1. Chapter 23: Pregnancy, Growth & Development
Pregnancy is the presence of a developing offspring in the uterus
Growth is an increase in size and entails increases in cell numbers and cell sizes
Development is the continuous process by which an individual changes from one life phase to another and involves two phases
Prenatal period – fertilization to birth
Postnatal period – birth to death

2. Pregnancy Fertilization (aka conception) Union of egg and sperm cells
Occurs in the Fallopian tube
Journey from cervix to uterine tube takes less than an hour
Oocyte survives only hrs after ovulation
Sperm may live hrs within female
Page 895:
morning sickness
Page :
ARTs

3. Period Of Cleavage & Implantation
The first division of the zygote (fertilized egg) will occur about 30 hours after fertilization.
Division continues as the zygote moves down toward the uterus.
Implantation in the uterus occurs about 6-7 days after fertilization
Period Of Cleavage & Implantation

4. Fertilization sperm cell reaches corona radiata of egg
acrosome releases enzymes
sperm cell penetrates zona pellucida
sperm cell’s membrane fuses with egg cell’s membrane

5. Implantation
Blastocyst secretes enzyme that digests the endometrium allowing it to bury into the uterine wall
Layer of cells called trophoblast helps form the placenta and secretes hCG which helps maintain the corpus luteum and thus the pregnancy

6. Page 900: Twins
Page 901: Ectopic Pregnancy
Page : Preimplantation Genetic Diagnosis
Page 903: Hormonal Testing
Pregnancy tests test
for the presence of hCG

7. Hormonal Changes During Pregnancy
Main hormonal secretions:
secretion of hCG maintains corpus luteum
corpus luteum secretes estrogens and progesterone
placenta secretes large amounts of estrogens and progesterone which stimulate and maintain uterine lining, inhibit FSH and LH, inhibit uterine contractions, and enlarge reproductive organs
Additional hormonal secretions:
relaxin from corpus luteum inhibits uterine contractions and relaxes pelvic ligaments
placental lactogen stimulates breast development
aldosterone promotes sodium retention
PTH maintains calcium concentrations in blood

8. Embryonic Stage Beginning of the 2nd week through the 8th week
Heart begins to beat during 5th week
Beginning of the 2nd week through the 8th week

9. Placenta Embryonic Testing may include Chorionic Villus Sampling
Reddish brown disc
Approximately 20 cm long and 2.5 cm thick
Connection between embryo and uterine wall
Chorion is embyonic portion of placenta
Embryonic Testing may include Chorionic Villus Sampling

10. Amnion
About the 2nd week a membrane called the amnion develops around the embryo
Fluid called the amnionic fluid fills the area between the embryo and amnion

11. Ammniocentesis 15-20 wks Approximately 2 Tbsp (30 mL) fluid removed
Used to determine genetic abnormalities

12. Umbilical Cord The umbilical cord forms from the amnion and chorion
Is about 55 cm long and 1 cm in diameter
Inserts into center of placenta and connects to abdomin of embryo
Contains 2 arteries and 1 vein
Transports blood between embryo and placenta

13. Summary Of Embryonic Period
Most critical period of development
All major organs are formed
About 30 mm long and weighs about 5 g
Time during which teratogens (drugs, viruses, radiation, etc..) are most likely to cause birth defects

14. Teratogens & Embryonic Developement

15. Thalidomide

16. Fetal Stage 9th week until birth
Rapid growth; head becomes more proportional to rest of body
Bones begin to ossify
Mother feels 1st fetal movements around 5th month (once called quickening)
Fine downy hair called lanugo covers body
Vernix caseosa covers body – mix of sebum and epidermal cells – protects skin from amniotic fluid
Nervous & Circulatory systems 1st to develop during embryonic period and Digestive & Respiratory systems are last to develop during fetal period.
Premature babies often have respiratory difficulties because their lungs are not yet producing surfactant

17. Trimesters
Pregnancy is divided into 3 distinct time periods called trimesters
Each trimester is 3 months in length.
1st trimester – embryonic period and beginning of fetal stage – Rapid development of organ systems
2nd trimester – middle of fetal period – adding details to organ systems
3rd trimester – end of pregnancy – adding fat

18. Fetal Blood And Circulation
oxygen and nutrients diffuse into the fetal blood from the maternal blood
waste diffuses into the maternal blood from the fetal blood
Fetal blood and maternal blood DO NOT mix

19. Fetal Cardiovascular Adaptations
fetal blood has greater oxygen-carrying capacity
umbilical vein carries oxygenated blood from placenta to fetus
ductus venosus conducts half the blood from umbilical vein to inferior vena cava; liver is bypassed
foramen ovale conveys blood from right atrium to left atrium; lungs are bypassed
ductus arteriosis conducts some blood from pulmonary trunk to aorta; lungs are bypassed
umbilical arteries carry blood from internal iliac arteries to placenta

20. Position Of Full-term Fetus
Fetal position before labor is head down toward cervix facing the spine
Breech babies are positioned with buttocks downward toward cervix
Position Of Full-term Fetus

21. Birth Process Also called Parturition Involves two stages: Labor –
Events that occur in preparation for delivery of the fetus
Cervical changes & uterine contractions
Delivery – the actual expulsion of the fetus & placenta from the body

22. Birth Process Factors contributing to the labor process:
as birth approaches, progesterone levels decrease
prostaglandins synthesized which may initiate labor
stretching uterine tissue stimulates release of oxytocin from posterior pituitary gland (pitocin is a synthetic form of oxytocin and is used to induce labor)
oxytocin stimulates uterine contractions
fetal head stretches uterus
positive feedback results in stronger and stronger contractions and greater release of oxytocin

23. Stages In Birth - Labor
Baby is in head down position and is occupying the lower part of the womb – “baby has dropped”
“false labor” may occur

24. Stages In Birth - Labor Thinning & dilation of the cervix
May begin a week or two before actual birth
Thinning of cervix referred to as effacement
Cervix will dilate to 10 cm.
Muscle contractions of uterus occur
Amnion ruptures (“water breaks”)

25. Stages In Birth - Delivery
Contractions intensify and fetus is expelled
Episiotomy may be performed to aid in delivery of fetus
Expulsion of the placenta - afterbirth

26. Cesarean Birth
Conjoined twins as shown on page 921 would need to be born through cesarean birth.

27. Postnatal Developement
Neonatal period – birth to 4th week
Infancy – 4th week to one year
Childhood – one year to puberty
Adolescence – puberty to adulthood
Adulthood – adolescence to old age
Senescence – old age to death