Transcript DrRonaldJSantangeloChapter29x

Chapter 29:1-5
Development and
Inheritance
Dr. Ronald J. Santangelo
MSHAPI-ITP
Final Project
Week 1
December 10, 2016
29:1 Development, various
stages, continuous process,
fertilization-maturity
• Learning Outcomes
• Explain relationship between differentiation
& development
• Specify various stages of development
Page 1096
• Development -gradual modification of
anatomical structures & physiological
characteristics from conception to maturity.
The formation of different types of cells is
differentiation.
• Prenatal development -occurs before birth:
postnatal development begins at birth to
maturity, when aging begins. Inheritance
transfer of genetically determined
characteristics from generation to generation.
Genetics is the study of mechanisms of
inheritance.
Check Point
• Define differentiation.
• What event marks the onset of
development?
• Define inheritance.
Review Video
29:2 Fertilization-secondary
oocyte & spermatozoon forms
zygote
• Learning Outcomes
• Describe the process of fertilization.
• Explain how developmental processes are
regulated
Page 1097
• Fertilization/ conception-normally in uterine
tubes within day after ovulation. Spermatozoa
can’t fertilize secondary oocyte until under
going capacitation
• Acrosomes of spermatozoa release
hyaluronidase & acrosin enzymes required for
corona radiate & zona pellucida penetration of
oocyte. Single spermatozoon contacts oocyte
membrane fertilization begins & oocyte
activation follows.
Figure 29-1b Fertilization (Part 1 of 6).
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
First polar
body
Figure 29-1b Fertilization (Part 2 of 6).
1 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
the completion of meiosis.
Second
Fertilizing
spermatozoon
polar
body
Figure 29-1b Fertilization (Part 3 of 6).
2
Pronucleus Formation Begins
The sperm is absorbed into the
cytoplasm, and the female
pronucleus develops.
Nucleus of
fertilizing
spermatozoon
Female
pronucleus
Page 1097
• During activation oocyte completes meiosis II
becoming functional mature ovum.
Polyspermy prevented by membrane
depolarization & the cortical reaction.
• After activation, female pronucleus & male
pronucleus fuse in process called
amphimixis
Figure 29-1b Fertilization (Part 4 of 6).
3
Spindle Formation and
Cleavage Preparation
The male pronucleus develops, and
spindle fibers appear in preparation
for the first cleavage division.
Male
pronucleus
Female
pronucleus
Figure 29-1b Fertilization (Part 5 of 6).
4
Amphimixis Occurs and
Cleavage Begins-zygote
46 chromosomes
Metaphase of first
cleavage division
Figure 29-1b Fertilization (Part 6 of 6).
5
Cleavage Begins
The first cleavage division nears
completion about 30 hours after
fertilization.
Blastomeres
Check Point
• Name two sperm enzymes important to
secondary oocyte penetration.
• How many chromosomes are contained
within a human zygote?
Review Video
29:3 Gestation 3 stages
prenatal development
• Learning Outcomes
• List the 3 stages of prenatal development
• Describe the major events in each stage
3 stages of prenatal
development
• 1st Trimester -period of embryonic & early
fetal development, major organs appear
• 2nd Trimester –dominated by organs and
organ system development, near completion
by end of month 6, body shape & proportions
change, looks distinctively human
• 3rd Trimester –rapid fetal growth & adipose
deposition early 3rd major organs fully
functional, 1 or 2 months premature birth has
reasonable survival rate
Check Point
• Define gestation.
• Characterize key features of each
trimester/ stage of fetal development.
Review Video
29:4 Cleavage, implantation
& embryogenesis critical
st
events in 1 trimester
• Learning Outcomes
• Explain how 3 germ layers are involved in
forming the embryonic membranes.
• Discuss the importance of the placenta as
an endocrine organ.
1st Trimester
• Cleavage - zygote becomes pre-embryonic
develops into blastocyst (multicellular
complex), ends with contact of uterine wall
• Implantation –begins with blastocyst
attachment to endometrium, invade maternal
tissue, stages formation of vital embryonic
structures
• Placentation -formation of blood vessels
around blastocyst. Placenta organ permitting
change between maternal and embryonic
blood. Forms, supports & expelled from uterus
• Embryogenesis –vital embryo formation,
establishes foundation for all major organ
systems
Blastomeres form blastocyst a hollow ball w/ inner cavity know as
blastocoele
Polar
bodies
2-cell stage
DAY 1
First cleavage
division
DAY 0:
Fertilization
Figure 29-2 Cleavage and Blastocyst Formation (Part 1 of 2).
4-cell stage
DAY 2
Figure 29-2 Cleavage and Blastocyst Formation (Part 2 of 2).
Zona
pellucida
Early morula
DAY 3
Days 7–10:
Implantation in
uterine wall
(see Figure 29–3)
Advanced
DAY 4
morula
Hatching
Inner cell
mass
DAY 6
Blastocoele
Trophoblast
Blastocyst
Figure 29-3 Stages in Implantation (Part 1 of 2).
