. Differentiate between the three principle kinds
of hormones
Endocrine versus Exocrine Glands
In groups, compare the diagrams on
the next slide using the similarities
and differences routine.
How can endocrine glands be
distinguished from exocrine glands?
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Endocrine versus Exocrine Glands
Exocrine
Produce secretions transported through
ducts to destination
Endocrine
• Ductless
• Secrete specific chemicals (hormones)
into circulation
• Target cells
Endocrine versus Nervous System
Endocrine System
Secretes hormones

Travel through
bloodstream
Action relatively slow
Effects are prolonged
Nervous System
Electrochemical
impulses via neurons
Rapid response
Effects are brief
Two systems are closely coordinated in
autonomically controlling the functions of the
body.
Glands of the Endocrine System
Distributed throughout the body
Introductory Video
Endocrine Organs
Cranial Cavity
Neck
Abdomen
Mixed Glands
Have exocrine as
well as endocrine
functions
Glands of the Endocrine System
QUIZ TIME!
Glands of the Endocrine System
Distributed throughout the body
Cranial cavity: pituitary gland,
hypothalamus, pineal gland
Neck: thyroid and parathyroid glands
Abdomen: adrenal glands and pancreas
Pelvic cavity: gonads of the female
Scrotum: gonads of the male
Other Endocrine Tissues
Several of the "other" endocrine cells and
tissues are sometimes referred to as the
diffuse endocrine system
Many organs house clusters of cells that
secrete hormones.
The kidney, for example, contains scattered
cells that secrete erythropoietin, a hormone
essential for production of red blood cells.
Even the heart contains cells that produce
atrial naturetic hormone, which is important
in sodium and water balance.
Hormones
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Act as chemical
messengers
Three basic kinds:



Proteins
Steroids
Amines
Derived from amino
acids or cholesterol
Steroid Hormones
Soluble in lipids
Pass through cell
membrane
Steroid-protein
complex stimulates
gene expression

Steroid hormone
response
Hormones (Intracellular Receptors)
Despite the molecular diversity of hormones, all hormone
receptors can be categorized into one of two types, based on
their location within the cell:
Location of Receptor: Intracellular receptors – cytoplasm
and/or nucleus
Classes of Hormones: Steroids and Thyroid Hormones
Principle Mechanism of Action: Alter transcriptional
activity of responsive genes
Protein and Amine Hormones
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Insoluble in lipids
Requires receptors on
cell membrane



Receptor binding
increases adenylate
cyclase activity
ATP converted to
cyclic AMP
Stimulates change in
cellular processes
Hormones (Cell surface receptors)
Despite the molecular diversity of hormones, all hormone
receptors can be categorized into one of two types, based on
their location within the cell:
Location of Receptor: Cell surface receptors (plasma
membrane)
Classes of Hormones: Proteins and Amines
Principle Mechanism of Action: Generation of second
messengers which alter the activity of other molecules usually enzymes - within the cell
Control of Hormone Secretion
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Negative Feedback
Maintains status quo
Gland continues to
secrete until target
cells provide message
to stop
Message is generally
in form of a second
hormone
Signals endocrine
organ to stop
Control of Hormone Secretion (2)
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Neural Impulses
Autonomic
nervous system
Causes endocrine
gland to secrete
(e.g. adrenal gland)
Mind/body connection
Hypothalamus secretes releasing factors
Stimulates cells of pituitary to secrete hormones
The Pituitary Gland
Objectives
7. Describe the actions of anterior
pituitary hormones
8. Explain how secretions from the
anterior and posterior pituitary are
controlled by the hypothalamus
9. Explain how the secretion of anterior
pituitary hormones is regulated by
negative feedback
Pituitary Gland - Anatomy
Region of the diencephalon
Attached to brain by pituitary stalk
 Contains
infundibulum
Adenohypophysis (Anterior lobe)
 Secrete
hormones
 Neural control by hypothalamus
 Negative feedback control
Neurohypophysis (Posterior lobe)
 Releases
hormones produced by
hypothalamus
The Pituitary Gland
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Pituitary Gland Structure
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Adenohypophysis
Pars distalis
(anterior pituitary)
Pars tuberalis
Neurohypophysis
Lobus nervosa
Infundibulum

