3. 39-1 The Endocrine System
The endocrine system is made up of
glands that release their products
into the bloodstream.
These products deliver messages throughout
the body.
The chemicals released by the endocrine
system can affect almost every cell in the
body.
4. Hormones
Hormones are chemicals released in
one part of the body that travel
through the bloodstream and affect
the activities of cells in other parts of
the body.
5. Hormones bind to specific chemical receptors on
cells.
Cells that have receptors for a particular hormone
are called target cells.
If a cell does not have receptors or the receptors
do not respond to a hormone, that hormone has
no effect on it.
6. A gland is an organ that produces and releases
a secretion. There are two kinds of glands:
Exocrine glands release secretions
through ducts directly to the organs
that use them.
Endocrine glands release their
secretions directly into the
bloodstream.
7. Hypothalamus
The hypothalamus makes
hormones that control the
pituitary gland. In
addition, the
hypothalamus makes
hormones that are stored
in the pituitary gland.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
8. Pituitary gland
The pituitary gland
produces hormones
that regulate many of
the other endocrine
glands.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
9. Parathyroid glands
The parathyroid glands
release parathyroid
hormone, which regulates
the level of calcium in the
blood.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
10. Thymus
During childhood, the
thymus releases
thymosin, which
stimulates T cell
development and proper
immune response.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
11. Adrenal glands
The adrenal glands
release epinephrine and
norepinephrine, which
help the body respond
to stress.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
12. Testis
The testes produce
testosterone, which is
responsible for sperm
production and the
development of male
secondary sex
characteristics.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
13. Ovary
Ovaries produce estrogen
and progesterone.
Estrogen is required for
the development of
female secondary sex
characteristics and for
the development of eggs.
Progesterone prepares
the uterus for a fertilized
egg.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
14. Pancreas
The pancreas produces
insulin and glucagon,
which regulate the level
of glucose in the blood.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
15. Thyroid
The thyroid produces
thyroxine, which
regulates metabolism
throughout the body.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
16. Pineal gland
The pineal gland releases
melatonin, which is
involved in rhythmic
activities, such as daily
sleep-wake cycles.
Figure 39-2 on Page 998
Know the endocrine
glands and their functions.
17. Hormone Action
Hormones are classified as either
steroids or nonsteroids.
Steroid hormones are produced
from a lipid called cholesterol.
Nonsteroid hormones include proteins,
small peptides, and modified amino acids.
25. A nonsteroid
hormone binds to
receptors on the
cell membrane.
This activates an
enzyme on the
inside of the
membrane.
Nonsteroid hormone
(first messenger)
26. This enzyme
activates
secondary
messengers that
carry the message
of the hormone
inside the cell.
These messengers
activate and inhibit
many cell activities.
ATP cAMP
(second messenger)
Enzyme
activities
Altered
cellular
function
27. Prostaglandins
All cells (except red blood cells) produce
small amounts of hormone-like
substances called prostaglandins.
Prostaglandins are modified fatty acids.
They affect nearby cells and tissues, and
are known as “local hormones.”
28. The endocrine system is regulated by
feedback mechanisms that function to
maintain homeostasis.
In feedback inhibition, an
increase in a substance
causes a decrease in the
production of the substance.
30. Complementary Hormone Action
Sometimes two hormones with
opposite effects act to regulate
part of the body’s internal
environment.
Such a complementary system regulates
the level of calcium ions in the
bloodstream.
31. Two hormones that regulate calcium
concentration are calcitonin and parathyroid
hormone (PTH).
Calcitonin decreases the level of calcium in the
blood, while PTH increases it.
33. 39-2 Human Endocrine Glands
The endocrine glands are scattered throughout
the body.
The human endocrine system regulates a variety
of activities.
Any improper functioning of an endocrine gland
may result in a disease or a disorder.
34. The major glands of the endocrine system
include:
• the pituitary gland
• the hypothalamus
• the thyroid gland
• the parathyroid glands
• the adrenal glands
• the pancreas
• the reproductive glands
35. The pituitary gland secretes nine
hormones that directly regulate
many body functions and controls
the actions of several other
endocrine glands.
42. The close connection between the hypothalamus
and the pituitary gland means that the
nervous and endocrine systems
act together to coordinate body
activities.
43. The thyroid gland is located at the base of
the neck and wraps around the upper part
of the trachea.
The thyroid gland has the major
role in regulating the body's
metabolism.
44. The thyroid produces thyroxine.
Thyroxine regulates the metabolic rate of cells.
46. Thyroid Disorders
Hyperthyroidism: the body produces too much
thyroxine. It is characterized by elevated
temperature and metabolic rate, increased blood
pressure, and weight loss.
Hypothyroidism: the body produces too little
thyroxine. It is characterized by lower temperature
and metabolic rate, lack of energy, and weight
gain.
