Download First Trimester

An Introduction to Development and Inheritance
• Development
• Gradual modification of anatomical structures and
physiological characteristics from fertilization to
maturity
• Inheritance
• Transfer of genetic material from generation to
generation
© 2012 Pearson Education, Inc.
29-1 Development
• Differentiation
• Creation of different types of cells required in
development
• Occurs through selective changes in genetic activity
• As development proceeds, some genes are turned off,
others are turned on
• Fertilization
• Also called conception
• When development begins
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29-1 Development
• Embryological Development
• Occurs during first two months after fertilization
• Study of these events is called embryology
• Fetal Development
• Begins at start of ninth week
• Continues until birth
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29-1 Development
• Prenatal Development
• Embryological and fetal development stages
• Postnatal Development
• Commences at birth
• Continues to maturity, the state of full development
or completed growth
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29-1 Development
• Inheritance
• Transfer of genetically determined characteristics
from generation to generation
• Genetics
• Study of mechanisms responsible for inheritance
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29-2 Fertilization
• Fertilization
• Fusion of two haploid gametes, each containing
23 chromosomes
• Produces zygote containing 46 chromosomes
• Spermatozoon
• Delivers paternal chromosomes to fertilization site
• Travels relatively large distance
• Is small, efficient, and highly streamlined
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29-2 Fertilization
• Gamete
• Provides:
• Cellular organelles
• Inclusions
• Nourishment
• Genetic programming necessary to support
development of embryo for a week
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29-2 Fertilization
• Fertilization
• Occurs in uterine tube within a day after ovulation
• Secondary oocyte travels a few centimeters
• Spermatozoa must cover distance between vagina and
ampulla
• Capacitation
• Must occur before spermatozoa can fertilize secondary
oocyte
• Contact with secretions of seminal glands
• Exposure to conditions in female reproductive tract
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29-2 Fertilization
• Acrosomes
• Release hyaluronidase and acrosin, enzymes
• Penetrate corona radiata, zona pellucida, toward
oocyte surface
• Oocyte Activation
• Contact and fusion of cell membranes of sperm and
oocyte
• Follows fertilization
• Oocyte completes meiosis II, becomes mature ovum
© 2012 Pearson Education, Inc.
29-2 Fertilization
• Polyspermy
• Fertilization by more than one sperm
• Prevented by cortical reaction
• Cortical Reaction
• Releases enzymes that:
• Inactivate sperm receptors
• Harden zona pellucida
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29-2 Fertilization
• Female Pronucleus
• Nuclear material remaining in ovum after oocyte
activation
• Male Pronucleus
• Swollen nucleus of spermatozoon
• Migrates to center of cell
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29-2 Fertilization
• Amphimixis
• Fusion of female pronucleus and male pronucleus
• Moment of conception
• Cell becomes a zygote with 46 chromosomes
• Fertilization is complete
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29-2 Fertilization
• Cleavage
• Series of cell divisions
• Produces daughter cells
• Differentiation
• Involves changes in genetic activity of some cells but
not others
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Figure 29-1a Fertilization
A secondary oocyte and
numerous sperm at the time of
fertilization. Notice the
difference in size between the
gametes.
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Figure 29-1b Fertilization
Oocyte at Ovulation
Ovulation releases a secondary
oocyte and the first polar body;
both are surrounded by the corona
radiata. The oocyte is suspended in
metaphase of meiosis II.
Corona
radiata
Zona
pellucida
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First polar
body
Figure 29-1b Fertilization
Fertilization and Oocyte
Activation
Acrosomal enzymes from multiple
sperm create gaps in the corona
radiata. A single sperm then makes
contact with the oocyte membrane,
and membrane fusion occurs,
triggering oocyte activation and
completion of meiosis.
Fertilizing
spermatozoon
© 2012 Pearson Education, Inc.
Second polar
body
Figure 29-1b Fertilization
Pronucleus Formation
Begins
The sperm is absorbed into
the cytoplasm, and the female
pronucleus develops.
