169 Ch 29_lecture_presentation

© 2012 Pearson Education, Inc.
PowerPoint®
Lecture Presentations prepared by
Jason LaPres
Lone Star College—North Harris
29
Development and
Inheritance

An Introduction to Development and Inheritance
• Learning Outcomes
• 29-1 Explain the relationship between
differentiation and development, and specify
the various stages of development.
• 29-2 Describe the process of fertilization, and
explain how developmental processes are
regulated.
• 29-3 List the three stages of prenatal
development, and describe the major events
of each.

• 29-4 Explain how the three germ layers
participate in the formation of
extraembryonic membranes, and discuss the
importance of the placenta as an endocrine
organ.
• 29-5 Describe the interplay between the maternal
organ systems and the developing fetus, and
discuss the structural and functional
changes in the uterus during gestation.

• 29-6 List and discuss the events that occur during
labor and delivery.
• 29-7 Identify the features and physiological
changes of the postnatal stages of life.
• 29-8 Relate basic principles of genetics to the
inheritance of human traits.

• Development
• Gradual modification of anatomical structures and
physiological characteristics from fertilization to
maturity
• Inheritance
• Transfer of genetic material from generation to
generation

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

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

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

29-1 Development
• Inheritance
• Transfer of genetically determined characteristics
from generation to generation
• Genetics
• Study of mechanisms responsible for inheritance

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

29-2 Fertilization
• Gamete
• Provides:
• Cellular organelles
• Inclusions
• Nourishment
• Genetic programming necessary to support
development of embryo for a week

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

29-2 Fertilization
• Hyaluronidase
• Enzyme breaks down bonds between adjacent follicle
cells
• Allows spermatozoon to reach oocyte
• Acrosin
• Is a proteolytic enzyme
• Is required to reach oocyte

29-2 Fertilization
• Acrosomes
• Release hyaluronidase and acrosin
• 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

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

29-2 Fertilization
• Female Pronucleus
• Nuclear material remaining in ovum after oocyte
activation
• Male Pronucleus
• Swollen nucleus of spermatozoon
• Migrates to center of cell

29-2 Fertilization
• Amphimixis
• Fusion of female pronucleus and male pronucleus
• Moment of conception
• Cell becomes a zygote with 46 chromosomes
• Fertilization is complete

29-2 Fertilization
• Cleavage
• Series of cell divisions
• Produces daughter cells
• Differentiation
• Involves changes in genetic activity of some cells but
not others

Figure 29-1a Fertilization
A secondary oocyte and
numerous sperm at the time of
fertilization. Notice the
difference in size between the
gametes.

Figure 29-1b Fertilization
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
First polar
body
Zona
pellucida
Oocyte at Ovulation

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
Second polar
body
Fertilization and Oocyte
Activation

Pronucleus Formation
Begins
The sperm is absorbed into
the cytoplasm, and the female
pronucleus develops.
Nucleus of
fertilizing
spermatozoon
Female
pronucleus

Spindle Formation and
Cleavage Preparation
The male pronucleus
develops, and spindle fibers
appear in preparation for the
first cleavage division.
Female
pronucleus
Male
pronucleus

Amphimixis Occurs and
Cleavage Begins
Metaphase of first
cleavage division

The first cleavage division
nears completion roughly
30 hours after fertilization.
Cleavage Begins
Blastomeres

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

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

29-4 The First Trimester
• First Trimester
• Includes four major stages
1. Cleavage
2. Implantation
3. Placentation
4. Embryogenesis

• 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

• 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

• The First Trimester
• Most dangerous period in prenatal life
• 40% of conceptions produce embryos that survive
past 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

• Blastocyst
• Formed by blastomeres
• Hollow ball with an inner cavity
• Known as blastocoele

• Trophoblast
• Outer layer of cells separate outside world from
blastocoele
• Cells responsible for providing nutrients to
developing embryo

• Inner cell mass
• Clustered at end of blastocyst
• Exposed to blastocoele
• Insulated from contact with outside environment by
trophoblast
• Will later form embryo