Goiter: enlargement of thyroid gland. Caused by
an iodine deficiency.
47. The four parathyroid glands are found on
the back surface of the thyroid gland.
Hormones from the parathyroid
glands act to maintain
homeostasis of calcium levels in
the blood.
49. The adrenal glands are two pyramid-
shaped structures that sit on top of the
kidneys, one gland on each kidney.
The adrenal glands release
hormones that help the body
prepare for and deal with stress.
51. Epinephrine and norepinephrine:
•increase heart rate, blood pressure, and
blood flow to the muscles.
•cause air passageways to open wider,
allowing for an increased intake of
oxygen.
•stimulate the release of extra glucose
into the blood to help produce a sudden
burst of energy.
52. The pancreas has both exocrine
and endocrine functions.
•It is a digestive gland whose
secretions break down food.
•It produces insulin and glucagon.
54. Insulin stimulates cells in the liver and muscles to
remove sugar from the blood and store it as
glycogen or fat.
Glucagon stimulates the liver to break down
glycogen and release glucose back into the blood.
57. The gonads are the body’s reproductive
glands.
The gonads serve two important
functions: the production of
gametes, and the secretion of
sex hormones.
58. The female gonads—the ovaries—
produce eggs.
The male gonads—the testes—
produce sperm.
The gonads also produce sex
hormones.
59. The ovaries produce the female sex hormones
estrogen and progesterone.
Progesterone prepares the uterus for the arrival of
a developing embryo.
Estrogen is needed for the development of eggs
and for the formation of physical characteristics
of the female body.
60. The testes produce testosterone, which is needed
for normal sperm production and development of
male physical characteristics.
62. Sexual Development
•In humans, the reproductive system
produces, stores, and releases specialized
sex cells known as gametes.
•Sperm + egg = zygote, the single
cell from which all cells of the
human body develop.
63. •Puberty is a period of rapid growth and
sexual maturation during which the
reproductive system becomes fully
functional.
•When puberty ends, reproductive
organs are fully developed.
•Puberty usually begins between the ages of
9 and 15, and usually starts one year earlier
in females than in males.
64. Puberty begins when the hypothalamus signals
the pituitary to produce increased levels of two
hormones that affect the gonads.
These hormones are follicle-stimulating hormone
(FSH) and luteinizing hormone (LH).
65. The main function of the male
reproductive system is to produce and
deliver sperm.
66. A sperm cell consists of:
• a head, which
contains the
nucleus
• a midpiece, which
contains energy-
releasing
mitochondria
• a tail, which
propels the cell
forward
Head
Nucleus
Midpiece
Mitochondria
Tail
67. Male Reproductive System
Urinary bladder
Vas deferens
Pubic bone
Urethra
Penis
Seminal vesicle
Rectum
Prostate gland
Bulbourethral
gland
Scrotum
Testis
Epididymis
68. The testes are located in an external sac called
the scrotum.
The scrotum is located outside the body cavity,
where it is between 1 and 3 degrees cooler than
normal body temperature. The lower temperature
helps sperm development.
69. Within each testis are clusters of hundreds of tiny
tubules called seminiferous tubules.
The seminiferous tubules are tightly coiled and
twisted together.
Sperm are produced in the seminiferous tubules.
70. Sperm produced in the seminiferous
tubules, within the testis, move into
the epididymis, where they mature
and are stored.
71. From there, sperm move into a tube called the vas
deferens, which extends up from the scrotum into
the abdominal cavity.
Sperm enter the vas deferens,
which merges with the urethra, the
tube that leads to the outside of the
body through
the penis.
72. Glands lining the reproductive tract produce
seminal fluid.
Seminal fluid nourishes sperm and protects them
from the acidity of the female reproductive tract.
The combination of sperm and seminal fluid is
called semen.
73. Male reproductive diagram
Seminiferous tubules- In testes,
where sperm are made (meiosis)
Epididymis- where sperm matures &
waits
Vas deferens- tube from testes
Urethra- where sperm
& urine exit
74. The Female Reproductive System
•The primary reproductive organs in the
female are the ovaries.
•The ovaries are located in the abdominal
cavity.
75. The main function of the female
reproductive system is to produce eggs.
In addition, the female reproductive system
prepares the female's body to nourish a
developing embryo.
77. Egg Development
•Each ovary contains about 400,000 primary
follicles, which are clusters of cells
surrounding a single egg.
•The follicle helps an egg mature for release
into the reproductive tract, where it can be
fertilized.
•Eggs develop
within their follicles.
78. Egg Release
•When a follicle has matured, its
egg is released from the ovary in
a process called ovulation.
•The follicle breaks open,
and the egg is swept
from the ovary into one
of the two Fallopian
tubes.
79. •While in the Fallopian tube, an
egg can be fertilized.
•After a few days, the egg passes from the
Fallopian tube into the uterus.