Connects to
hypothalamus
Posterior Pituitary
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Stores and releases
hormones produced
by hypothalamus
Specialized neurons
Hormones transported along axons in the
hypothalamo-hypophyseal tract (within
infundibulum)
Anterior Pituitary – Hormones (1)
Growth Hormone (GH)
Stimulates cell
growth
Stimulates mitosis
Regulated by the
hypothalamus
Thyroid Stimulating
Hormone (TSH)
Regulates thyroid
gland
Adrenocorticotropic
hormone (ACTH)
Promotes normal
function of adrenal
cortex
Breakdown fats
Anterior Pituitary – Hormones (2)
Luteinizing hormone
(LH)
Onsets ovulation
Stimulates corpus
luteum
Stimulates release of
progesterone
Follicle Stimulating
Hormone (FSH)
Regulates
development of follicle
Stimulates release of
estrogen
GONADOTROPHINS
Anterior Pituitary – Hormones (3)
Prolactin
Assists with milk
production
Melanocyte Stimulating
Hormone (MSH)
Darkens skin
Endocrine functions
unclear
Anterior Pituitary - Summary
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Posterior Pituitary – Hormones
Oxytocin
Influences activity of
female reproductive
system
Released at end of
gestation
Causes uterine
contractions
Milk ejection reflex
during lactation
Antidiuretic Hormone
(ADH)
Inhibits formation of
urine
Reduces water
excretion
Hypothalamo-hypophyseal Portal System
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Hypothalamus
Hormones
Median
Eminence
Primary Capillaries
Pituitary Stalk
Secondary Capillaries
Pars Distalis
Thyroid and Parathyroid Gland
Objectives
10. Describe the location and structure of
the thyroid gland and list the actions
of thyroid hormones
11. Describe the location and structure of
the parathyroid gland and list the
actions of parathyroid hormone
Regulated by hypothalamus
Regulated by TSH
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In the neck
Below larynx
Two lobes
Separated by isthmus
Thyroid Gland Function
Thyroxin (T4)




Triiodothyronin (T3)
Release is controlled by hypothalamus (TSH)
Regulate metabolic rate
Increase protein synthesis
Iodine essential for hormone production
Calcitonin




Regulates calcium levels in blood
Decreases breakdown of bone
Stimulates excretion of Ca++ at kidney
Decreases blood Ca++ levels
Goiter Formation
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Lack of iodine
Interferes with
negative feedback
control of TSH
Results in abnormal
enlargement of the
thyroid gland
Parathyroid Gland
Embedded in posterior
surface of thyroid gland
Usually four glands
(superior and inferior pair)
Parathyroid hormone (PTH)
Increases blood Ca++ levels
Acts on bone, kidney, small
intestine
Actions of Parathyroid Hormone
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Opposes effects of
calcitonin
Increase in PTH
causes



Bones to release
calcium
Kidneys to conserve
calcium
Small intestine to
absorb calcium
Negative feedback
control
Pancreas
Objectives
12. Describe the structure of the
endocrine portion of the pancreas and
the origin of insulin and glucagon
13. Describe the actions of insulin and
glucagon
Pancreas
Mixed gland
Endocrine portion:
Pancreatic Islets
2 cell types:
Alpha – glucagon
Beta – insulin
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Endocrine Function of the Pancreas
Glucagon



Stimulates liver
Glycogen to glucose
Increase blood glucose
Insulin




Decrease blood glucose
Promotes muscle/adipose cells to take up
glucose
Stimulates glucose to glycogen in muscle/liver
Failure of beta cells = diabetes mellitus
Adrenal Gland
Objectives
14. Describe the location of the adrenal
glands and distinguish between the
adrenal cortex and the adrenal
medulla
15. List the hormones secreted by the
adrenal glands and discuss their
effects
Adrenal Gland
Paired organ
Superior border of
kidney
Adrenal Medulla



Chromaffin cells
Sympathetic
innervation
Catecholamines
Adrenal Cortex


Bulk of gland
Corticosteroids
Adrenal Gland Function
Adrenal Cortex
Mineralocorticoids




Regulate electrolytes
Aldosterone
Increase water retention
Decrease urine output
Glucocorticoids



Carbohydrate, protein, fat
metabolism
Anti-inflammatory
Regulated by ACTH
Gonadocorticoids

Supplement sex hormones
Adrenal Medulla
Epinephrine and
norepinephrine
Effects similar to ANS
except hormonal effects
are 10 times longer
lasting
Prepares body for
greater activity
Stress
Physiological
change in the
body
Elicited by neural
impulses from
hypothalamus
Adrenal medulla
releases
epinephrine
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Other Endocrine Glands
Objectives
16. Discuss the endocrine functions of
the gonads
17. Describe the structure and location of
the pineal and thymus glands and
their endocrine functions
Gonads
Testes
Ovaries
Mixed gland
Produce estrogen
 Development of secondary
Interstitial cells
sex organs
produce testosterone
 Menstrual changes
Development of
 Promotes secondary sex
secondary sex organs
characteristics
Promotes secondary
Produce progesterone
sex characteristics


Associated with pregnancy
Prepare uterus for
implantation
Pineal Gland
Small cone-shaped organ
Roof of third ventricle
Innervated by the sympathetic NS
Secretes melatonin
Rhythmic daily release (circadian)
Thought to affect hypothalamus
Thymus
Upper mediastinum
Front of aorta
Associated with
lymphatic system
Thymosin
Stimulates T-cell
production
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The End.