Nucleus of
fertilizing
spermatozoon
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Female
pronucleus
Figure 29-1b Fertilization
Spindle Formation and
Cleavage Preparation
The male pronucleus
develops, and spindle fibers
appear in preparation for the
first cleavage division.
Male
Female
pronucleus pronucleus
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Figure 29-1b Fertilization
Amphimixis Occurs and
Cleavage Begins
Metaphase of first
cleavage division
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Figure 29-1b Fertilization
Cleavage Begins
The first cleavage division
nears completion roughly
30 hours after fertilization.
Blastomeres
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29-3 Gestation
• Induction
• Cells release chemical substances that affect
differentiation of other embryonic cells
• Can control highly complex processes
• Gestation
• Time spent in prenatal development
• Consists of three integrated trimesters, each three
months long
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29-3 Gestation
1. First Trimester
• Period of embryological and early fetal development
• Rudiments of all major organ systems appear
2. Second Trimester
• Development of organs and organ systems
• Body shape and proportions change
3. Third Trimester
• Rapid fetal growth and deposition of adipose tissue
• Most major organ systems are fully functional
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29-4 The First Trimester
• First Trimester
• Includes four major stages
1. Cleavage
2. Implantation
3. Placentation
4. Embryogenesis
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29-4 The First Trimester
• Cleavage
• Sequence of cell divisions begins immediately after
fertilization
• Zygote becomes a pre-embryo, which develops into
multicellular blastocyst
• Ends when blastocyst contacts uterine wall
• Implantation
• Begins with attachment of blastocyst to endometrium
of uterus
• Sets stage for formation of vital embryonic structures
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29-4 The First Trimester
• Placentation
• Occurs as blood vessels form around periphery of
blastocyst and placenta develops
• Embryogenesis
• Formation of viable embryo
• Establishes foundations for all major organ systems
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29-4 The First Trimester
• The First Trimester
• Most dangerous period in prenatal life
• 40% of conceptions produce embryos that survive
past first trimester
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29-4 The First Trimester
• Cleavage and Blastocyst Formation
• Blastomeres
• Identical cells produced by cleavage divisions
• Morula
• Stage after three days of cleavage
• Pre-embryo is solid ball of cells resembling mulberry
• Reaches uterus on day 4
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29-4 The First Trimester
• Cleavage and Blastocyst Formation
• Blastocyst
• Formed by blastomeres
• Hollow ball with an inner cavity
• Known as blastocoele
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29-4 The First Trimester
• Cleavage and Blastocyst Formation
• Trophoblast
• Outer layer of cells separate outside world from
blastocoele
• Cells responsible for providing nutrients to
developing embryo
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29-4 The First Trimester
• Cleavage and Blastocyst Formation
• Inner cell mass
• Clustered at end of blastocyst
• Exposed to blastocoele
• Insulated from contact with outside environment by
trophoblast
• Will later form embryo
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Figure 29-2 Cleavage and Blastocyst Formation
Blastomeres
Polar bodies
4-cell stage
2-cell stage
DAY 1
First cleavage
division
DAY 0:
Fertilization
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DAY 2
Figure 29-2 Cleavage and Blastocyst Formation
Early morula
DAY 3
Advanced
morula
DAY 4
Hatching
Inner cell
mass
DAY 6
Blastocoele
Days 7–10:
Implantation in
uterine wall
(See Figure 29–3)
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Trophoblast
Blastocyst
29-4 The First Trimester
• Implantation
• Occurs (begins) seven days after fertilization
• Blastocyst adheres to uterine lining
• Trophoblast cells divide rapidly, creating several
layers
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29-4 The First Trimester
• Implantation
• Cellular trophoblast
• Cells closest to interior of blastocyst