•If the egg is not fertilized it passes
through the cervix, and finally out of the
vagina.
•The vagina leads to the outside of the
body.
80. The Menstrual Cycle
•The menstrual cycle is controlled by
internal feedback mechanisms between
the reproductive system and the
endocrine system.
•The menstrual cycle takes an
average of 28 days.
81. During the menstrual cycle, an egg develops and
is released from an ovary.
The uterus is prepared to receive a fertilized egg.
If the egg is fertilized, it is implanted in the uterus
and embryonic development begins.
If the egg is not fertilized, it is discharged.
82. The menstrual cycle has four phases:
•follicular phase
•ovulation
•luteal phase
•menstruation
85. •The anterior pituitary secretes FSH and
LH, which cause a follicle to develop to
maturity.
•As the follicle develops, cells
surrounding the egg enlarge and produce
more estrogen.
•Estrogen causes the lining of the uterus
to thicken.
86. Ovulation
•This phase occurs midway through the
cycle and lasts 3–4 days.
•The pituitary gland produces more FSH
and LH.
•The release of these hormones causes
the follicle to rupture, and a mature egg is
released into one of the Fallopian tubes.
87. Luteal Phase
•The luteal phase begins after the egg is
released.
•The first few days of the luteal
phase is when fertilization is most
likely.
88. Luteal Phase
•As the egg moves in the Fallopian tube,
the follicle turns yellow and is called the
corpus luteum.
•The corpus luteum continues to release
estrogen but also begins to release
progesterone.
89. Progesterone stimulates growth and
development of the blood supply and
surrounding tissue.
Within a few days of implantation, the
uterus and the growing embryo will release
hormones that keep the corpus luteum
functioning for several weeks.
This allows the lining of the uterus to
nourish and protect the developing
embryo.
90. Menstruation
•If fertilization does not occur, the corpus
luteum will begin to disintegrate.
•The follicle breaks down and releases less
hormones, which makes the uterine lining
detach.
•This tissue, blood, and the unfertilized egg are
discharged through the vagina.
•This phase is menstruation, and it lasts 3–7
days.
91. Female reproductive diagram
Ovary- egg develops & is released
Fallopian tube- Fertilization
usually happens here
Uterus- Where baby develops
Vagina- birth canal
92. Sexually Transmitted Diseases
•Diseases that spread from one person to
another during sexual contact are called
sexually transmitted diseases (STDs).
•STDs are a serious problem in the U.S.,
infecting millions of people each year and
accounting for thousands of deaths.
93. STDs caused by bacteria include chlamydia,
syphilis, and gonorrhea.
STDs caused by viruses include hepatitis B,
genital herpes, genital warts, and HIV/AIDS.
95. When an egg is fertilized, human development
begins.
In this process, a single cell undergoes a series of
cell divisions that results in the formation of a
new human being.
96. Fertilization
•During sexual intercourse, sperm are
released when semen is ejaculated
through the penis into the vagina.
•Sperm swim through the uterus into the
Fallopian tubes.
•if an egg is present in one of the
Fallopian tubes, its chances of being
fertilized are good.
97. The egg is surrounded by a protective layer that
contains binding sites to which sperm can attach.
When a sperm attaches to a binding site, its head
releases enzymes that break down the protective
layer of the egg.
The sperm nucleus enters the egg, and
chromosomes from the sperm and egg are
brought together.
98. The process of a sperm joining an egg is
called fertilization.
99. Fertilization
After the two haploid (N) nuclei fuse,
a single diploid (2N) nucleus is
formed.
A diploid cell has a set of
chromosomes from each parent cell.
The fertilized egg is called a zygote.
100. Early Development
•While still in the Fallopian tube, the
zygote begins to undergo mitosis.
•Four days after fertilization, the embryo
is a solid ball of about 64 cells called a
morula.
101. The stages of early development
include implantation, gastrulation,
and neurulation.
102. Implantation
•As the morula grows, it becomes a hollow
structure with an inner cavity called a
blastocyst.
•6–7 days after fertilization, the blastocyst
attaches to the uterine wall.
•The embryo secretes enzymes that digest
a path into it.
•This process is known as implantation.
104. Blastocyst cells specialize due to the activation of
genes.
This process, called differentiation, is responsible
for the development of the various types of tissue
in the body.
105. Gastrulation
•The inner cell mass of the blastocyst
gradually sorts itself into two layers,
which then give rise to a third layer.
107. The result of gastrulation is the
formation of three cell layers—the
ectoderm, the mesoderm, and the
endoderm.
Amniotic cavity
Primitive
streak
Ectoderm
Endoderm
Mesoderm
108. The ectoderm develops into the skin and nervous
system.
The endoderm forms the digestive lining and
organs.
Mesoderm cells differentiate into internal tissues
and organs.
