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Eggs are giant cells
Egg coat
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Mammals = Zona pellucida AND cumulus cells
Polar
body
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Capacitation of sperm
Spermatozoa reach uterine tube within 10 minutes
of ejaculation
To fertilize ovum, they must undergo capacitation
 takes 10 hours
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Sperm fertile for 48 hours after ejaculation
Conception optimal if sperm are deposited 48 hours
before ovulation to 14 hours after
28-2
• Binding to ZP3 induces the acrosome reaction.
• Proteolytic enzymes released by the acrosome
digest a hole through the zona pellucida
Fig. 29.2
29-4
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The blastula has a trophoblast and ICM
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Attaches to uterine wall 6 to 12 days after ovulation
Syncytiotrophoblast - multinucleate mass grows “roots”
and digests its way into endometrium
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secretes human chorionic gonadotropin (HCG)
becomes chorion
Endometrium completely encloses embryo
29-6
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Mammals have the same gastrulation movements
as reptiles and birds even though there is no yolk
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Arrangement of blastomeres
into 3 primary germ layers
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Ectoderm
Mesoderm
Endoderm
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Flattening of embryoblast into
embryonic disc
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Cells sink into primitive streak (a groove) and spread
laterally as mesoderm layer
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as mesenchyme cells
29-8
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Formation of organs from primary germ layers
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Derivatives of ectoderm
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epidermis, nervous system, lens and cornea, internal ear
Derivatives of mesoderm
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at 8 weeks, all organs are present in 3 cm long fetus
heart is beating and muscles exhibit contracts
skeleton, muscle, cartilage, blood, blood vessels, lymphoid
tissue, gonads and ducts, kidneys and ureters
Derivatives of endoderm
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gut and respiratory epithelium, liver, bladder and urethra
29-9
29-10
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HCG (human chorionic gonadotropin)
secreted by trophoblast within 9 days of conception
 prevents involution of corpus luteum
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Estrogens
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increases to 30 times normal before birth
corpus luteum is source for first 12 weeks until placenta
takes over
causes uterine, mammary duct and breast enlargement
Progesterone
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secreted by placenta and corpus luteum
suppresses secretion of FSH and LH preventing follicular
development
prevents menstruation, thickens endometrium
stimulates development of acini in breast
28-11
28-12
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Blastocyst implants outside uterus
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1 out of 300 pregnancies
most cases occur in uterine tube (tubal pregnancy)
 tubal obstruction from previous pelvic inflammations increase risk
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Tube ruptures by 12 weeks
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conceptus may reimplant in abdominopelvic cavity
 anywhere it finds an adequate blood supply
 usually requires an abortion
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9% of abdominal pregnancies result in live birth by cesarean
section
29-13
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Trophoblastic nutrition - conceptus nourished by
digestion of endometrial cells (first 8 weeks)
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progesterone stimulates decidual cells of uterus
Placental nutrition - conceptus nourished from
mother’s bloodstream through placenta
29-14
The placenta is an
organ derived from
both maternal and
fetal-derived tissues.
29-15
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Age based terminology
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Blastocyst is less than 2 weeks old
Embryo is from 2 to 8 weeks old
 Three embryonic tissue layers have formed
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Fetus is 9 weeks to birth
 Organs have begun to form
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Neonate - newborn to 6 weeks
28-16
28-17
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Progesterone inhibits contractions
Estrogen stimulates contractions
Near full term - posterior pituitary releases more
oxytocin, uterus produces more receptors
directly stimulates myometrial contractions
 stimulates fetal membranes to produce prostaglandins synergists of oxytocin
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Stretching
increases contractility of smooth muscle
 role in initiating labor
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28-18
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Contractions begin 30 minutes apart and eventually
occur every 1-3 minutes
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periodically relax to  blood flow to placenta and fetus
contractions strongest in fundus and body of uterus,
pushes fetus into cervix
Self-amplifying cycle of stretch and contraction
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positive feedback cycles increase contractions
 cervical stretching  oxytocin secretion  uterine
contraction  repeat
 reflex arc from uterus  spinal cord  abdominal
skeletal muscles
28-19
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Widening of cervical canal by effacement (thinning) of cervix to
reach 10 cm -- diameter of fetal head
Rupture of fetal membranes and loss of amniotic fluid
28-20
Dilation reaches 10 cm in 24 hours or less in primipara (first baby)
and in as little as few minutes in multipara
28-21
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Time baby’s head enters vagina until delivery
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up to 30 minutes
Valsalva maneuver helps to expel fetus
28-22
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Uterine contractions continue causing placental separation
28-23
28-24
28-25
28-26
Ductus venosus
Ductus arteriosus
Foramen ovale
29-27
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Umbilical
arteries and
veins become
ligamentous
Ligamentum
venosum
(liver)
Fossa ovalis
(heart)
Ligamentum
arteriosum
(vessels)
29-28
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Transitional period
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Respiratory adaptations of newborn
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first 6-8 hours heart and respiratory rate  and body
temperature falls
periods of sleeping and gagging on mucus and debris
feed every 3 to 4 hours during 6 week neonatal period
onset of breathing due to CO2 accumulation
great effort to inflate lungs for first few breaths
Immunological adaptation
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maternal antibody, IgG, diffuses across placenta
 provides 6 mo of protection from most infectious diseases while
fetal production 
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IgA in breast milk can protect newborn from
gastroenteritis
29-29
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Colostrum forms in late pregnancy
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Controlled by a
neuroendocrine reflex
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similar to breast milk; contains 1/3 less fat, thinner
first 1 to 3 days after birth
contains IgA protection from gastroenteritis
infant’s suckling stimulates
sensory receptors in nipple,
signaling hypothalamus and
posterior pituitary to release
oxytocin
oxytocin stimulates myoepithelial
cells
Myoepithelial cells surround
secretory cells in acinus
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contract to squeeze milk into duct
milk flow within 30-60 seconds
after suckling begins
28-30
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First 6 weeks after delivery
Anatomy and physiology return to normal

