Download The Female Reproductive Cycle

CHAPTER 26
Reproduction and
Development
Figures 26.1 – 26.2
PowerPoint® Lecture Slides for
Essential Biology, Second Edition & Essential Biology with Physiology
Neil Campbell, Jane Reece, and Eric Simon
Presentation prepared by Chris C. Romero
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• During ejaculation, a man
releases up to 500 million
sperm, only one of which
may fertilize an egg
• You have trillions of cells
in your body, and they all
arose from one original
cell
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• An American woman is
4 times more likely to
deliver triplets today
than 25 years ago
• Even though a woman is
born with up to half a
million developing
gametes, she will only use
about 500 during her
lifetime
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BIOLOGY AND SOCIETY:
RISE OF THE SUPERTWINS
• On November 19, 1997, news reports heralded the
arrival of the Iowa septuplets
Figure 26.1
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• Other sets of multiple births soon followed
• What accounted for the sudden rash of multiple
births?
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• All of these multiple births were by women who had
taken fertility drugs because they couldn’t become
pregnant naturally
• Couples turn to fertility drugs to overcome their
natural reproductive limitations
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UNIFYING CONCEPTS OF ANIMAL
REPRODUCTION
• Reproduction is the creation of new individuals from
existing ones
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Asexual Reproduction
• In asexual reproduction
– One parent produces genetically identical offspring
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• Binary fission
– Is the simplest type of asexual reproduction
– Involves a single parent cell splitting through mitosis
into two genetically identical offspring cells
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• Some multicellular organisms reproduce by a
similar means called fission, in which one organism
splits into two or more individuals
Figure 26.2a
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• Fragmentation is the breaking of a parent body into
several pieces
• Regeneration, which follows fragmentation, is the
regrowth of a whole animal from the pieces
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• Budding
– Is the splitting off of
new individuals from
existing ones
Figure 26.2b
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• Asexual reproduction has a number of advantages
– It allows a species to perpetuate itself if its individual
members are sessile or isolated from one another
– It allows organisms to multiply quickly
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• One potential disadvantage of asexual reproduction
is that it produces genetically uniform populations
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Sexual Reproduction
• Sexual reproduction
– Involves the fusion of gametes (sperm and egg) from
two parents
– Increases the genetic variability among offspring
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• Some animals can
reproduce both
sexually and
asexually
Figure 26.3a
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• Some species are hermaphrodites with both male
and female reproductive systems
Figure 26.3b
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• The mechanics of fertilization play an important
part in sexual reproduction
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• Many organisms use external fertilization, in which
parents discharge their gametes into the water,
where fertilization occurs
Figure 26.3c
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• Other organisms use internal fertilization, which
occurs within the female’s body
• Internal fertilization requires copulation, or sexual
intercourse
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HUMAN REPRODUCTION
• Both sexes of humans have
– A pair of gonads, the organs that produce gametes
– Ducts to store and deliver the gametes
– Structures to facilitate copulation
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Female Reproductive Anatomy
• The ovaries
– Are the site of gamete production in human females
Ovaries
Oviduct
Follicles
Corpus luteum
Uterus
Wall of uterus
Cervix
(“neck” of
uterus)
Endometrium
(lining of uterus)
Vagina
Figure 26.4
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• The ovaries contain follicles
– Each follicle consists of a single developing egg
cell surrounded by layers of cells that nourish and
protect it
– The follicles also produce estrogen, the female sex
hormone
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• Ovulation
– Is the process by which an egg cell is ejected from