Figure 29-2 Cleavage and Blastocyst Formation
Polar bodies
2-cell stage
DAY 1 DAY 2
4-cell stage
Blastomeres
DAY 0:
First cleavage
division
Fertilization

Figure 29-2 Cleavage and Blastocyst Formation
Early morula
DAY 3
DAY 4
DAY 6
Advanced
morula
Hatching
Inner cell
mass
Blastocoele
Trophoblast
Blastocyst
Days 7–10:
Implantation in
uterine wall
(See Figure 29–3)

• Implantation
• Occurs seven days after fertilization
• Blastocyst adheres to uterine lining
• Trophoblast cells divide rapidly, creating several
layers

• Implantation
• Cellular trophoblast
• Cells closest to interior of blastocyst
• Syncytial trophoblast
• Outer layer
• Erodes path through uterine epithelium by secreting
hyaluronidase

Figure 29-3 Stages in Implantation
DAY 6 FUNCTIONAL ZONE
OF ENDOMETRIUM
DAY 7
UTERINE
CAVITY
Uterine
glands
Blastocyst
Trophoblast
Blastocoele
Inner cell
mass

Figure 29-3 Stages in Implantation
DAY 8
Syncytial
trophoblast
Cellular
trophoblast
Amniotic
cavity
Lacuna
Developing
villi
DAY 9

• Ectopic Pregnancy
• Implantation occurs outside uterus
• Does not produce viable embryo
• Can be life threatening
• Lacunae
• Trophoblastic channels carrying maternal blood

• 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

• 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

• 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

• 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

• 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

• Mesodermal Contributions
• Integumentary system:
• Dermis and hypodermis
• Skeletal system:
• All components except some pharyngeal derivatives
• Muscular system:
• All components

• Adrenal cortex, endocrine tissues of heart, kidneys, and
gonads
• Cardiovascular system:
• All components

• 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

• Endodermal Contributions
• 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

• 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

• Embryonic Disc
• Oval, three-layered sheet
• Produced by gastrulation
• Will form body of embryo
• Rest of blastocyst will be involved in forming
extraembryonic membranes

Figure 29-4 The Inner Cell Mass and Gastrulation
Superficial layer
Deep layer
Day 10: Yolk Sac Formation
Lacunae
Blastocoele
Yolk sac
Amniotic cavity
Cellular trophoblast
Syncytial trophoblast

Figure 29-4 The Inner Cell Mass and Gastrulation
Day 12: Gastrulation
Amnion
Ectoderm
Primitive
streak
Blastodisc
Yolk sac
Mesoderm
Endoderm
Embryonic disc

• Formation of the Extraembryonic Membranes
• Support embryological and fetal development
• Yolk sac
• Amnion
• Allantois
• Chorion

• 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

• 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

• 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

• Chorionic Villi
• In contact with maternal tissues
• Create intricate network within endometrium carrying
maternal blood

Figure 29-5 Extraembryonic Membranes and Placenta Formation
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.
Week 2
Amnion
Syncytial
trophoblast
Cellular
trophoblast
Mesoderm
Yolk sac
Blastocoele
Chorion

The embryonic disc bulges into the amniotic cavity at the
head fold. The allantois, an endodermal extension
surrounded by mesoderm, extends toward the trophoblast.
Week 3
Amniotic cavity
(containing
amniotic fluid)
Allantois
Head fold
of embryo
Syncytial
trophoblast
Chorion
Yolk
sac
Chorionic villi
of placenta

Embryonic
head fold
Embryonic gut
Yolk sac
Yolk stalk
Body stalk
Tail fold
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.
Week 4

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
Chorionic villi
of placenta
Umbilical stalk
Placenta
Yolk sac
Decidua
capsularis
Decidua
parietalis
Uterine lumen
Decidua
basalis

Decidua
capsularis
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.
Chorion
Amnion
Amniotic cavity
Placenta
Umbilical cord
Decidua
parietalis
Decidua basalis

• 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

• 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

• 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

Figure 29-6a A Three-Dimensional View of Placental Structure
Chorion
Amnion
Decidua
capsularis
Umbilical
cord (cut) Placenta
Yolk sac
Decidua basalis
A view of the uterus after the fetus has been removed and the
umbilical cord cut.