involution of uterus
 to pre-gravid weight in 4 weeks
 accomplished by autolysis by lysosomal enzymes
 vaginal discharge called lochia
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breastfeeding promotes involution
 suppresses estrogen secretion
 stimulates oxytocin which causes myometrial contraction
28-31
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Midlife change in hormone secretion
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Results
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due to age related depletion of follicles
occurs with menopause (cessation of menstruation);
average age of 52
atrophy of uterus, vagina and breasts
skin becomes thinner, bone mass declines, and risks of
cardiovascular disease increase
hot flashes (sudden dilation of cutaneous arteries) occur
several times a day
HRT = hormone replacement therapy
28-32
28-33
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Digestive System
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nausea
 first few months
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constipation and heartburn due to
  intestinal motility
 pressure on stomach
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Metabolism
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BMR  may stimulate appetite
 healthy weight gain - 24 lb.
28-34
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Nutrition
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placenta stores nutrients for 3rd trimester
 protein, iron, calcium, phosphates
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vitamin K
 reduces risk of hemorrhages in neonatal brain
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folic acid
 prevent neurological disorders
 spina bifida, anencephaly
 supplements must be started before pregnancy
28-35
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Circulatory System
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mother’s blood volume and cardiac output - rises 30%
 due to fluid retention and hemopoiesis
 by full term, placenta requires 625 mL of blood/minute
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hemorrhoids and varicose veins
 from pressure on large pelvic blood vessels
28-36
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Respiratory System
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minute ventilation  about 50%
 demands of fetus, higher maternal metabolic rate
 ventilation adjusted to keep PCO2 lower than normal
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respiratory rate 
 difficult to breathe deeply
28-37
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Urinary System
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salt and water retention
 due to aldosterone and steroids
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GFR  by 50% and output is slightly elevated
 mother disposes additional metabolic wastes
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 frequency of urination
 due to bladder compression
28-38
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Integumentary Systems
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stretch marks
 due to dermal stretching
linea alba may become dark (linea nigra)
 temporary chloasma or “mask of pregnancy”
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 blotchy darkening of skin over nose and cheeks
28-39
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Parturition
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process of giving birth
 by contraction of uterine and abdominal muscles
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Braxton Hicks contractions
throughout gestation
 strengthen late in pregnancy - false labor
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28-40
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Ischemia of myometrium
Stretching of cervix, vagina and perineum
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episiotomy prevents tearing
Large fetal head in a narrow pelvic outlet
28-41
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Lactation
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Ducts grow and branch
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synthesis and ejection of milk from mammary glands in breast
due to high estrogen levels in pregnancy
Followed by budding and development of acini at the
ends of the ducts
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due to progesterone
28-42
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Colostrum forms in late pregnancy
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similar to breast milk; contains 1/3 less fat, thinner
first 1 to 3 days after birth
contains IgA protection from gastroenteritis
Synthesis is promoted by prolactin (from pituitary)
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synthesis of hormone begins 5 weeks into pregnancy, by full
term it is 20x normal level
steroid hormones from placenta oppose it until birth
28-43
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At birth, prolactin secretion drops, but 
20 times after nursing
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without nursing, milk production stops in 1 week
5-10% of women become pregnant while nursing
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inhibition of GnRH and reduced ovarian cycling
28-44
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Controlled by a neuroendocrine reflex



infant’s suckling stimulates sensory receptors in nipple,
signaling hypothalamus and posterior pituitary to release
oxytocin
oxytocin stimulates myoepithelial cells
Myoepithelial cells surround secretory cells in acinus

contract to squeeze milk into duct
 milk flow within 30-60 seconds after suckling begins
28-45
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Supplies antibodies and colonizes intestine with
beneficial bacteria
Colostrum and milk have a laxative effect that clears
intestine of meconium (green, bile-filled fecal material in
newborn)
Nursing woman can produce 1.5L per day
Cow’s milk not a good substitute
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1/3 less lactose but 3 times as much protein
harder to digest and more nitrogenous waste (diaper rash)
28-46
28-47
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1 out of 8 American women
Tumors begin with cells from mammary ducts
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Symptoms may include palpable lump, skin puckering,
skin texture and drainage from nipple
Most breast cancer is nonhereditary
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may metastasize by lymphatics
some stimulated by estrogen
Risk factors include
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aging, ionizing radiation, carcinogenic chemicals, alcohol,
smoking and fat intake
70% lack risk factors
28-48
28-49
28-50