1. Pregnancy & Human Development

3. Fertilization Oocyte viable 12-24 after ovulation
Sperm retain fertilizing power within female reproductive tract hours
Some “super sperm” viable for 72 hours
About 5 days a month that pregnancy can occur

4. 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

5. Capacitation
Membranes must become fragile so that hydrolytic enzymes in their acrosomes can be released

6. 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

7. Sperm Penetration Nucleus is pulled into oocyte cytoplasm
Only one sperm is allowed to penetrate
Fusion of nuclear material occurs to complete fertilization

8. Pre-embryonic Development
Fertilized egg is now called a zygote

9. 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

10. Cleavage & Blastocyst Formation
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

11. Implantation 6 days after ovulation implantation begins
Completed by 14 day

12. 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
Teratogens: may cause severe congenital abnormalities or even fetal death
Alcohol, nicotine, drugs, infections

13. 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
Yolk sac: blood cell formation & produce gonads
Chorion: forms placenta
Allantois: constructs umbilical cord
Becomes part of bladder

14. Gastrulation: Germ Layer Formation
Ectoderm
Mesoderm
Endoderm

15. Ectoderm All nervous tissue
Skin, hairs, sebaceous & sweat glands & nails
Tooth enamel
Epithelium of oral & nasal cavities, anal canal, pineal & pituitary glands

16. Mesoderm Skeletal, smooth & cardiac muscle Cartilage, bone & other CT
Blood, bone marrow, lymph tissue
Ureters, kidneys, gonads

17. Endoderm Epithelium of digestive tract Liver, pancreas
Thyroid, parathyroid & thymus glands

18. Effects of Pregnancy on Mother: 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 25lbs

19. Gastrointestinal System
Excessive salivation
Morning sickness: increase of hormones
Heartburn: esophagus & stomach is crowded
Constipation: motility of digestive tract declines

20. Urinary System Urination more frequent & sometimes uncontrollable
Uterus compresses bladder
Kidneys also have to dispose of fetal wastes

21. Respiratory System
Lung volume decreases
Nasal stuffiness

22. 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

23. Parturition
Birth 280 days after conception

24. 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

25. Stages of Labor: 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 minutes apart & last for sec.
Contractions become more vigorous & rapid
Infant’s head is forced against cervix causing it to soften & become thinner
Amniotic fluid breaks
Lasts 6-12 hours

26. 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

27. Placental Delivery of placenta within 15 minutes of birth
Important that all placental fragments be removed
Called afterbirth