110. Shortly after gastrulation is complete, a block of
mesodermal tissue begins to differentiate into the
notochord.
111. Neural crest Neural fold
Notochord
•As the notochord develops, the neural
groove changes shape, producing neural
folds.
112. Neural crest Neural tube
Ectoderm
Notochord
•Gradually, these folds move together to
create a neural tube from which the
spinal cord and the nervous system
develop.
113. Extraembryonic Membranes
•As the embryo develops, membranes
form to protect and nourish the embryo.
•Two of these membranes are the amnion
and the chorion.
114. •The amnion
develops into a
fluid-filled
amniotic sac.
•The amniotic
sac cushions
and protects
the developing
embryo.
Uterus
Amnion
Fetus
Amniotic sac
Placenta
Umbilical cord
115. Fingerlike projections called chorionic villi form
on the outer surface of the chorion and extend
into the uterine lining.
Fetal portion
of placenta
Maternal portion
of placenta
Maternal
artery
Maternal
vein
Umbilical
vein
Umbilical
arteries
Umbilical cord
Amnion
Chorionic villus
Mom &
baby
blood do
NOT
mix!!
116. The chorionic villi and uterine lining form the placenta.
The placenta
•Lies between the
uterus and the
developing embryo
•provides nutrients
to the fetus.
117. The placenta is the embryo's organ of
respiration, nourishment, and excretion.
118. The placenta acts as a barrier to some harmful or
disease-causing agents.
Some disease causing agents, such as German
measles and HIV can cross the placenta.
Some drugs, including alcohol and medications
also can penetrate the placenta and affect
development.
119. After eight weeks, the embryo is called a
fetus.
After three months, most major organs and
tissues are formed. During this time, the
umbilical cord also forms.
The umbilical cord connects
the fetus to the placenta.
120. Later Development
•4–6 months after fertilization:
•The heart can be heard with a
stethoscope.
Bone replaces cartilage that forms the
early skeleton.
A layer of soft hair grows over the
fetus’s skin.
The fetus grows and the mother can
feel it moving.
121. During the last three months, the organ systems
mature.
•The fetus doubles in mass.
•It can now regulate its body
temperature.
•The central nervous system and lungs
completely develop.
122. Childbirth
•About nine months after fertilization, the
fetus is ready for birth.
•A complex set of factors affects the
onset of childbirth.
123. Multiple Births
Multiple Births
•If two eggs are released during the same
cycle and fertilized by two different
sperm, fraternal twins result.
•A single zygote may split apart to
produce two embryos, which are called
identical twins.
124. 39-1
Chemicals that travel through the
bloodstream and affect the activities of
other cells are known as
a. hormones.
b. receptors.
c. enzymes.
d. messengers.
125. 39-1
Which group of hormones act on target
cells by binding directly to DNA in the
nucleus?
a. steroids
b. nonsteroids
c. proteins
d. second messengers
126. 39-2
Diabetes mellitus is a disease that
results when the pancreas fails to
produce or properly use
a. glucose.
b. insulin.
c. glucagon.
d. carbohydrate.
128. 39-2
The gonads are the body's
a. target cells.
b. exocrine glands.
c. reproductive glands.
d. reproductive cells.
129. 39-2
The endocrine glands responsible for
maintaining homeostasis of calcium in
the blood are the
a. thyroid and parathyroid glands.
b. adrenal and pituitary glands.
c. hypothalamus and thyroid glands.
d. gonads.
130. 39-2
Epinephrine is a hormone produced by the
adrenal medulla and is responsible for
a. the “fight or flight” response to stress.
b. controlling the level of insulin in the
blood.
c. maintaining proper levels of sodium and
potassium in the blood.
d. regulating the water content of the body.
131. 39-3
The process in which a mature egg is
released from the follicle of an ovary is
known as
a. fertilization.
b. ovulation.
c. menstruation.
d. meiosis.
132. 39-3
An egg passes from a Fallopian tube
into the cavity of the
a. ovary.
b. vagina.
c. uterus.
d. cervix.
133. Which statement best describes male sperm
cells?
a. They are motile, produced in small numbers, and larger than most body
cells.
b. They are motile, produced in large numbers, and smaller than most body
cells.
c. They are nonmotile, produced in small numbers, and larger than most
body cells.
d. They are nonmotile, produced in large numbers, and smaller than most
body cells.
135. 39–4
The central nervous system develops
during which phase of early
development?
a. gastrulation
b. neurulation
c. implantation
d. fertilization
136. 39–4
The placenta is a structure that
a. belongs entirely to the mother.
b. belongs entirely to the fetus.
c. brings blood from the mother and
fetus close together.
d. provides an impermeable barrier
between the mother and the fetus.
137. 39–4
Which of the following is not a primary
germ layer?
a. neural tube
b. endoderm
c. ectoderm
d. mesoderm