A view of the uterus after the fetus has
been removed and the umbilical cord cut.
Cervix
Vagina
External os
Cervical
(mucous)
plug in
cervical
canal
Uterine
cavity
Decidua
parietalis
Myometrium

Chorionic
villi
Umbilical
arteries
Umbilical
vein
Area filled with
maternal blood
Arrows in the enlarged view indicate the direction
of blood flow.
Maternal
blood vessels
Trophoblast (cellular
and syncytial layers)
Amnion

Figure 29-6b A Three-Dimensional View of Placental Structure
Fetal blood
vessels
Syncytial
trophoblast
Embryonic
connective tissue
Area filled with
maternal blood
A cross section through a chorionic villus,
showing the syncytial trophoblast exposed
to the maternal blood space.
LM × 280Chorionic villus

• The Endocrine Placenta
• Synthesized by syncytial trophoblast, released into
maternal bloodstream
• Human chorionic gonadotropin (hCG)
• Human placental lactogen (hPL)
• Placental prolactin
• Relaxin
• Progesterone
• Estrogens

• Human Chorionic Gonadotropin (hCG)
• Appears in maternal bloodstream soon after
implantation
• Provides reliable indication of pregnancy
• Pregnancy ends if absent

• 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

• 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

• 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

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.

Figure 29-7b The First 12 Weeks of Development
Tail
Body
stalk
Heart
Eye
Forebrain
Ear
Medulla
oblongata
Week 4. Fiberoptic view of human
development at week 4.
Leg bud
Arm bud
Somites
Pharyngeal
arches

Figure 29-7c The First 12 Weeks of Development
Umbilical
cord
Amnion
Placenta
Chorionic
villi

Figure 29-7d The First 12 Weeks of Development
Umbilical
cord
Amnion

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

Table 29-2 An Overview of Prenatal Development

Figure 29-8a The Second and Third Trimesters
A four-month-old fetus, seen through a fiberoptic endoscope

Figure 29-8b The Second and Third Trimesters
Head of a six-month-old fetus, revealed
through ultrasound

Figure 29-9a Growth of the Uterus and Fetus
Placenta
Umbilical
cord
Fetus at
16 weeks
Uterus
Amniotic fluid
Cervix
Vagina
Pregnancy at 16 weeks, showing the
positions of the uterus, fetus, and placenta.

Figure 29-9b Growth of the Uterus and Fetus
After dropping,
in preparation
to delivery
Pregnancy at three months to nine months
(full term), showing the superior-most
position of the uterus within the abdomen.
9 months
8 months
7 months
6 months
5 months
4 months
3 months

Figure 29-9c Growth of the Uterus and Fetus
Stomach
Transverse
colon
Liver
Fundus
of uterus
Small intestine
Pancreas
Aorta
Common
iliac vein
Cervical (mucus)
plug in cervical canal
External os
Rectum
Urethra
Vagina
Pubic symphysis
Urinary bladder
Placenta
Umbilical cord
Pregnancy at full term. Note the positions of the
uterus and full-term fetus within the abdomen,
and the displacement of abdominal organs.

Figure 29-9d Growth of the Uterus and Fetus
A sectional view through the
abdominopelvic cavity of a woman
who is not pregnant.