DAY 6 FUNCTIONAL ZONE
OF ENDOMETRIUM
Uterine
glands
DAY 7
post fertilization
Blastocyst adheres
to uterine lining
UTERINE
CAVITY
Blastocyst
Trophoblast
Blastocoele
Inner cell
mass
DAY 8 plasma membrane separates, trophoblast
disappear creates cytoplasm
Endometrial
capillary
Cellular
trophoblast
Syncytial
DAY 9
trophoblast
Outer layer Developing villi
hyaluronidase
erodes uterine
epithelium dissolves
proteoglycans
Figure 29-3 Stages in Implantation (Part 2 of 2).
Amniotic
cavity
Lacuna
Figure 29-3 Stages in Implantation (Part 2 of 2).
Endometrial capillary
DAY 8
Syncytial
trophoblast
Cellular
trophoblast
DAY 9
Developing villi
Amniotic
cavity
Lacuna
Figure 29-4 The Inner Cell Mass and Gastrulation (Part 1 of 2).
Syncytial trophoblast
Day 10: Yolk Sac Formation
Superficial layer
Deep layer
Cellular
trophoblast
Blastocoele
Amniotic
cavity
Yolk sac
Lacunae
While cells from the superficial layer of the inner cell mass
migrate around the amniotic cavity, forming the amnion, cells
from the deeper layer migrate around the outer edges
of the blastocoele. This is the first step in the formation of the
yolk sac, a second extraembryonic membrane. For about the
next two weeks, the yolk sac is the primary nutrient source for
the inner cell mass;it absorbs and distributes nutrients released
into the blastocoele by the trophoblast.
Figure 29-4 The Inner Cell Mass and Gastrulation (Part 2 of 2).
Day 12: Gastrulation
Yolk sac
Ectoderm
Germ
Layers
Amnion
Primitive streak
Endoderm
Mesoderm
Embryonic
disc
Blastodisc
Day 12, superficial cells of blastodisc
migrate toward a central line(primitive streak). At primitive
streak, migrating cells leave surface, move between two
existing layers. Creating 3 distinct embryonic layers: (1) the
ectoderm, superficial cells that didn’t migrate
to interior blastodisc; (2) the endoderm, cells facing yolk
sac; (3) the mesoderm, poorly organized layer of migrating
cells between ectoderm and endoderm.
Germ layers form 4
Embryonic Membranes
• Yolk sac-important blood cell formation site
• Amnion-encloses fluid surrounding&
cushioning developing embryo
• Allantois-base gives rise to urinary bladder
• Chorion-circulation w/in vessels provides
rapid-transfer system linking embryo to
trophoblast
Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 3 of 7).
1
Week 2
Migration of mesoderm around the inner surface of the cellular
trophoblast forms 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.
Chorion
Mesoderm Cellular trophoblast Amnion
Blastocoele
Yolk sac
Syncytial
trophoblast
Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 4 of 7).
2
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)
Head fold
of embryo
Chorionic villi
of placenta
Extraembryonic
membranes
Amnion
Allantois
Yolk sac
Chorion
Syncytial trophoblast
Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 5 of 7).
3
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 yolkstalk and body stalk.
Body stalk
Tail fold
Yolksac
Yolk stalk
Embryonic gut
Embryonic
head fold
Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 6 of 7).
Week 5
The developing embryo and extraembryonic membranes
bulge into the uterine cavity. The trophoblast pushing out
into the uterine cavity 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.
4
Decidua
basalis
Myometrium
Uterus
Uterine
cavity
Umbilical
stalk
Placenta
Yolk sac
Chorionic villi of
placenta
Decidua
capsularis
Decidua
parietalis
Figure 29-5 Extraembryonic Membranes and Placenta Formation (Part 7 of 7).
5
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.
Decidua basalis
Umbilical cord
Placenta
Decidua parietalis
Amnion
Decidua capsularis
Amniotic cavity
Chorion
Figure 29-6
• Chorionic villi-extend outward into maternal
tissue, forming branching network, maternal
blood flows
• Umbilical- connects fetus to placenta
• Syncytial trophoblast- synthesize hCG,
estrogen, progesterone, human placental
lactogen(hPL), placental prolactin, relaxin
Figure 29-6a Views of Placental Structures (Part 1 of 3).
Decidua
capsularis
Amnion
Umbilical
cord (cut)
Placenta
Chorion
Yolk sac
Decidua
basalis
a
A view of the uterus after the fetus has been removed and the
umbilical cord cut. Arrows in the enlarged view indicate the
direction of blood flow. Blood flows into the placenta through
ruptured maternal arteries and then flows around chorionic
villi, which contain fetal blood vessels.
Figure 29-6a Views of Placental Structures (Part 2 of 3).
Deciduaparietalis
Myometrium
Uterine cavity
Cervical(mucous)
plug incervical canal
Cervix
External os
Vagina
a A view of the uterus after the fetus has been
removed and the umbilical cord cut. Arrows in
the enlarged view indicate the direction of blood
flow. Blood flows into the placenta through
ruptured maternal arteries and then flows around
chorionic villi, which contain fetal blood vessels.
Figure 29-6a Views of Placental Structures (Part 3 of 3).
