Chapter 42

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Transcript Chapter 42

BIOLOGY
Chapter 42: pp. 777 - 797
10th Edition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
two days
six weeks
three weeks
Sylvia S. Mader
Animal Development
five months
(2 days): Courtesy of the film Building Babies © ICAM/Mona Lisa; (3 weeks): © Lennart Nilsson, A Child is Born, 1990 Delacorte Press, pg. 81; (6 weeks): © Claude
Edelmann/Photo Researchers, Inc.; (5 months): © Derek Bromhall/OSF/Animals Animals/Earth Scenes
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
1
Outline

Early Developmental Stages





Developmental Process



Fertilization
Embryonic Development
Effect of Yolk
Neurulation and the Nervous System
Cellular Differentiation
Homeotic Genes
Human Embryonic and Fetal Development


Embryonic Development
Fetal Development
2
Early Developmental Stages

Fertilization requires that sperm and egg
interact to form a zygote

A human sperm cell has three parts:

The head


A middle piece


Contains a haploid nucleus covered by acrosome
containing enzymes, allowing the sperm to penetrate the
egg.
Contains ATP - producing mitochondria
The tail

A flagellum that allows the sperm to swim
3
Early Developmental Stages

An egg

Surrounded by the zona pellucida.
A few layers of adhering follicular cells, collectively
called the corona radiata.
 These cells nourished the egg when it was in a
follicle of the ovary.

4
Early Developmental Stages

Fertilization involves the following steps:
Several sperm penetrate the corona radiata
 Several sperm attempt to penetrate zona
pellucida
 One sperm enters the egg and their nuclei fuse

5
Fertilization
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
microvilli of oocyte plasma membrane
2. Acrosomal enzymes
digest a portion of
zona pellucida.
tail
1. Sperm makes its
way through the
corona radiata.
3. Sperm binds to and
fuses with oocyte
plasma membrane.
sperm
4. Sperm nucleus enters
cytoplasm of oocyte.
corona radiata
plasma
membrane
nucleus
5. Cortical granules
release enzymes;
zona pellucida
becomes fertilization
membrane.
middle
piece
head
acrosome
fertilization membrane
cortical granule
sperm pronucleus
6. Sperm and egg
pronuclei are enclosed
in a nuclear envelope.
oocyte plasma membrane
zona pellucida
egg pronucleus
© David M. Phillips/Visuals Unlimited; (Chick, p. 779): © Photodisc/Getty Images
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Embryonic Development

During first stages of development, an
organism is called an embryo

Following fertilization, zygote undergoes
cleavage

Morula forms blastula with a hollow blastocoel

Germ layers differentiate

Ectoderm

Mesoderm

Endoderm
7
Lancelet Early Development
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
Zygote
Cleavage is occurring.
blastocoel
Blastula
blastocoel
Gastrulation is occurring.
archenteron
mesoderm
ectoderm
endoderm
blastopore
Early gastrula
ectoderm
endoderm
b.
Late gastrula
a: © William Jorgensen/Visuals Unlimited; (Frog, p. 781): © Photodisc/Getty Images;
8
Comparative Development of Mesoderm
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
archenteron
ectoderm
mesoderm
endoderm
cross section
a. Lancelet late gastrula
archenteron
mesoderm
ectoderm yolk plug endoderm
longitudinal section
b. Frog late gastrula
archenteron primitive streak mesoderm
ectoderm
yolk
endoderm
cross section
c. Chick late gastrula
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Neurulation and the Nervous System

Nervous system
Develops from midline ectoderm located just
above the notochord
 Thickening of neural plate is seen along dorsal
surface of the embryo
 Neural folds develop on either side of neural
groove
 Neural grove becomes the neural tube

10
Development of Neural Tube and Coelom
in a Frog Embryo
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
presumptive
notochord
neural plate
neural groove
ectoderm
coelom
mesoderm
gut
gut
endoderm
notochord
archenteron
a.
neural tube
notochord0 coelom
b.
yolk
c.
d.
b: Courtesy Kathryn Tosney
11
Vertebrate Embryo, Cross Section
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
neural tube
somite
notochord
gut
coelom
ectoderm
mesoderm
endoderm
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Developmental Processes

Development requires:
Growth
 Cellular Differentiation
 Morphogenesis


Adult body cells are totipotent

Each contains all the instructions needed by
any other specialized cell in the body
13
Cytoplasmic Influence on Development
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
animal pole
Dorsal
plane of
first division
gray
crescent
Anterior
site of
sperm
fusion
Posterior
Ventral
vegetal pole
Dorsal
Anterior
Ventral
a. Zygote of a frog is polar and has axes.
Posterior
b. Each cell receives a part
of the gray crescent
c. Only the cell on the left
receives the gray crescent
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Induction
The ability of one embryonic tissue to
influence the development of another tissue
 Developmental path of cells is influenced
by neighboring cells

