1. PREGNANCY & HUMAN
DEVELOPMENT

2. Fertilization
oocyte viable 12 - 24 after ovulation
sperm retain fertilizing power within
female reproductive tract 12 - 48 hours
some “super sperm” viable for 72 hours
about 5 days a month that pregnancy
can occur

3. Sperm Transport
acidity within the vagina is hostile to
sperm & some leak from vagina or die
almost immediately
many cannot penetrate cervical mucus
in uterus thousands are killed by
leukocytes
only a few thousand finally reach
uterine tubes

4. Capacitation
membranes must become fragile so that
hydrolytic enzymes in their acrosomes
can be released

5. Acrosomal Reaction
acrosomal reaction: release of
acrosomal enzymes that occurs in
immediate vicinity of oocyte
hundreds of acrosomes must rupture to
break down intercellular cement of
oocyte
single sperm makes contact with oocyte

6. Sperm Penetration
nucleus is pulled into oocyte cytoplasm
only one sperm is allowed to penetrate
Fusion of nuclear material occurs to
complete fertilization

7. Preembryonic Development
fertilized egg is now called a
zygote

8. 1. Cleavage & Blastocyst
Formation
cleavage: period of rapid mitotic
divisions following fertilization
daughter cells become smaller &
smaller
results in a high surface-to-volume ratio
for greater uptake of oxygen &
nutrients

9. blastomeres:
– 2 identical cells by 36 hours
– 4 identical cells by 60 hours
– 8 identical cells by 72 hours
morula: berry-shaped
– 100 cell 4-5 days

10. Implantation
6 days after ovulation implantation
begins
completed by 14 day
1

11. Placentation
formation of placenta
highly vascular
fully functional as nutritive, respiratory,
excretory, & endocrine organ by end of
2nd month of pregnancy
some harmful substances can pass
placental barriers
1

12. teratogens: may cause severe
congenital abnormalities or even fetal
death
– alcohol, nicotine, drugs, infections
1

13. Events of Embryonic
Development
1

14. Formation & Roles of
Embryonic Membranes
amnion: sac that becomes filled with
amniotic fluid which bathes cells
– provides buoyant environment &
protection against physical trauma
– helps maintain temperature
– as kidneys develop urine is added to
fluid
– water portion is exchanged 3 hours
1

15. yolk sac: blood cell formation &
produce gonads
chorion: forms placenta
allantois: constructs umbilical cord
– becomes part of bladder
1

16. Gastrulation: Germ Layer
Formation
Ectoderm
Mesoderm
Endoderm
1

17. Ectoderm
all nervous tissue
skin, hairs, sebaceous & sweat glands,
& nails
tooth enamel
epithelium of: oral & nasal cavities,
anal canal, pineal & pituitary glands
1

18. Mesoderm
skeletal, smooth, & cardiac muscle
cartilage, bone & other CT
blood, bone marrow, lymph tissue
ureters, kidneys, gonads
1

19. Endoderm
epithelium of digestive tract
liver, pancreas
thyroid, parathyroid, & thymus glands
1

20. Effects of Pregnancy on
Mother
2

21. Anatomical Changes
breasts enlarge & areolae darken
“mask of pregnancy” pigmentation of
facial skin
uterus enlarges
lordosis
placenta produces the hormone relaxin,
that causes ligaments to relax & become
flexible for child birth
weight gain about 25 lbs
2

22. Gastrointestinal System
excessive salivation
morning sickness: increase of
hormones
heartburn: esophagus & stomach is
crowded
constipation: motility of digestive tract
declines
2

23. Urinary System
urination more frequent & sometimes
uncontrollable
uterus compresses bladder
kidneys also have to dispose of fetal
wastes
2

24. Respiratory System
lung volume decreases
nasal stuffiness
2

25. Cardiovascular System
total body water rises as safeguard
against blood lose during birth
blood volume increases 25 - 40 %
blood pressure & pulse rise
uterus presses on pelvic blood vessels,
venous return from lower limbs may be
impaired & result in varicose veins
2

26. Parturition
Birth 280 days after
conception
2

27. Initiation of Labor
last few weeks of pregnancy estrogen reaches
highest levels
myometrium becomes increasingly irritable &
weak which may cause Braxton Hicks
contractions or false labor
oxytocin is released by posterior pituitary
which causes expulsive contraction of true
labor
2

28. Stages of Labor
2

29. Dilation
time from labor’s onset until cervix is
fully dilated (10 cm)
contractions begin in upper part of
uterus & move downward toward
vagina
contractions 15 - 30 minutes apart & last
for 10 - 30 sec.
contractions become more vigorous &
rapid
2

30. infant’s head is forced against cervix
causing it to soften & become thinner
amniotic fluid breaks
lasts 6-12 hours
3

31. Expulsion
from full dilation to delivery
contraction every 2 - 3 minutes &
lasting 1 minute
lasts 20 minutes to 2 hours
crowning
episiotomy may be performed to reduce
tearing
umbilical cord is clamped & cut
3

32. Placental
delivery of placenta within 15 minutes
of birth
important that all placental fragments
be removed
called afterbirth
3