Chorionic
villi
Umbilical
vein
Umbilical
arteries
Area filled with
maternal blood
Amnion
Trophoblast (cellular
and syncytial layers)
Maternal
blood vessels
a A view of the uterus after the fetus has been removed and
the umbilical cord cut. Arrows in the enlarged view indicate
the direction of blood flow. Blood flows into the placenta
through ruptured maternal arteries and then flows around
chorionic villi, which contain fetal blood vessels.
Figure 29-6b Views of Placental Structures.
Syncytial
trophoblast
Embryonic
connective tissue
Area filled with
maternal blood
Fetal blood
vessels
Chorionic villus
b
LM × 280
A cross section through a chorionic
villus, showing the syncytial trophoblast
exposed to the maternal blood space.
The First 12 Weeks of Development. Vital for organogenesis
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
a 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.
Medulla
oblongata
Ear
Pharyngeal
arches
Forebrain
Eye
Heart
Somites
Body stalk
Arm bud
Tail
Leg bud
b Week 4. Fiber-optic view of human development
at week 4 (about 5 mm in size).
Figure 29-7c The First 12 Weeks of Development.
Chorionic
villi
Amnion
Umbilical
cord
Placenta
c Week 8. Fiber-optic view of human
development at week 8 (about 1.6 cm in size).
Figure 29-7d The First 12 Weeks of Development.
Amnion
Umbilical
cord
d Week 12. Fiber-optic view of human development
at week 12 (about 5.4 cm in size).
Check Point
• What is the developmental fate of the inner cell
mass of blastocyst?
• Improper development of which of the
extraembryonic membranes would affect the
cardiovascular system?
• Sue’s pregnancy test indicates the presence of
hCG. Explain whether she is pregnant or not.
• What are two important functions of the
placent?
Review Video
29-5 During 2nd & 3rd trimester
maternal organ systems support
fetus & uterus undergoes
structural & functional changes
• Learning Outcomes
• Describe interplay between maternal organ
systems & developing fetus.
• Discus structural & functional changes in the uterus
during gestation.
Figure 29-8a
2nd Trimester
organ systems
increase in
complexity
3rd Trimester
many organs
fully functional,
Largest weight
gain, fetus &
enlarged uterus
displace
abdominal
organs
a
A four-month-old fetus, seen
through a fiber-optic endoscope
(about 13.3 cm in size)
Figure 29-8b The Second
and
Third Trimestersdependent on maternal
organs for nourishment,
respiration, waste removal.
Maternal adaptationsincrease respiratory rate,
tidal volume, blood volume,
nutrient/vitamin intake,
GFR, changes in uterus &
mammary glands
Head of a six-monthb old fetus, revealed
through ultrasound
(about 30 cm in size)
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
a 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
4 months
3 months
After dropping,
in preparation
to delivery
b Pregnancy at three months to nine months (full term), showing
the superior-most position of the uterus within the abdomen.
Figure 29-9c Growth of the Uterus and Fetus.
Diaphragm
Liver
Stomach
Pancreas
Transverse colon
Small intestine
Uterus
Urinary bladder
Pubic symphysis
Vagina
Urethra
Rectum
c
A sectional view through the abdominopelvic
cavity of a woman who is not pregnant.
Figure 29-9d Growth of the Uterus and Fetus.
Liver
Fundus
Stomach
of uterus
Pancreas
Aorta
Transverse colon
Small intestine
Common
Umbilical cord
Placenta
Uterus
iliac vein
Cervical (mucous)
plug in
cervical canal
Urinary bladder
Pubic symphysis
Vagina
Urethra
Rectum
External os
d
Full term. Note the positions of the uterus and full-term fetus
within the abdomen, and the displacement of abdominal organs.
Factors Involved in the Initiation of Labor and Delivery.
Placental Factors
Fetal Factors
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.
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 Stretched Myometrium
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.
Maternal Oxytocin Release
Prostaglandin Production
Maternal oxytocin release is
stimulated by high estrogen levels
and by distortion of the cervix.
Estrogens and oxytocin stimulate the production of
prostaglandins in the endometrium. These prostaglandins
further stimulate smooth muscle contractions.
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.
Check Point
• Why do woman experience breathing difficulty?
• Identify 3 major factors opposing calming
action of progesterone on the uterus.
• Why do mother blood volume increase during
pregnancy?
• Differentiate between true and false labor.
Review Video
• Second trimester.
https://www.youtube.com/watch?v=VEH2evJpVg
• Third trimester.
https://www.youtube.com/watch?v=qTpXaRYPGK
M
References
• Martini, Nath & Bartholomew (2105), Fundamentals
of Anatomy and Physiology (10th ed.).
• You Tube
https://www.youtube.com/watch?v=bHYAMjwgeV8
• https://www.youtube.com/watch?v=7G2rL5Cutd4
• https://www.youtube.com/watch?v=zasjMiQjvr0
• https://www.youtube.com/watch?v=UgT5rUQ9EmQ
• https://www.youtube.com/watch?v=VEH2evJpVg
• https://www.youtube.com/watch?v=qTpXaRYPGKM