• 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

• 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

• 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

Figure 29-10 Factors Involved in the Initiation of Labor and Delivery
Placental estrogens increase the sensitivity of the
smooth muscle cells of the myometrium and make
contractions more likely. As delivery approaches, the
production of estrogens accelerates. Estrogens also
increase the sensitivity of smooth muscle fibers to
oxytocin.
Placental Factors Fetal Factors
Relaxin produced
by the placenta
relaxes the pelvic
articulations and
dilates the cervix.
Growth and the
increase in fetal
weight stretches
and distorts the
myometrium.
Fetal pituitary
releases
oxytocin in
response to
estrogens.
Distortion of the myometrium
increases the sensitivity of the
smooth muscle layers, promoting
spontaneous contractions that get
stronger and more frequent as the
pregnancy advances.
Distortion of Myometrium
Prostaglandin Production
Estrogens and oxytocin stimulate the production of
prostaglandins in the endometrium. These
prostaglandins further stimulate smooth muscle
contractions.
Maternal Oxytocin
Release
Maternal oxytocin release is
stimulated by high estrogen
levels and by distortion of the
cervix.
Increased Excitability of the Myometrium
Oxytocin and prostaglandins both stimulate the myometrium. In addition, the sensitivity of the uterus to
oxytocin increases dramatically; the smooth muscle in a late-term uterus is 100 times more sensitive to
oxytocin than the smooth muscle in a nonpregnant uterus.
LABOR CONTRACTIONS OCCUR
Labor contractions
move the fetus and
further distort the
myometrium. This
distortion stimulates
additional oxytocin
and prostaglandin
release. This positive
feedback continues
until delivery is
completed.

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

29-6 Labor
• Stages of Labor
1. Dilation stage
2. Expulsion stage
3. Placental stage

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)

Figure 29-11 The Stages of Labor
Fully developed fetus before labor begins
Placenta Umbilical
cord
Sacral
promontory
Cervical
canal
Cervix Vagina
Pubic
symphysis

The Dilation Stage

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

29-6 Labor
• Episiotomy
• Incision through perineal musculature
• Needed if vaginal canal is too small to pass fetus
• Repaired with sutures after delivery

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

The Expulsion Stage

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

The Placental Stage
Uterus 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

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

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

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

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

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

29-6 Labor
• Multiple Births
• Conjoined twins
• Siamese twins
• Genetically identical twins
• Occurs when splitting of blastomeres or of
embryonic disc is not completed

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

29-7 Postnatal Life
• Five Life Stages
1. Neonatal period
2. Infancy
3. Childhood
4. Adolescence
5. Maturity

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)

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

29-7 Postnatal Life
• The Neonatal Period
• Transition from fetus to neonate
• Neonate
• Newborn
• Systems begin functioning independently
• Respiratory
• Circulatory
• Digestive
• Urinary

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

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

Figure 29-12 The Milk Let-Down Reflex
Milk Ejected
Stimulation of Tactile Receptors
Start
Neural Impulse Transmission
Oxytocin Release
Posterior
lobe of the
pituitary
gland
Stimulation of Hypothalamic
Nuclei

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

Figure 29-13 Growth and Changes in Body Form and Proportion
Prenatal Development
Embryological Development Fetal Development
16 weeks
8 weeks
4 weeks

Figure 29-13 Growth and Changes in Body Form and Proportion
Postnatal Development
Neonatal Infancy Childhood Adolescence Maturity
1 month 2 years 18 yearsPuberty
(between 9–14 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

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

29-7 Postnatal Life
• Geriatrics
• Medical specialty dealing with problems
associated with aging
• Trained physicians, or geriatricians

29-7 Postnatal Life
• Effects of Aging on Organ Systems
• The characteristic physical and functional changes
that are part of the aging process affect all organ
systems
• Examples discussed in previous chapters include the
following:
• A loss of elasticity in the skin that produces sagging
and wrinkling (p. 164)
• A decline in the rate of bone deposition, leading to
weak bones, and degenerative changes in joints
that make them less mobile (pp. 192, 273)
• Reductions in muscular strength and ability (p. 368)

29-7 Postnatal Life
following:
• Impairment of coordination, memory, and intellectual
function (pp. 541–542)
• Reductions in the production of, and sensitivity to,
circulating hormones (p. 630)
• Appearance of cardiovascular problems and a
reduction in peripheral blood flow that can affect a
variety of vital organs (p. 758)
• Reduced sensitivity and responsiveness of the immune
system, leading to infection, cancer, or both (p. 806)

