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Hole’s Human Anatomy
and Physiology
Twelfth Edition
Shier w Butler w Lewis
Chapter
13
Endocrine System
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1
13.1: Introduction
• The endocrine system assists the nervous system with
communication and control of the body
• The cells, tissues, and organs are called endocrine glands
• They are ductless
• They use the bloodstream
• They secrete hormones
• There are also similar glands called paracrine and
autocrine glands that are quasi-endocrine
• Other glands that secrete substances are the exocrine glands
• They have ducts
• They deliver their products directly to a specific site
2
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Thyroid
gland
Endocrine
gland
Hormone secretion
Endocrine
cell
Blood flow
(a)
Skin
Duct
Exocrine gland
(sweat gland)
Exocrine
cells
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(b)
13.2: General Characteristics
of the Endocrine System
• The endocrine and nervous systems communicate using
chemical signals
• Neurons release neurotransmitters into a synapse
affecting postsynaptic cells
• Endocrine glands release hormones into the
bloodstream to specific target cell receptors
4
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Nerve impulse
Neuron
transmits
nerve
impulse
Neurotransmitter
released into
synapse
Postsynaptic
cell responds
(a)
Glandular
cells secrete
hormone into
bloodstream
Bloodstream
Target cells
(cells with hormone
receptors) respond
to hormone
Hormones have no
effect on other cells
(b)
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Chemistry of Hormones
Chemically, hormones are either Steroid or Non-Steroid
Steroid or steroid-like hormones examples:
• Sex hormones
• Adrenal cortex hormone
Characteristics:
• Lipids
• Complex rings of carbon and hydrogen atoms
• Insoluble in water
• Soluble in lipid cell membranes
• Easily diffused into cells
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Chemistry of Hormones
Non-steroid hormones such as:
• Amines
• Proteins
• Peptides
• Glycoproteins
Characteristics:
• Composed of long chains of amino acids
• Secreted by parathyroid and anterior/posterior
pituitary gland
• Synthesized in the adrenal medulla
8
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CH2OH
C
H3C
HO
O
OH
OH H
H3C
HO
C
C
HO
H
H
NH2
O
(a) Cortisol
(b) Norepinephrine
Val
Ala
Ser
Glu
Glu
Phe
Ile
Gly
Asp
Lys
His
His
Ser
Leu
Leu
Met
Glu
Gly
Ser
Asp
Leu
Glu
Glu
Lys
Lys
Lys
Ala
Ala
Pro
Pro
Glu
Glu
Lys
Val
Asp
His
Lys
Lys
Ser
Arg
Gly
Arg
Arg
Asp
Ser
Glu
Pro
Arg
Asp
Ala
Val
Ala
Val
Leu
Glu
Lys
Tyr
Asp
Leu
Leu
Leu
Ile
Val
Val
Asp
Ser
Lys
Lys
Gly
Try
His
Ileu
Met
Glu
Ser
Phe
Ala
Val
Leu
Glu
Lys
Gly
Glu
Arg
(c) Parathyroid ho rm one (PTH)
O
Tyr
Ile
C
Cys
Cys
H
H
H
H
C
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
O
H
H
Pro
Leu
C
OH
C
C
C
C
C
C
C
C
H H
OH
H
OH H
H
H
H
H
C
Gly
C
H
(d) Oxytocin
H
C
S
Asp
H
H
S
Glu
H
(e) Prostaglandin PGE2
H
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10
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13.3: Hormone Action
• Hormones are released into the extracellular spaces
surrounding endocrine cells
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Hypothalamus
Pituitary gland
Parathyroid gland
Pineal gland
Thyroid gland
Thymus
Adrenal gland
Kidney
Pancreas
Ovary
(in female)
Testis
(in male)
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Action of Hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Steroid Hormones
Hormone molecule
Cell
membrane
1
Newly forming
protein molecule
Ribosome
mRNA
5
Nucleus
4
mRNA
2
DNA 3
Intracellular
receptor molecule
Hormone-receptor
complex
13
Action of Hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Non-steroid Hormones
Cell membrane
2
Hormonereceptor
complex
G protein
Adenylate
cyclase
3
4
Protein
kinases
(inactive)
Nonsteroid
hormone
1 molecule
Membrane-bound
receptor molecule
ATP
cAMP
5
Substrate
(inactive)
Protein
kinases
(active)
Cytoplasm
Substrate
(active)
Nucleus
Cellular
changes
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13.1 Clinical Application
Using Hormones to Improve
Athletic Performance
15
Prostaglandins
• Prostaglandins:
• Are paracrine substances
• Are very potent in small amounts
• Are not stored in cells but synthesized just before release
• Rapidly inactivate
• Regulate cellular responses to hormones
• Can activate or inhibit adenylate cyclase
• Controls cAMP production
• Alters a cells response to hormones
• Has a wide variety of effects
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13.4: Control of
Hormonal Secretions
• Primarily controlled by negative feedback mechanism
• Hormones can be short-lived or may last for days
• Hormone secretions are precisely regulated
17
Control Sources
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Control center
Endocrine gland
inhibited.