15
Control of Nervous System Development
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Host embryo has undergone gastrulation.
presumptive
ectoderm
ectoderm
presumptive
mesoderm
presumptive
endoderm
Presumptive nervous tissue is
removed from a donor embryo.
Host embryo undergoes
neurulation.
normal host
neural plate
tissue
transplant
After removal of host tissue, donor
presumptive nervous tissue is transplanted
to belly region of host embryo.
Due to normal induction process, a host
neural plate develops. But donated tissue
is not induced to develop into a neural
a.
Host embryo has undergone gastrulation.
Host embryo undergoes neurulation
normal host
neural plate
induced
neural plate
Presumptive notochord tissue is
removed from a donor embryo.
Donor presumptive notochord tissue is
transplanted to a host embryo. Host belly tissue
(which was removed) is returned to the host.
Host develops two neural plates—one induced
by host notochord tissue, the second induced
by transplanted notochord tissue.
b.
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Model Organisms
Roundworm, Caenorhabditis elegans
 Fruit Fly, Drosophila melanogaster
 Mouse, Mus musculus
 Fate Maps


Show the destiny of each cell as it arises
17
Development of C. elegans, a Nematode
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
egg
gonad
(8–16
divisions)
cuticle
(8–11
divisions)
gonad
vulva
(10–13
divisions)
cuticle
egg
intestine
(3–6
divisions)
nervous
system
(6–8
divisions)
vulva
sperm
intestine
nervous system
pharynx
(9–11
divisions)
pharynx
18
Development in Drosophila, a Fruit Fly
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Protein products of gap genes
b. Protein products of pair-rule genes
c. Protein products of segment-polarity genes
(All): Courtesy Steve Paddock, Howard Hughes Medical Research Institute
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Homeotic Genes

Homeotic Genes control pattern formation
Organization of differentiated cells into specific
three-dimensional structures
 Certain genes control whether a particular
segment will bear antennae, legs, or wings


Homeotic genes all contain the same
particular sequence of nucleotides, the
homeobox
Mice and humans have the same four clusters
of homeotic genes
 They are located on four different
chromosomes

20
Pattern Formation in Drosophila
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a.
Hox-2
Hox-1
mouse
chromosomes
Hox-3
Hox-4
fly chromosome
mouse
embryo
b.
fruit fly embryo
mouse
fruit fly
Courtesy E.B. Lewis
21
Extraembryonic Membranes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
embryo
allantois
amnion
yolk sac
chorion
Chick
embryo
chorion
amnion
allantois
umbilical
cord
yolk sac
fetal portion
of placenta
Human
maternal portion
of placenta
22
Human Development Before Implantation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2. Fertilization
egg nucleus
sperm nucleus
secondary oocyte
secondary oocyte
zona pellucida
corona radiata
5. Early blastocyst
single cell =
zygote
1. Ovulation
fimbriae
inner cell
mass
ovary
oviduct
2-cell
stage
6. Implantation
4-cell
stage
3. Cleavage
8-cell
stage
early chorion
4. Morula
(Fertilization): © Don W. Fawcett/Photo Researchers, Inc.; (2-cell): © Rawlins-CMSP/Getty Images; (Morula): © RBM Online/epa/Corbis; (Implantation): © Bettmann/Corbis
23
Human Embryonic and Fetal Development

Human gestation time - time from conception
to birth - approximately nine months

Embryonic Development - Months 1-2

Fetal Development - Months 3-9

Extra-embryonic Membranes

Chorion

Amnion

Allantois

Yolk Sac
24
Human Embryonic Development
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amniotic cavity
embryonic disk
yolk sac
blastocyst cavity
trophoblast
a. 14 days
amniotic cavity
embryo
yolk sac
chorionic villi
chorion
b. 18 days
body stalk
amniotic cavity
embryo
allantois
yolk sac
chorionic villi
c. 21 days
chorion
amniotic cavity
allantois
yolk sac
amnion
chorionic villi
d. 25 days
amniotic cavity
chorion
digestive tract
chorionic villi
amnion
umbilical cord
e. 35+ days
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Embryonic Development


First Week

Morula transformed into blastocyst

Gives rise to chorion
Second Week

Implanting begins

Gastrulation occurs

Inner cell mass flattened into embryonic disk

Ectoderm and Endoderm differentiate
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Embryonic Development

Third Week


Nervous system and circulatory system appear
Fourth and Fifth Weeks
Umbilical cord is fully formed
 Limb buds appear
 Head enlarges
 Sense organs more apparent