29-7 Postnatal Life
following:
• Reduced elasticity in the lungs, leading to decreased
respiratory function (p. 855)
• Decreased peristalsis and muscle tone along the digestive
tract (p. 909)
• Decreased peristalsis and muscle tone in the urinary
system, coupled with a reduction in the glomerular
filtration rate (p. 990)
• Functional impairment of the reproductive system, which
eventually becomes inactive when menopause or the
male climacteric occurs (p. 1069)

29-8 Inheritance
• Nucleated Somatic Cells
• Carry copies of original 46 chromosomes present in
zygote
• Genotype
• Chromosomes and their component genes
• Contain unique instructions that determine anatomical
and physiological characteristics
• Derived from genotypes of parents
• Phenotype
• Physical expression of genotype
• Anatomical and physiological characteristics

29-8 Inheritance
• Patterns of Inheritance
• Homologous chromosomes
• Members of each pair of chromosomes
• 23 pairs carried in every somatic cell
• At amphimixis, one member of each pair is
contributed by spermatozoon, other by ovum

29-8 Inheritance
• Autosomal chromosomes
• 22 pairs of homologous chromosomes
• Most affect somatic characteristics
• Each chromosome in pair has same structure and
carries genes that affect same traits

29-8 Inheritance
• Sex chromosomes
• Last pair of chromosomes
• Determine whether individual is genetically male or
female
• Karyotype
• Entire set of chromosomes
• Locus
• Gene’s position on chromosome

Figure 29-14 A Human Karyotype

29-8 Inheritance
• Alleles are various forms of given gene
• Alternate forms determine precise effect of gene on
phenotype
• Homozygous
• Both homologous chromosomes carry same allele of
particular gene
• Simple inheritance
• Phenotype determined by interactions between single
pair of alleles

29-8 Inheritance
• Interactions between Alleles
• Heterozygous
• Homologous chromosomes carry different allele of
particular gene
• Resulting phenotype depends on nature of interaction
between alleles
• Strict dominance
• Dominant allele expressed in phenotype, regardless of
conflicting instructions carried by other allele

29-8 Inheritance
• Interactions between Alleles
• Recessive allele
• Expressed in phenotype only if same allele is present
on both chromosomes of homologous pair
• Incomplete dominance
• Heterozygous alleles produce unique phenotype
• Codominance
• Exhibits both dominant and recessive phenotypes for
traits

Figure 29-15 Major Patterns of Inheritance
Major Patterns of Inheritance
Inheritance Involving
Autosomal Chromosomes
Simple Inheritance Polygenic Inheritance
The phenotype is determined by a
single pair of alleles; roughly 80% of
your genotype falls within this
category.
The phenotype is determined by
interactions among the alleles of
several genes.
Example:
• Hair color (other than blond or red,
which are recessive traits), skin color,
eye color, and height
Sex Chromosomes
X-linked inheritance:
The allele on the X
chromosome determines the
phenotype in the absence of a
corresponding allele on the Y
chromosome. Most known
cases involve alleles that are
recessive in females.
Examples:
• Red–green color blindness
• Hemophilia (some forms)
• Duchenne’s muscular
dystrophy

Figure 29-15 Major Patterns of Inheritance
Major Patterns of Inheritance
Strict Dominance Codominance Incomplete Dominance
Examples:
• Hemoglobin A
production
• Hemoglobin S
production
Two different alleles
produce intermediate
traits
Both alleles are
expressed
Examples:
• Type AB blood
• Structure of albumins
• Structure of
transferrins
Examples of
recessive traits:
• Albino pigmentation
• Absence of freckles
• Normal vision
• Straight hair
• Attached earlobes
• Inability to roll tongue
• Rh factor absence
• Type O blood
• Sickle cell anemia
• Cystic fibrosis
• Tay–Sachs disease
• Phenylketonuria
One allele dominates the other allele
and determines the phenotype
Examples of
dominant traits:
• Normal skin
pigmentation
• Freckles
• Nearsightedness
• Farsightedness
• Astigmatism
• Curly hair
• Free earlobes
• Tongue rolling
• Rh factor
• Type A or B blood
• Huntington’s disease
Autosomal Chromosomes