• Syncytial trophoblast
• Outer layer
• Erodes path through uterine epithelium by secreting
hyaluronidase
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Figure 29-3 Stages in Implantation
DAY 6
FUNCTIONAL ZONE
OF ENDOMETRIUM
UTERINE
CAVITY
Uterine
glands
Blastocyst
DAY 7
Trophoblast
Blastocoele
Inner cell
mass
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Figure 29-3 Stages in Implantation
DAY 8
Syncytial
trophoblast
Cellular
trophoblast
DAY 9
Developing
villi
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Amniotic
cavity
Lacuna
29-4 The First Trimester
• Ectopic Pregnancy
• Implantation occurs outside uterus
• Does not produce viable embryo
• Can be life threatening
• Lacunae
• Trophoblastic channels carrying maternal blood
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29-4 The First Trimester
• Formation of the Amniotic Cavity
• Villi extend away from trophoblast into endometrium
• Increase in size and complexity until day 21
• Amniotic Cavity
• A fluid-filled chamber
• Inner cell mass is organized into an oval sheet two
layers thick
• Superficial layer faces amniotic cavity
• Deeper layer is exposed to fluid contents of
blastocoele
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29-4 The First Trimester
• Gastrulation and Germ Layer Formation
• Formation of third layer of cells
• Cells in specific areas of surface move toward central
line
• Known as primitive streak
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29-4 The First Trimester
• Primitive Streak
• Migrating cells leave surface and move between two
layers
• Creates three distinct embryonic layers, or germ layers
1. Ectoderm: consists of the superficial cells that did not
migrate into interior of inner cell mass
2. Endoderm: consists of cells that face blastocoele
3. Mesoderm: consists of poorly organized layer of
migrating cells between ectoderm and endoderm
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29-4 The First Trimester
• Ectodermal Contributions
• Integumentary system:
• Epidermis, hair follicles and hairs, nails, and glands
communicating with the skin (sweat glands, mammary
glands, and sebaceous glands)
• Skeletal system:
• Pharyngeal cartilages and their derivatives in adults
(portion of sphenoid, the auditory ossicles, the styloid
processes of the temporal bones, the cornu and superior
rim of the hyoid bone)*
• Nervous system:
• All neural tissue, including brain and spinal cord
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29-4 The First Trimester
• Ectodermal Contributions
• Endocrine system:
• Pituitary gland and adrenal medullae
• Respiratory system:
• Mucous epithelium of nasal passageways
• Digestive system:
• Mucous epithelium of mouth and anus, salivary glands
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29-4 The First Trimester
• Mesodermal Contributions
• Integumentary system:
• Dermis and hypodermis
• Skeletal system:
• All components except some pharyngeal derivatives
• Muscular system:
• All components
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29-4 The First Trimester
• Mesodermal Contributions
• Endocrine system:
• Adrenal cortex, endocrine tissues of heart, kidneys, and
gonads
• Cardiovascular system:
• All components
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29-4 The First Trimester
• Mesodermal Contributions
• Lymphatic system:
• All components
• Urinary system:
• The kidneys, including the nephrons and the initial portions
of the collecting system
• Reproductive system:
• The gonads and the adjacent portions of the duct systems
• Miscellaneous:
• The lining of the body cavities (pleural, pericardial, and
peritoneal) and the connective tissues that support all
organ systems
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29-4 The First Trimester
• Endodermal Contributions
• Endocrine system:
• Thymus, thyroid gland, and pancreas
• Respiratory system:
• Respiratory epithelium (except nasal passageways) and
associated mucous glands
• Digestive system:
• Mucous epithelium (except mouth and anus), exocrine
glands (except salivary glands), liver, and pancreas
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29-4 The First Trimester
• Endodermal Contributions
• Urinary system:
• Urinary bladder and distal portions of the duct system
• Reproductive system:
• Distal portions of the duct system, stem cells that
produce gametes