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Human Embryo at Beginning of Fifth Week
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
tail
brain
brain
optic
vesicle
optic
vesicle
tail
pharyngeal
pouch
pharyngeal
pouch
heart
region of
heart, liver
liver
limb bud
limb bud
umbilical
vessel
umbilical
vessel
a.
somite
b.
gastrointestinal tract
limb bud
a: © Lennart Nilsson, A Child is Born, Dell Publishing
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Embryonic Development

Sixth Through Eighth Weeks
Head achieves normal relationship with the
body
 Nervous system is developed enough to permit
reflex actions

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Structure and Function of the Placenta

The placenta
Begins formation once the embryo is fully
implanted
 Provides exchange between maternal and
embryonic circulations

Gases
 Nutrients
 Wastes

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Structure and Function of the Placenta

Chorionic villi

Project into the maternal tissues

Surrounded by maternal blood sinuses; the maternal
and fetal blood do not mix
Exchange between the fetal and maternal blood takes
place across the walls of the chorionic villi




CO2 and wastes move across from the fetus
O2 and nutrients flow from the maternal side
By the tenth week, the placenta is fully
formed
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Anatomy of the Placenta in a Fetus at Six
to Seven Months
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amniotic fluid
placenta
umbilical cord
endometrium
vagina
umbilical cord
umbilical blood vessel
chorionic villi
maternal
blood
vessels
Placenta
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Fetal Development and Birth

Fetal development (months 3–9) involves:




Extreme increase in size
The genitalia appear in the third month
A fetus soon acquires hair, eyebrows, eyelashes,
and nails
A fetus at first only flexes its limbs and nods its
head


Later it moves its limbs vigorously
A mother feels movements from the fourth month

After 16 weeks, a fetal heartbeat is heard through a
stethoscope.
 A fetus born at 24 weeks may survive
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Preventing and Testing for Birth Defects
It is believed that at least 1 in 16 newborns
has a birth defect
 Hereditary defects can sometimes be
detected before birth

Amniocentesis allows the fetus to be tested for
abnormalities of development;
 Chorionic villi sampling allows the embryo to
be tested;
 During preimplantation genetic diagnosis, eggs
are screened prior to in vitro fertilization

35
Three Methods for Genetic Defect Testing
Before Birth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
amniotic cavity
amniotic fluid
and fetal cells
biochemical studies
and chromosome analysis
fetal
cells
centrifuge
amniotic
fluid
cell culture
culture
medium
fetal cells
a. Amniocentesis
ultrasound scanner
suction tube
biochemical
studies and
chromosome
analysis
Cells from
chorionic villi
b. Chorionic villi sampling
laparoscope
ovary
uterus
aspirator
bladder
large
intestine
c. Preimplantation genetic diagnosis
chromosome
and genetic
analysis
oocytes from
ovaries
36
Preventing and Testing for Birth Defects

Have Good Health Habits


Avoid Alcohol, Smoking, and Drugs of Abuse



Alcohol consumption during pregnancy is a leading cause of
birth defects
Many preventable birth defects are caused by cigarette
smoking
Avoid Certain Medications and Supplements


Nutritious diet and avoid potentially harmful substances,
radiation, and pathogens
Even prescription drugs may cause birth defects
Avoid Having X-rays


Penetrating forms of radiation such as X-rays can hinder
cell division and damage DNA,
A particular concern for the rapidly dividing and
differentiating cells of a fetus.
37
Stages of Birth

When the fetal brain matures, the hypothalamus
causes the pituitary to stimulate the adrenal cortex
so that androgens are released.
 The placenta uses androgens as precursors for
estrogens that stimulate the production of
prostaglandin and oxytocin.
 The hormones estrogen, prostaglandin, and
oxytocin all cause the uterus to contract and expel
the fetus.
 The process of birth (parturition) has three stages:
dilation of the cervix, birth of the baby, and
expulsion of the placenta.
38
Three Stages of Parturition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
placenta
ruptured
amniotic
sac
a. First stage of birth: cervix dilates
b. Second stage of birth: baby emerges
placenta
uterus
umbilical
cord
c. Baby has arrived
d. Third stage of birth: expelling afterbirth
© Karen Kasmauski/Corbis.
39
Review

Early Developmental Stages





Developmental Process



Fertilization
Embryonic Development
Effect of Yolk
Neurulation and the Nervous System
Cellular Differentiation
Homeotic Genes
Human Embryonic and Fetal Development


Embryonic Development
Fetal Development
40
BIOLOGY
Chapter 42: pp. 777 - 797
10th Edition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
two days
six weeks
three weeks
Sylvia S. Mader
Animal Development
five months
(2 days): Courtesy of the film Building Babies © ICAM/Mona Lisa; (3 weeks): © Lennart Nilsson, A Child is Born, 1990 Delacorte Press, pg. 81; (6 weeks): © Claude
Edelmann/Photo Researchers, Inc.; (5 months): © Derek Bromhall/OSF/Animals Animals/Earth Scenes
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
41