29-8 Inheritance
• Penetrance and Expressivity
• Penetrance
• Percentage of individuals with particular genotype
that show “expected” phenotype
• Expressivity
• Extent to which particular allele is expressed
• Teratogens
• Factors that result in abnormal development

29-8 Inheritance
• Predicting Inheritance
• Punnett square
• Simple box diagram used to predict characteristics
of offspring
• Polygenic inheritance
• Involves interactions among alleles on several genes
• Cannot predict phenotypic characteristics using Punnett
square
• Linked to risks of developing several important adult
disorders

Figure 29-16a Predicting Phenotypic Characters by Using Punnett Squares
Maternal alleles (contributed
by the ovum). Every ovum will
carry the recessive gene a.
Paternal alleles
(contributed by
the spermatozoon).
Every sperm
produced by a
homozygous
dominant (AA)
father will carry
the A allele.
All have normal skin
pigmentation
If the father is homozygous for normal pigmentation, all
of the children will have the genotype Aa, and all will
have normal skin pigmentation.

Figure 29-16b Predicting Phenotypic Characters by Using Punnett Squares
Half of the
sperm
produced by a
heterozygous (Aa)
father will carry the
dominant allele A,
and the other half
will carry the
recessive
allele a.
If the father is heterozygous for normal skin
pigmentation, the probability that a child will have
normal pigmentation is reduced to 50%.
Maternal
alleles
50% of the children are
heterozygous and have
normal pigmentation
50% of the children are
homozygous recessive and
exhibit albinism.

29-8 Inheritance
• Predicting Inheritance
• Suppression
• One gene suppresses other
• Second gene has no effect on phenotype
• Complementary gene action
• Dominant alleles on two genes interact to produce
phenotype different from that seen when one gene
contains recessive alleles

29-8 Inheritance
• Sources of Individual Variation
• During meiosis, maternal and paternal chromosomes
are randomly distributed
• Each gamete has unique combination of maternal
and paternal chromosomes

29-8 Inheritance
• Genetic Recombination
• During meiosis, various changes can occur in
chromosome structure, producing gametes with
chromosomes that differ from those of each parent
• Greatly increases range of possible variation among
gametes
• Can complicate tracing of inheritance of genetic
disorders

29-8 Inheritance
• Crossing over
• Parts of chromosomes become rearranged during
synapsis
• When tetrads form, adjacent chromatids may overlap
• Translocation
• Reshuffling process
• Chromatids may break, overlapping segments trade
places

Figure 29-17 Crossing Over and Recombination
Tetrad at
synapsis.
Synapsis, with
the formation
of a tetrad
during meiosis
Crossing over.
Crossing over of
portions of two
homologous
chromosomes
Recombination.
The exchange of
corresponding
segments and
groups of genes
increases
chromosomal
variation among
the gametes
produced.

29-8 Inheritance
• Genomic imprinting
• During recombination, portions of chromosomes may
break away and be deleted
• Effects depend on whether abnormal gamete is
produced through oogenesis or spermatogenesis

29-8 Inheritance
• Chromosomal abnormalities
• Damaged, broken, missing, or extra copies of
chromosomes
• Few survive to full term
• Produce variety of serious clinical conditions

29-8 Inheritance
• Mutation
• Changes in nucleotide sequence of allele
• Spontaneous mutations
• Result of random errors in DNA replication
• Errors relatively common, but in most cases error is detected
and repaired by enzymes in nucleus
• Errors that go undetected and unrepaired have potential to
change phenotype
• Can produce gametes that contain abnormal alleles
• Carriers
• Individuals who are heterozygous for abnormal allele
but do not show effects of mutation