the follicle
Figure 26.5
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• The egg enters the oviduct, which is a tube in which
cilia sweep the egg toward the uterus
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• The uterus is the actual site of pregnancy
• The cervix, the narrow neck at the bottom of the
uterus, opens into the vagina, or birth canal
• During copulation, the vagina serves as a repository
for sperm
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• Female reproductive anatomy
Oviduct
Ovary
Rectum
(digestive
system)
Uterus
Bladder
(excretory
system)
Pubic bone
Urethra
(excretory
system)
Cervix
Vagina
Shaft
Glans
Prepuce
Clitoris
Labia minora
Labia majora
Vaginal opening
Figure 26.6
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Male Reproductive Anatomy
• The penis
– Contains erectile tissue
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• The testes
– Are the male gonads, enclosed in a sac called the
scrotum
– Produce sperm
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• Several glands
– Contribute to the formation of the fluid that carries,
nourishes, and protects sperm
• Semen
– Consists of this fluid and sperm
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• Male reproductive anatomy, side view
Bladder
(excretory
system)
Seminal
vesicle
Pubic bone
Rectum
(digestive
system
Erectile
tissue of
penis
Vas deferens
Urethra
Prostate gland
Vas
deferens Epididymis
Testis
Glans of
penis
Prepuce
Scrotum
Figure 26.7a
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• Male reproductive anatomy, front view
Bladder
(excretory
system)
Seminal vesicle
(behind bladder)
Prostate gland
Erectile tissue
of penis
Vas deferens
Urethra
Scrotum
Epididymis
Testis
Glans of penis
Figure 26.7b
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Gametogenesis
• Gametogenesis
– Is the production of gametes
• Human gametes
– Are haploid cells that develop by meiosis
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Oogenesis
• Oogenesis is the development of eggs within the
ovaries
Diploid cell
in embryo
Differentiation
and onset of
meiosis I
Ovary
Primary oocyte,
Completion of
meiosis I and
onset of
meiosis II
arrested in prophase
of meiosis I; present
at birth
Corpus
luteum
First polar body
Secondary oocyte,
Entry of sperm
triggers
completion of
meiosis II
Growing
follicle
arrested at
metaphase of meiosis
II; released from
ovary
Mature
follicle
Second polar body
Ovulation
Ruptured follicle
Ovum
(haploid)
Sperm
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Figure 26.8
Spermatogenesis
• Spermatogenesis
– Is the formation of sperm cells
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Epididymis
Penis
Testis
Scrotum
Diploid cell
Testis
Differentiation and
onset of meiosis I
Seminiferous
tubule
Primary spermatocyte
Cross section of
seminiferous
tubule
Meiosis I completed
Secondary spermatocyte
Meiosis II
Developing spermatids
Differentiation
Sperm cells
(haploid)
Center of seminiferous tubule
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Figure 26.9
The Female Reproductive Cycle
• Human females have a reproductive cycle, a
recurring series of events that produces gametes,
makes them available for fertilization, and prepares
the body for pregnancy
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• The female reproductive cycle involves two sets of
changes
– The ovarian cycle controls the growth and release of
an ovum
– The menstrual cycle prepares the uterus for possible
implantation of an embryo
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• Hormones
– Synchronize cyclical changes in the ovaries and
uterus
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• The female
reproductive
cycle
Control by hypothalamus
Hypothalamus
Releasing hormone
Inhibited by combination of
estrogen and progesterone
Stimulated by high levels
of estrogen
Anterior pituitary
(a)
1
Pituitary
hormones
in blood
4
(b)
2
FSH stimulates
follicle to grow
Ovarian cycle
Growing
follicle
LH peak triggers ovulation
5
Mature
follicle
Ovulation
Corpus
luteum
Degenerating
corpus luteum
(c)
Estrogen secreted by
growing follicle
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Progesterone and
estrogen secreted
by remnant of
follicle
Figure 26.10a–c
Ovarian
hormones
in blood
3
Peak causes
LH surge
7
Estrogen
Progesterone
(d)
Low levels trigger
menstruation
6
Progesterone
and estrogen
promote
thickening of
endometrium
Menstrual cycle
Endometrium
(e)
Menstruation
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Figure 26.10d, e
REPRODUCTIVE HEALTH
• Two issues of human reproductive health
– Contraception
– Transmission of disease
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Contraception
• Contraception
– Is the deliberate prevention of pregnancy
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• There are many