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29-4 The First Trimester
• Embryonic Disc
• Oval, three-layered sheet
• Produced by gastrulation
• Will form body of embryo
• Rest of blastocyst will be involved in forming
extraembryonic membranes
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Figure 29-4 The Inner Cell Mass and Gastrulation
Day 10: Yolk Sac Formation
Syncytial trophoblast
Cellular trophoblast
Amniotic cavity
Yolk sac
Blastocoele
Superficial layer
Deep layer
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Lacunae
Figure 29-4 The Inner Cell Mass and Gastrulation
Day 12: Gastrulation
Yolk sac
Amnion
Ectoderm
Mesoderm
Primitive
streak
Blastodisc
Endoderm
Embryonic disc
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29-4 The First Trimester
• Formation of the Extraembryonic Membranes
• Support embryological and fetal development
• Yolk sac
• Amnion
• Allantois
• Chorion
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29-4 The First Trimester
• The Yolk Sac
• Begins as layer of cells spread out around outer edges
of blastocoele to form complete pouch
• Important site of blood cell formation
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29-4 The First Trimester
• The Amnion
• Combination of mesoderm and ectoderm
• Ectodermal layer enlarges and cells spread over inner
surface of amniotic cavity
• Mesodermal cells create outer layer
• Continues to enlarge through development
• Amniotic fluid
• Surrounds and cushions developing embryo or fetus
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29-4 The First Trimester
• The Allantois
• Sac of endoderm and mesoderm
• Base later gives rise to urinary bladder
• The Chorion
• Combination of mesoderm and trophoblast
• Blood vessels develop within mesoderm
• Rapid-transit system for nutrients that links embryo with
trophoblast
• First step in creation of functional placenta
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29-4 The First Trimester
• Chorionic Villi
• In contact with maternal tissues
• Create intricate network within endometrium carrying
maternal blood
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Figure 29-5 Extraembryonic Membranes and Placenta Formation
Week 2
Migration of mesoderm around the inner surface of the
trophoblast creates the chorion. Mesodermal migration
around the outside of the amniotic cavity, between the
ectodermal cells and the trophoblast, forms the amnion.
Mesodermal migration around the endodermal pouch
creates the yolk sac.
Amnion
Syncytial
trophoblast
Cellular
trophoblast
Mesoderm
Yolk sac
Blastocoele
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Chorion
Figure 29-5 Extraembryonic Membranes and Placenta Formation
Week 3
The embryonic disc bulges into the amniotic cavity at the
head fold. The allantois, an endodermal extension
surrounded by mesoderm, extends toward the trophoblast.
Amniotic cavity
(containing
amniotic fluid)
Allantois
Yolk
sac
Head fold
of embryo
Chorion
Syncytial
trophoblast
Chorionic villi
of placenta
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Figure 29-5 Extraembryonic Membranes and Placenta Formation
Week 4
The embryo now has a head fold and a tail fold. Constriction
of the connections between the embryo and the surrounding
trophoblast narrows the yolk stalk and body stalk.
Tail fold
Body stalk
Yolk stalk
Yolk sac
Embryonic gut
Embryonic
head fold
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Figure 29-5 Extraembryonic Membranes and Placenta Formation
Week 5
The developing embryo and extraembryonic
membranes bulge into the uterine cavity. The
trophoblast pushing out into the uterine lumen remains
covered by endometrium but no longer participates in
nutrient absorption and embryo support. The embryo
moves away from the placenta, and the body stalk and
yolk stalk fuse to form an umbilical stalk.
Uterus
Myometrium
Decidua
basalis
Umbilical stalk
Placenta
Yolk sac
Chorionic villi
of placenta
Decidua
capsularis
Decidua
parietalis
Uterine lumen
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Figure 29-5 Extraembryonic Membranes and Placenta Formation
Decidua
parietalis
Decidua basalis
Umbilical cord
Placenta
Amniotic cavity
Week 10
The amnion has expanded
greatly, filling the uterine cavity.
The fetus is connected to the
placenta by an elongated umbilical
cord that contains a portion of the
allantois, blood vessels, and the
remnants of the yolk stalk.