Receptors
Hormone control
mechanism senses
change.
Effectors
Hormone secretion
decreased.
Stimulus
Hormone levels rise or
controlled process
increases.
Response
Hormone levels
return toward
normal.
too high
Normal
hormone
levels
too low
Stimulus
Hormone levels drop or
controlled process
decreases.
Receptors
Hormone control
mechanism senses
change.
Response
Hormone levels
return toward
normal.
Effectors
Hormone secretion
increased.
Control center
Endocrine gland
stimulated.
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Control Sources
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–
–
Hypothalamus
–
Nervous system
Changing level
of substance
in plasma
– Anterior pituitary gland
(a)
Peripheral
endocrine
gland
Endocrine
gland
Endocrine
gland
Target cells
Target cells
Target cells
Action
Action
Action
(b)
(c)
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13.5: Pituitary Gland
• Lies at the base of the brain in the sella turcica
• Consists of two distinct portions:
• Anterior pituitary (adenohypophysis)
• Posterior pituitary (neurohypophysis)
20
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Third ventricle
Hypothalamus
Anterior cerebral
artery
Optic chiasma
Optic nerve
Oculomotor
nerve
Pituitary stalk
(Infundibulum)
Trochlear nerve
Anterior lobe
of pituitary gland
Posterior lobe
of pituitary
gland
Sella turcica
Sphenoidal
sinus
Sphenoid bone
Basilar artery
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Anterior Pituitary Hormones
• Hypothalamic releasing hormones stimulate cells of anterior
pituitary to release hormones
• Nerve impulses from hypothalamus stimulate nerve endings
in the posterior pituitary gland to release hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Third ventricle
Optic chiasma
Neurosecretory
cells that secrete
releasing hormones
Neurosecretory cells
that secrete posterior
pituitary hormones
Hypothalamus
Hypophyseal
portal veins
Secretory cells
of anterior
pituitary gland
Capillary bed
Superior hypophyseal
artery
Capillary bed
Inferior hypophyseal
artery
Hypophyseal veins
Sella turcica of
sphenoid bone
Anterior lobe of pituitary gland
Posterior lobe of pituitary gland
22
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
–
Hypothalamus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
–
Releasing
hormone
(Hormone 1)
Secretory
cells
+
–
Anterior pituitary
Anterior pituitary
hormone
(Hormone 2)
+
Peripheral endocrine gland
© Michael Ross/Photo Researchers, Inc.
(Hormone 3)
Stimulation
+
Target cells
Inhibition
23
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Hormones from Hypothalamus
GHRH
SS
Growth
Somatostatin
hormonereleasing
hormone
PRF
Prolactinreleasing
factor
PIH
Prolactinrelease
inhibiting
hormone
TRH
Thyrotropinreleasing
hormone
CRH
Corticotropinreleasing
hormone
GnRH
Gonadotropinreleasing
hormone
Hormones from Anterior Pituitary
GH
Growth
hormone
Bone
Muscle Adipose
tissue
PRL
Prolactin
Mammary gland
TSH
Thyroidstimulating
hormone
Thyroid
ACTH
Adrenocorticotropic
hormone
Adrenal
cortex
LH
Luteinizing
hormone
Ovary
FSH
Folliclestimulating
hormone
Testis
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13.2 Clinical Application
Growth Hormone Ups and Downs
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Posterior Pituitary Hormones
• Structurally consists of nerve fibers and neuroglia v.