forms of
contraception, each
with varying degrees
of reliability
Figure 26.11
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• Contraceptive methods and their effectiveness
Table 26.1
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Sexually Transmitted Diseases
• Sexually transmitted diseases (STDs)
– Are contagious diseases spread by sexual contact
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• Viral STDs, such as AIDS, genital herpes, and
genital warts, cannot be cured but can be controlled
by medications
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• STDs caused by bacteria, protozoans, and fungi are
generally curable with drugs
Table 26.2
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REPRODUCTIVE TECHNOLOGIES
• Reproductive technologies
– Can help solve problems related to the inability to
conceive a child
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Infertility
• Infertility
– Is the inability to have children after one year of
trying
– Is most often due to problems in the man, such as
underproduction of sperm or impotence
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• Female infertility can result from a lack of eggs or a
failure to ovulate
• There are technologies available to help treat the
many forms of infertility
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In Vitro Fertilization
• In vitro fertilization (IVF)
– Happens under artificial, laboratory conditions
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• IVF
– Begins with the surgical removal of eggs and the
collection of sperm
– Involves fertilization of eggs in a petri dish
Figure 26.12
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• IVF
– Offers choices that nature does not
– Raises many moral and legal issues
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HUMAN DEVELOPMENT
• Embryonic development
– Begins with fertilization, the union of sperm and egg
to form a zygote
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Fertilization
• Copulation releases hundreds of millions of sperm
into the vagina, but only a few hundred survive the
trip to the egg, and only one will fertilize it
Figure 26.13
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• A mature human sperm
– Has a streamlined shape that suits its need to swim
through fluids in the vagina, uterus, and oviduct
Head
Plasma membrane
Mitochondria
Nucleus
Acrosome
Figure 26.14
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• The events of fertilization
2
1
The sperm
squeezes
through cells left
over from the
follicle.
The sperm’s
acrosomal
enzymes digest
the zona
pellucida.
3
The plasma
membranes of
the sperm and
egg fuse.
4
Acrosomal
enzymes
The sperm
enters the
egg
cytoplasm.
Sperm
Nucleus
Acrosome
Sperm
nucleus
Follicle
cell
Cytoplasm
5
The nuclei of
sperm and
egg join.
Plasma
membrane
Zona
pellucida
Egg cell
Figure 26.15
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Egg
nucleus
Zygote
nucleus
Basic Concepts of Embryonic Development
• The key to development in all organisms is that each
stage of development takes place in a highly
organized fashion
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Zygote
2 cells
Cleavage
4 cells
8 cells
Inner cell
mass
Many cells
(solid ball)
Blastocyst
(hollow ball)
Cross section
of blastocyst
Ectoderm
Mesoderm
Endoderm
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Gastrula
(cross section)
Gastrulation
Figure 26.16
• Development begins with cleavage, a series of rapid
cell divisions that results in a multicellular ball
• Cleavage continues as the embryo moves down the
oviduct toward the uterus
• About 6–7 days after fertilization, the embryo has
reached the uterus as a fluid-filled hollow ball of
about 100 cells called a blastocyst
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• The next stage of development is gastrulation, a
process that produces the three embryonic tissue
layers
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• Tissues and organs take shape in a developing
embryo as a result of many different changes in the
cells
Outer layer of ectoderm
Neural tube
Figure 26.17
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• In the process called induction, one group of cells
influences the development of an adjacent group of
cells
Lens
ectoderm
Optic cup
Cornea
Future
brain
Lens
Optic
vesicle
1
Optic
stalk
Future
retina
2
3
4
Figure 26.18
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Pregnancy and Early Development
• Pregnancy, or gestation
– Is the carrying of developing young within the
female reproductive tract
– Is measured as 40 weeks from the start of the last
menstrual cycle in humans
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• The early stages of human development begin with