29-8 Inheritance
• Sex-Linked Inheritance
• Sex Chromosomes
• X Chromosome
• Considerably larger than Y
• Has more genes than does Y chromosome
• Carried by all oocytes
• Y Chromosome
• Includes dominant alleles specifying that the
individual will be male
• Not present in females

29-8 Inheritance
• Sperm
• Carry either X or Y chromosome
• Because males have one of each, can pass along
either
• X-Linked
• Genes that affect somatic structures
• Carried by X chromosome
• Inheritance does not follow pattern of alleles on
autosomal chromosomes

Figure 29-18 Inheritance of an X-Linked Trait
A woman—who has two X
chromosomes—can be either
homozygous dominant (XC
XC
) or
heterozygous (XC
Xc
) and still
have normal color vision. She
will be unable to distinguish reds
from greens only if she carries
two recessive alleles, Xc
Xc
.
A man has
only one X
chomosome, so
whichever allele that
chromosome carries
determines whether he
has normal color
vision or is
red–green
color blind.
Normal female Normal female
(carrier)
Color blind
male
Normal male

29-8 Inheritance
• The Human Genome Project and Beyond
• Goal was to transcribe entire human genome
• Has mapped thousands of human genes
• Genome
• Full complement of genetic material
• Karyotyping
• Determination of individual’s complete chromosomal
complement

Figure 29-19 A Map of Human Chromosomes
Color Blindness (multiple forms) Chapter 17
Fragile-X Syndrome Chapter 29
Hemophilia
Chapter 19
Neurofibromatosis, Type 2
Tumors of the auditory nerves
and tissues surrounding the brain
Down’s Syndrome
Chapter 29
Amyotrophic Lateral Sclerosis*
Chapter 15
ADA Deficiency
An enzyme deficiency that
affects the immune system
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
Polycystic Kidney Disease
Chapter 26
Tay–Sachs Disease
Lysosomal storage disease
affecting neural tissue
Marfan’s Syndrome
Chapter 6
Alzheimer’s Disease*
Chapter 16
α1-Antitrypsin Deficiency
Causes a predisposition to
develop emphysema
Retinoblastoma
A relatively common tumor of the eye,
accounting for 2% of childhood malignancies
PKU
(phenylketonuria)
Chapter 25
Muscular Dystrophy Chapter 10
Prostate Cancer Chapter 28
Gaucher’s Disease
Lysosomal storage disease caused
by excess glycolipids in plasma membranes
Familial Colon Cancer*
Chapter 24
Retinitis Pigmentosa*
Chapter 17
Huntington’s Disease*
Chapter 17
Familial Polyposis of the Colon
Abnormal tissue growths that
commonly lead to colon cancer
Spinocerebellar Ataxia
Destroys neurons in the brain
and spinal cord, resulting in
loss of muscle control
Cystic Fibrosis
Chapter 23
Burkitt’s Lymphoma
Cancer of lymphocytes; a
type of non-Hodgkin lymphoma
Retinitis Pigmentosa*
Chapter 17
Epilepsy, progressive
Chapter 14
Malignant Melanoma
Chapter 5
Ovarian Cancer
Chapter 28
Multiple Endocrine Neoplasia, Type 2
Tumors in endocrine glands and
other tissues
SCID Chapter 22
Diabetes Mellitus, Type 1
Chapter 18
Sickle Cell Anemia Chapter 19
* One form of the disease
CHROMOSOME
PAIRS
XY 1 2
3
4
5
6
7
8
9
10
11121314
15
16
17
18
19
20
21
22

169 Ch 29_lecture_presentation

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Andere mochten auch

Andere mochten auch (12)

Ähnlich wie 169 Ch 29_lecture_presentation

Ähnlich wie 169 Ch 29_lecture_presentation (20)

Mehr von gwrandall

Mehr von gwrandall (14)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

169 Ch 29_lecture_presentation