glandular epithelial cells of the anterior pituitary gland
• The nerve fibers originate in the hypothalamus
• Two hormones are produced:
• Antidiuretic hormone (vasopressin)
• Oxytocin
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13.6: Thyroid Gland
• The thyroid gland has two lateral lobes and lies just below
the larynx
• It produces three hormones:
• T3 (thyroxine)
• T4 (triiodothyronine)
• Calcitonin
28
Structure of the Gland
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Larynx
Colloid
Thyroid
gland
Follicular
cell
Follicular cells
Colloid
Isthmus
Extrafollicular
cell
(a)
(b)
Extrafollicular
cells
© Fred Hossler/Visuals Unlimited
29
Thyroid Hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
OH
I
OH
I
I
O
I
O
I
CH2
I
I
CH2
NH2CHCOOH
NH2CHCOOH
Thyroxine (T4)
Triiodothyronine (T3)
30
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Mediscan/Visuals Unlimited
© Mediscan/Visuals Unlimited
© Mediscan/Visuals Unlimited
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13.7: Parathyroid Glands
• The parathyroid glands are on the posterior surface of the
thyroid gland
• There are typically four parathyroid glands
• It secretes one hormone:
• PTH (parathyroid hormone or parathormone)
32
Structure of the Glands
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pharynx
Secretory cells
Thyroid
gland
Capillaries
Parathyroid
glands
© R. Calentine/Visuals Unlimited
Esophagus
Trachea
Posterior view
33
Parathyroid Hormone
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Foods
Cholesterol
Intestinal enzymes
Provitamin D
Ultraviolet light in skin
Vitamin D
(Cholecalciferol)
Also obtained directly
from foods
Liver
Hydroxycholecalciferol
Kidney
Stimulated by PTH
Dihydroxycholecalciferol
(active form of vitamin D)
Controls absorption of
calcium in intestine
Ca+2
34
Ca+2
Ca+2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parathyroid glands (on
posterior of thyroid gland)
Release into
bloodstream
Decreased blood calcium
stimulates parathyroid
hormone secretion
Stimulation
–
Increased blood
calcium inhibits
PTH secretion
Inhibition
PTH
Bloodstream
PTH
Ca+2
+
Bone
releases Ca+2
PTH
+
Ca+2
Kidneys
conserve Ca+2 and
activate Vitamin D
Ca+2
Intestine
absorbs Ca+2
Active
Vitamin D
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13.8: Adrenal Glands
• The adrenal glands are closely associated with the kidneys
• The gland sits like a cap on each kidney
• Hormones are secreted from two different areas of the
gland, the adrenal cortex and the adrenal medulla
• Numerous hormones are secreted by the adrenal glands
37
Structure of the Glands
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Surface of
adrenal gland
Capsule
Zona
glomerulosa
Connective
tissue capsule
Adrenal gland
Zona
lomerulosa
Kidney
Cortex
Zona
fasciculata
Adrenal
cortex
Adrenal cortex
Adrenal
medulla
Medulla
Zona
reticularis
Zona
fasciculata
Zona
reticularis
(a)
(b)
Adrenal
medulla
Chromaffin
cells
© Ed Reschke
38
Hormones of the Adrenal Medulla
39
Hormones of the Adrenal Cortex
40
13.3 Clinical Application
Disorders of the Adrenal Cortex
41
13.1 From Science to Technology
Treating Diabetes
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13.9: Pancreas
• The pancreas has two major types of secretory tissue
• This is why it is a dual functioning organ as both an
exocrine gland and endocrine gland
• Three hormones are secreted from the islet cells:
• Alpha cells secrete glucagon
• Beta cells insulin
• Delta cells secrete somatostatin
43
Structure of the Gland
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Pancreatic islet (Islet of Langerhans)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Gallbladder
Common bile duct
Pancreatic duct
Duct
Pancreas
Small
intestine
Digestive enzymesecreting cells
Pancreatic islet
(Islet of Langerhans)
Capillary
Hormone-secreting
islet cells
From Kent M. Van De Graaff and Stuart Ira Fox, Concepts of Human Anatomy and
Physiology, 2nd ed. ©1989 Wm. C. Brown Publishers, Dubuque, Iowa. All Rights
Reserved. Reprinted with permission
44
Hormones of the Pancreatic Islets
45
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control center
Beta cells secrete
insulin
Receptors
Beta cells detect a rise
in blood glucose
Stimulus
Rise in blood glucose
Effectors