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Amnion
Chorion
Decidua
capsularis
29-4 The First Trimester
• Placentation
• Body stalk
• Connection between embryo and chorion
• Contains distal portions of allantois and blood vessels
that carry blood to and from placenta
• Yolk stalk
• Narrow connection between endoderm of embryo and
yolk sac
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29-4 The First Trimester
• Decidua Capsularis
• Thin portion of endometrium
• No longer participates in nutrient exchange and
chorionic villi in region disappear
• Decidua Basalis
• Disc-shaped area in deepest portion of endometrium
• Where placental functions are concentrated
• Decidua Parietalis
• Rest of the uterine endometrium
• No contact with chorion
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29-4 The First Trimester
• Umbilical Cord
• Connects fetus and placenta
• Contains allantois, placental blood vessels, and yolk
stalk
• Placental Circulation
• Through paired umbilical arteries
• Returns in single umbilical vein
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Figure 29-6a A Three-Dimensional View of Placental Structure
Chorionic
villi
Umbilical
vein
Umbilical
arteries
Area filled with
maternal blood
Amnion Trophoblast (cellular
and syncytial layers)
Maternal
blood vessels
Arrows in the enlarged view indicate the direction
of blood flow.
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29-4 The First Trimester
• The Endocrine Placenta
• Synthesized by syncytial trophoblast, released into
maternal bloodstream
• Human chorionic gonadotropin (hCG)
• Human placental lactogen (hPL)
• Placental prolactin
• Relaxin
• Progesterone
• Estrogens
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29-4 The First Trimester
• Human Chorionic Gonadotropin (hCG)
• Appears in maternal bloodstream soon after
implantation
• Provides reliable indication of pregnancy
• Pregnancy ends if absent
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29-4 The First Trimester
• Human Placental Lactogen (hPL)
• Human chorionic somatomammotropin (hCS)
• Prepares mammary glands for milk production
• Synergistic with growth hormone at other tissues
• Ensures adequate glucose and protein is available
for the fetus
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29-4 The First Trimester
• Placental Prolactin
• Helps convert mammary glands to active status
• Relaxin
• A peptide hormone secreted by placenta and corpus
luteum during pregnancy
• Increases flexibility of pubic symphysis, permitting pelvis
to expand during delivery
• Causes dilation of cervix
• Suppresses release of oxytocin by hypothalamus and
delays labor contractions
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29-4 The First Trimester
• Embryogenesis
• Body of embryo begins to separate from embryonic
disc
• Body of embryo and internal organs start to form
• Folding, differential growth of embryonic disc produces
bulge that projects into amniotic cavity
• Projections are head fold and tail fold
• Organogenesis
• Process of organ formation
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Figure 29-7a The First 12 Weeks of Development
Future head
of embryo
Thickened
neural plate
(will form brain)
Axis of future
spinal cord
Somites
Neural folds
Cut wall of
amniotic cavity
Future tail
of embryo
Week 2. An SEM of the superior surface of a monkey
embryo at 2 weeks of development. A human embryo
at this stage would look essentially the same.
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Figure 29-7b The First 12 Weeks of Development
Medulla
oblongata
Ear
Pharyngeal
arches
Forebrain
Eye
Heart
Somites
Body
stalk
Arm bud
Tail
Leg bud
Week 4. Fiberoptic view of human
development at week 4.
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Figure 29-7c The First 12 Weeks of Development
Chorionic
villi
Amnion
Umbilical
cord
Placenta
Week 8. Fiberoptic view of human
development at week 8.
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Figure 29-7d The First 12 Weeks of Development
Amnion
Umbilical
cord
Week 12. Fiberoptic view of human
development at week 12.
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29-5 The Second and Third Trimesters
• Second Trimester
• Fetus grows faster than surrounding placenta
• Third Trimester
• Most of the organ systems become ready
• Growth rate starts to slow
• Largest weight gain
• Fetus and enlarged uterus displace many of mother’s
abdominal organs
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Figure 29-8a The Second and Third Trimesters
A four-month-old fetus, seen through a fiberoptic endoscope
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Figure 29-8b The Second and Third Trimesters
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Head of a six-month-old fetus, revealed
through ultrasound
Figure 29-9a Growth of the Uterus and Fetus
Placenta
Uterus
Umbilical
cord
Fetus at
16 weeks
Amniotic fluid
Cervix
Vagina
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Pregnancy at 16 weeks, showing the
positions of the uterus, fetus, and placenta.