fertilization and cleavage in the oviduct
Cleavage starts
Fertilization of ovum
Ovary
Oviduct
Secondary oocyte
Ovulation
Blastocyst (implanted)
Endometrium
Uterus
Figure 26.19
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• About one week after conception
– The embryo, which has become a blastocyst,
implants itself in the uterine wall
– The outer cell layer, the trophoblast, becomes part of
the placenta
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Endometrium
Inner cell mass
Endometrium
Blood vessel
(maternal)
Future embryo
Multiplying cells
of trophoblast
(future placenta)
Cavity
Future
yolk sac
Trophoblast
Trophoblast
Uterine cavity
(a) Blastocyst (6 days
after conception)
(b) Implantation underway (about 7 days)
Figure 26.20
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• The embryo after about a month after conception
Allantois
(forms part
of the
umbilical
cord)
Placenta
Mother’s
blood vessels
Amnion
Yolk
sac
Embryo
Chorion
Chorionic
villi
Figure 26.21
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• Four structures develop that assist the developing
embryo
– The amnion, a fluid filled sac that encloses and
protects the embryo
– The yolk sac, which produces the embryo’s first
blood and germ cells
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– The allantois, which forms part of the umbilical cord
– The chorion, which becomes part of the placenta
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The Stages of Pregnancy
• Pregnancy is divided into three trimesters
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The First Trimester
• A human embryo about 5 weeks after fertilization
Figure 26.22
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• A human embryo, now called a fetus, about 9 weeks
after fertilization
Figure 26.23
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• By the end of the first trimester
– The fetus looks like a miniature human being
– The sex of the fetus can be determined by ultrasound
Figure 26.24
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The Second Trimester
• The main developmental changes during the second
and third trimesters involve an increase in size and
general refinement of the human features
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• A fetus at 14 weeks, 2 weeks into the second
trimester
Figure 26.25
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• At 20 weeks, the fetus
– Is about 19 cm
(7.6 in.) long
and weighs
about half a
kilogram (1 lb)
– Has the face of
an infant
Figure 26.26
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The Third Trimester
• The third trimester
– Is a time of rapid growth
– Includes many important physical changes
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• At birth
– A typical baby is
about 50 cm (20 in.)
long and weighs
2.7–4.5 kg (6–10 lb)
Figure 26.27
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Childbirth
• The birth of a child is brought about by a series of
strong, rhythmic contractions of the uterus called
labor
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• Hormones play a key role in inducing labor
– Estrogen, oxytocin, and prostaglandins are all
involved
from
ovaries
Induces oxytocin
receptors on
uterus
Oxytocin
from fetus
and
pituitary
Stimulates uterus
to contract
Stimulates
placenta to make
Positive feedback
Estrogen
Prostaglandins
Simulate more
contractions of
uterus
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Figure 26.28
• The three stages
of labor
Figure 26.29
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EVOLUTION CONNECTION:
MENOPAUSE AND THE GRANDMOTHER
HYPOTHESIS
• Typically between the ages of 46 and 54, human
females undergo menopause, the cessation of
ovulation and menstruation
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• Why does the reproductive system shut down?
– One group of researchers proposed that menopause
actually increases a woman’s evolutionary fitness in
the long run
– Postreproductive women contribute to raising
grandchildren
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SUMMARY OF KEY CONCEPTS
• Gametogenesis
Oogenesis
Spermatogenesis
Primary
oocyte
Primary
spermatocyte
Once per month
Polar body
Secondary
oocyte
Secondary
spermatocyte
Spermatid
Fertilization
Sperm
Polar body
Ovum
Zygote
Visual Summary 26.1
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• In Vitro Fertilization
Collected egg
Implantation
Zygote
8-cell
embryo
In vitro fertilization
Collected sperm
Visual Summary 26.2
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• Basic Concepts of Embryonic Development
Gastrulation
Cleavage
Ectoderm
Mesoderm
Endoderm
Zygote
2-cell
embryo
Many-celled
solid ball
Blastocyst
(cross
section)
Gastrula
(cross
section)
Visual Summary 26.3
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