Insulin
• Promotes movement of glucose
into certain cells
• Stimulates formation of glycogen
from glucose
Response
Blood glucose drops toward
normal (and inhibits insulin
secretion)
too high
Normal
blood glucose
concentration
too low
Stimulus
Drop in blood glucose
Receptors
Alpha cells detect a drop
in blood glucose
Response
Blood glucose rises toward
normal (and inhibits glucagon
secretion)
Effectors
Glucagon
• Stimulates cells to break down glycogen
into glucose
• Stimulates cells to convert
noncarbohydrates into glucose
Control center
Alpha cells secrete
glucagon
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13.4 Clinical Application
Diabetes Mellitus
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13.10: Other Endocrine Glands
Pineal Gland
• Secretes melatonin
• Regulates circadian rhythms
Thymus Gland
• Secretes thymosins
• Promotes development of certain lymphocytes
• Important in role of immunity
Reproductive Organs
• Ovaries produce estrogens and progesterone
• Testes produce testosterone
• Placenta produces estrogens, progesterone, and
gonadotropin
Other organs: digestive glands, heart, and kidney
48
13.11: Stress and Its Effects
• Survival depends on maintaining homeostasis
• Factors that change the internal environment are
potentially life-threatening
• Sensing such dangers directs nerve impulses to the
hypothalamus
• This can trigger a loss of homeostasis
49
Types of Stress
• Two types of stress:
• Physical stress
• Psychological stress
50
Responses to Stress
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Stress results from changes
in the external environment
Hormonal signals
Neural signals
Signals from
sensory receptors
Sympathetic impulses
Hypothalamus
Adrenal medulla
Epinephrine and
norepinephrine
released
CRH released
Anterior pituitary
Norepinephrine
released
Short-term “fight or flight” or alarm stage.
• Blood glucose increases.
• Blood glycerol and fatty acids increase.
• Heart rate increases.
• Blood pressure rises.
• Breathing rate increases.
• Air passages dilate.
• Pupils dilate.
• Blood flow redistributes.
ACTH released
Adrenal cortex
Cortisol released
Long-term adjustment or resistance stage
• Increase in blood concentration of amino acids.
• Increased release of fatty acids.
• Increased glucose formed from
noncarbohydrates—amino acids (from
proteins) and glycerol (from fats).
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13.12: Lifespan Changes
• Endocrine glands decrease in size
• Muscular strength decreases as GH levels decrease
• ADH levels increase due to slower break down in liver
and kidneys
• Calcitonin levels decrease; increase risk of osteoporosis
• PTH level changes contribute to risk of osteoporosis
• Insulin resistance may develop
• Changes in melatonin secretion affect the body clock
• Thymosin production declines increasing risk of infections
53
Important Points in Chapter 13:
Outcomes to be Assessed
13.1: Introduction
 Define hormone.
 Distinguish between endocrine and exocrine glands.
13.2: General Characteristics of the Endocrine System
 Explain what makes a cell a target cell for a hormone.
 List some important functions of hormones.
13.3: Hormone Action
 Describe how hormones can be classified according to their chemical
composition.
 Explain how steroid and non-steroid hormones affect their target cells.
54
Important Points in Chapter 13:
Outcomes to be Assessed
13.4: Control of Hormone Secretion
 Discuss how negative feedback mechanisms regulate hormone
secretion.
 Explain how the nervous system controls hormone secretion.
13.5-13.10: Pituitary Gland – Other Endocrine Glands
 Name and describe the locations of the major endocrine glands and
list the hormones that they secrete.
 Describe the actions of the various hormones and their contributions
to homeostasis.
 Explain how the secretion of each hormone is regulated.
55
Important Points in Chapter 13:
Outcomes to be Assessed
13.11: Stress and Its Effects
 Distinguish between physical and psychological stress.
 Describe the general stress response.
13.12: Lifespan Changes
 Describe some of the changes associated with aging of the endocrine
system.
56
Quiz 13
Complete Quiz 13 now!
Read Chapter 14.
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