Figure 29-9b Growth of the Uterus and Fetus
9 months
8 months
7 months
6 months
5 months
After dropping,
in preparation
to delivery
4 months
3 months
Pregnancy at three months to nine months
(full term), showing the superior-most
position of the uterus within the abdomen.
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Figure 29-9c Growth of the Uterus and Fetus
Stomach
Liver
Small intestine
Transverse
colon
Fundus
of uterus
Pancreas
Aorta
Common
iliac vein
Cervical (mucus)
plug in cervical canal
Placenta
Umbilical cord
Urinary bladder
Pubic symphysis
Vagina
Urethra
Pregnancy at full term. Note the positions of the
uterus and full-term fetus within the abdomen,
and the displacement of abdominal organs.
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External os
Rectum
Figure 29-9d Growth of the Uterus and Fetus
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A sectional view through the
abdominopelvic cavity of a woman
who is not pregnant.
29-5 The Second and Third Trimesters
• Pregnancy and Maternal Systems
• Developing fetus is totally dependent on maternal organ
systems for nourishment, respiration, and waste
removal
• Maternal adaptations include increases in:
• Respiratory rate and tidal volume
• Blood volume
• Nutrient and vitamin intake
• Glomerular filtration rate
• Size of uterus and mammary glands
© 2012 Pearson Education, Inc.
29-5 The Second and Third Trimesters
•
•
Progesterone
•
Released by placenta
•
Has inhibitory effect on uterine smooth muscle
•
Prevents extensive, powerful contractions
Opposition to Progesterone
•
Three major factors
1. Rising estrogen levels
2. Rising oxytocin levels
3. Prostaglandin production
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29-5 The Second and Third Trimesters
• Structural and Functional Changes in the Uterus
• False labor
• Occasional spasms in uterine musculature
• Contractions not regular or persistent
• True labor
• Results from biochemical and mechanical factors
• Continues due to positive feedback
• Labor contractions
• Begin in myometrium
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29-6 Labor
• Parturition
• Is forcible expulsion of fetus
• Contractions
• Begin near top of uterus, sweep in wave toward
cervix
• Strong, occur at regular intervals, increase in force
and frequency
• Change position of fetus, move it toward cervical
canal
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29-6 Labor
• Stages of Labor
1. Dilation stage
2. Expulsion stage
3. Placental stage
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29-6 Labor
• Dilation Stage
• Begins with onset of true labor
• Cervix dilates
• Fetus begins to shift toward cervical canal
• Highly variable in length, but typically lasts over eight
hours
• Frequency of contractions steadily increases
• Amniochorionic membrane ruptures (water breaks)
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Figure 29-11 The Stages of Labor
Fully developed fetus before labor begins
Pubic
symphysis
Placenta Umbilical Sacral Cervical Cervix Vagina
cord promontory canal
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Figure 29-11 The Stages of Labor
The Dilation Stage
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29-6 Labor
• Expulsion Stage
• Begins as cervix completes dilation
• Contractions reach maximum intensity
• Continues until fetus has emerged from vagina
• Typically less than two hours
• Delivery
• Arrival of newborn infant into outside world
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29-6 Labor
• Episiotomy
• Incision through perineal musculature
• Needed if vaginal canal is too small to pass fetus
• Repaired with sutures after delivery
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29-6 Labor
• Cesarean Section (C-section)
• Removal of infant by incision made through
abdominal wall
• Opens uterus just enough to pass infant’s head
• Needed if complications arise during dilation or
expulsion stages
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Figure 29-11 The Stages of Labor
The Expulsion Stage
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29-6 Labor
• Placental Stage
• Muscle tension builds in walls of partially empty uterus
• Tears connections between endometrium and placenta
• Ends within an hour of delivery with ejection of
placenta, or afterbirth
• Accompanied by a loss of blood
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Figure 29-11 The Stages of Labor
The Placental Stage
Uterus
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Ejection of the
placenta
29-6 Labor
• Premature Labor
• Occurs when true labor begins before fetus has
completed normal development
• Newborn’s chances of surviving are directly
related to body weight at delivery
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29-6 Labor
• Immature Delivery
• Refers to fetuses born at 25–27 weeks of gestation
• Most die despite intensive neonatal care
• Survivors have high risk of developmental
abnormalities
• Premature Delivery
• Refers to birth at 28–36 weeks
• Newborns have a good chance of surviving and
developing normally
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29-6 Labor
• Difficult Deliveries
• Forceps delivery
• Needed when fetus faces mother’s pubis instead of
sacrum
• Risks to infant and mother are reduced if forceps are
used
• Forceps resemble large, curved salad tongs
• Used to grasp head of fetus
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29-6 Labor
• Difficult Deliveries
• Breech birth
• Legs or buttocks of fetus enter vaginal canal first instead
of head
• Umbilical cord can become constricted, cutting off
placental blood flow
• Cervix may not dilate enough to pass head
• Prolongs delivery
• Subjects fetus to severe distress and potential injury
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29-6 Labor
• Multiple Births
• Dizygotic twins
• Also called “fraternal” twins
• Develop when two separate oocytes were ovulated and
subsequently fertilized
• Genetic makeup not identical
• 70% of twins
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29-6 Labor
• Multiple Births
• Monozygotic twins
• Also called “identical” twins
• Result either from:
• Separation of blastomeres early in cleavage
• Splitting of inner cell mass before gastrulation
• Genetic makeup is identical because both formed from
same pair of gametes
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29-6 Labor
• Multiple Births
• Conjoined twins
• Siamese twins
• Genetically identical twins
• Occurs when splitting of blastomeres or of
embryonic disc is not completed
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29-6 Labor
• Rates of Multiple Births
• Twins in 1 of every 89 births
• Triplets in 1 of every 892 (7921) births
• Quadruplets in 1 of every 893 (704,969) births
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29-7 Postnatal Life
• Five Life Stages
1. Neonatal period
2. Infancy
3. Childhood
4. Adolescence
5. Maturity
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29-7 Postnatal Life
• Duration of Life Stages
• Neonatal Period: extends from birth to 1 month
• Infancy: 1 month to 2 years of age
• Childhood: 2 years until adolescence
• Adolescence: period of sexual and physical
maturation
• Senescence: process of aging that begins at end of
development (maturity)
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29-7 Postnatal Life
• The Neonatal Period, Infancy, and Childhood
• Two major events occur
1. Organ systems become fully operational
2. Individual grows rapidly and body proportions change
significantly
• Pediatrics
•
Medical specialty focusing on postnatal development
from infancy to adolescence
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29-7 Postnatal Life
• The Neonatal Period
• Transition from fetus to neonate
• Neonate
• Newborn
• Systems begin functioning independently
• Respiratory
• Circulatory
• Digestive
• Urinary
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29-7 Postnatal Life
• Lactation and the Mammary Glands
• Colostrum
• Secretion from mammary glands
• Ingested by infant during first two to three days
• Contains more proteins and less fat than breast milk
• Many proteins are antibodies that help ward off
infections until immune system is functional
• Mucins present inhibit replication of rotaviruses
• As production drops, mammary glands convert to milk
production
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29-7 Postnatal Life
• Breast Milk
• Consists of water, proteins, amino acids, lipids,
sugars, and salts
• Also contains large quantities of lysozymes—enzymes
with antibiotic properties
• Milk let-down reflex
• Mammary gland secretion triggered when infant sucks
on nipple
• Continues to function until weaning, typically one to two
years
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Figure 29-12 The Milk Let-Down Reflex
Stimulation of Hypothalamic
Nuclei
Posterior
lobe of the
pituitary
gland
Oxytocin Release
Milk Ejected
Start
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Stimulation of Tactile Receptors
Neural Impulse Transmission
29-7 Postnatal Life
• Infancy and Childhood
• Growth occurs under direction of circulating
hormones
• Growth hormone
• Adrenal steroids
• Thyroid hormones
• Growth does not occur uniformly
• Body proportions gradually change
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Figure 29-13 Growth and Changes in Body Form and Proportion
Prenatal Development
Embryological Development
Fetal Development
4 weeks
8 weeks
16 weeks
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Figure 29-13 Growth and Changes in Body Form and Proportion
Postnatal Development
Neonatal
Infancy
1 month
2 years
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Childhood
Adolescence
Puberty
(between 9–14 years)
Maturity
18 years
29-7 Postnatal Life
• Adolescence and Maturity
• Puberty is a period of sexual maturation and marks
the beginning of adolescence
•
Generally starts at age 12 in boys, age 11 in girls
• Three major hormonal events interact
1. Hypothalamus increases production of GnRH
2. Circulating levels of FSH and LH rise rapidly
3. Ovarian or testicular cells become more sensitive to
FSH and LH
• Hormonal changes produce sex-specific differences
in structure and function of many systems
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29-7 Postnatal Life
• Adolescence
• Begins at puberty
• Continues until growth is completed
• Maturity (Senescence)
• Aging
• Reduces functional capabilities of individual
• Affects homeostatic mechanisms
• Sex hormone levels decline at menopause or male
climacteric
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29-7 Postnatal Life
• Geriatrics
• Medical specialty dealing with problems
associated with aging
• Trained physicians, or geriatricians
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Figure 29-19 A Map of Human Chromosomes
Color Blindness (multiple forms) Chapter 17
Fragile-X Syndrome Chapter 29
Hemophilia
Chapter 19
Gaucher’s Disease
Neurofibromatosis, Type 2
Lysosomal storage disease caused
by excess glycolipids in plasma membranes
Tumors of the auditory nerves
and tissues surrounding the brain
Familial Colon Cancer*
Down’s Syndrome
Chapter 24
Chapter 29
Retinitis Pigmentosa*
Amyotrophic Lateral Sclerosis*
Chapter 17
Huntington’s Disease*
Chapter 15
ADA Deficiency
Chapter 17
Familial Polyposis of the Colon
An enzyme deficiency that
affects the immune system
Abnormal tissue growths that
commonly lead to colon cancer
Familial Hypercholesterolemia
Extremely high cholesterol
Myotonic Dystrophy
Form of muscular dystrophy in
which symptoms often
develop after puberty
Amyloidosis
Accumulation of an insoluble
fibrillar protein in the tissues
Breast Cancer*
Chapter 28
Y1 2
3
22 X
4
21
5
20
19
6
CHROMOSOME
18
7
PAIRS
17
8
16
9
10
15
11
14 13 12
Polycystic Kidney Disease
Cystic Fibrosis
Chapter 23
Burkitt’s Lymphoma
Cancer of lymphocytes; a
type of non-Hodgkin lymphoma
Retinitis Pigmentosa*
Chapter 14
Lysosomal storage disease
affecting neural tissue
Malignant Melanoma
Chapter 5
Marfan’s Syndrome
Ovarian Cancer
Chapter 6
Chapter 28
Alzheimer’s Disease*
Multiple Endocrine Neoplasia, Type 2
Chapter 16
Tumors in endocrine glands and
other tissues
SCID Chapter 22
1-Antitrypsin Deficiency
Causes a predisposition to
develop emphysema
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Destroys neurons in the brain
and spinal cord, resulting in
loss of muscle control
Epilepsy, progressive
Tay–Sachs Disease
A relatively common tumor of the eye,
accounting for 2% of childhood malignancies
Spinocerebellar Ataxia
Chapter 17
Chapter 26
Retinoblastoma
Muscular Dystrophy Chapter 10
Prostate Cancer Chapter 28
PKU
(phenylketonuria)
Chapter 25
Diabetes Mellitus, Type 1
Chapter 18
Sickle Cell Anemia Chapter 19
* One form of the disease