Transcript Pregnancy and Embryonic Development Notes

Welcome to Baby
Making 101
III. Pregnancy and Embryonic
Development
A. Accomplishing Fertilization
1. oocyte viable for 12-24
hours after ovulation
2. sperm is viable for 12-48
(sometimes up to 72) hours
after ejaculation. Takes 1-2
hours to swim length of
fallopian tubes
3. fertilization – moment genetic
material of sperm combines
with genetic material of ovum
to form zygote
a. in order to achieve
fertilization, sex may occur
no more than 72 hours before
ovulation and no more than
24 hours later.
b. generally occurs in upper
1/3 of fallopian tubes
c. requires several sperm to
“clear a path” through
corona radiata
B. Events of Embryonic and Fetal
Development
1. after 3 days of cell division
(cleavage) zygote is now a
morula (solid ball of 16 cells)
2. continued divisions result in
blastocyst (hollow ball)
which implants itself in the
uterine wall 10 days after
fertilization
3. blastocyst secretes HCG (Human
Chorionic Gonadotropin) causing
the corpus luteum to produce
progesterone, which in turn
maintains uterine lining
4. three germ layers have now
formed (day 7)
a. ectoderm – gives rise to nervous
system and epidermis
b. mesoderm – everything in
between
c. endoderm – mucosae and
associated glands
5. by day 14 implantation is
complete and uterine mucosa
has grown over embryo
6. blastocyst develops
projections (chorionic villi)
together with mother’s tissue
make up the placenta
7. embryo surrounded by
amnion and is attached to
placenta by the umbilical
cord (functional during
third week)
8. by
a.
b.
c.
week eight:
all systems developing
embryo looks human
umbilical cord producing
estrogen and progesterone to
maintain uterine lining;
corpus luteum becomes
inactive
9. by week nine:
a. embryo now referred to as
fetus
b. major activities are growth,
organ specialization, and
developing body proportions
10. “Fetal Development Period” –
from 9th week on
a. growth from 1 to 14 inches
(crown to rump)
b. weight gain from .03 ounces
to 6-10 pounds
c. at birth total body length
(head to foot) is about 22
inches
11. fetus is “full term” 270 days
after fertilization – the end of
the 10th lunar month
C. Effects of Pregnancy on the
Mother
1. Anatomical changes
a. growth of uterus
1. pushes into abdominal
cavity
2. by birth has reached
level of xiphoid process
3. causes abdominal organs
to press superiorly against
diaphragm; ribs flare and
thorax widens
b. center of gravity change can
bring on lordosis and
accompanying backaches
c. placental production of relaxin
causes pelvic ligaments and
pubic symphysis to relax and
widen, causing waddling gait
d. substances to avoid include
alcohol (FAS), nicotine,
anticoagulants,
antihypertensives, sedatives,
some antibiotics; German
measles (rubella virus) can also
cause severe fetal damage
2. Physiological changes
a. gastrointestinal system
1. morning sickness due
to elevated hormone
levels
2. heartburn
3. constipation
b. urinary system
1. increased urine
production
2. frequent, urgent, and
uncontrollable
c. respiratory system
1. nasals stuffiness and nose
bleeds – estrogen’s effect
on nasal mucosa
2. breathing becomes difficult
and respiratory rate
increases
d. cardiovascular system
1. blood volume increases
25-40%
2. BP and pulse increase
3. varicose veins may develop
D. Childbirth (parturition) – within
15 days of due date, 280 days
from last menstrual period
1. initiation of labor
a. estrogen levels increase
last few weeks
1. myometrium becomes
sensitive to oxytocin
2. oxytocin interferes with
progesterone’s quieting
effect on uterine muscle;
can cause Braxton Hicks
contractions or false
labor
b. fetal cells producing
oxytocin and the placenta
releasing prostaglandins
stimulate powerful
contractions
c. mother’s physical and
emotional stress stimulates
the hypothalamus which in
turn stimulates the posterior
pituitary to increase oxytocin
production
d. increased oxytocin combined
with prostaglandins initiates
true labor
e. positive feedback loop
established between
contractions and oxytocin
f. Aspirin/ibuprofen inhibit
release of prostaglandins in
early stages of labor; may
be used to prevent
premature births
2. stages of labor
a. stage 1: Dilation – from
start of true contractions
until full cervix dilation
(10 cm)
1. longest stage: 6-12
hours
2. contractions
strengthen and become
regular
3. each contraction forces
baby’s head against cervix
4. amnion ruptures (water
breaks)
b. stage 2: Expulsion – from full
dilation to delivery
1. as long as 2 hours, normally
around 50 minutes with first
birth and 20 minutes with each
subsequent birth
2. vertex – head first advantages:
skull acts as a wedge, allows
for suctioning of mucus, baby
can breath earlier
breech – buttocks first
3. cesarean section (C-section) –
performed as a result of
prolonged stage 2 labor,
breech, or other problems
c. stage 3: Placental – delivery
of placenta
1. 15 minutes after birth
2. afterbirth – placenta and
attached fetal membranes
3. delivery of placenta
prevents postpartum
bleeding
E. Disorders of Pregnancy
1. Implantation disorders
a. Ectopic pregnancy –
embryo implantation
outside of uterus
b. Placenta previa – growth
of placenta at or near the
cervical opening, often
results in separation of the
placenta from the uterine
wall
c. Abruptio placentae –
separation of a normally
placed placenta from the
uterine wall
2. Preeclampsia (toxemia of
pregnancy) – syndrome that
includes hypertension,
proteinuria (large amounts of
protein in urine – can be due to
hypertension), and edema; may
progress to eclampsia – severe
toxemia that may result in
death
3. Fetal death
a. spontaneous abortion – 1220 weeks (miscarriage
before 12 weeks)
b. stillbirth – after 20 weeks
4. Birth defects/congenital
abnormalities – acquired or
inherited
5. Postpartum disorders
a. Puerperal fever – caused by
bacterial infection and may
progress to septicemia and
death
b. Lactation complications
brought on by anemia,
malnutrition, or other factors
that in turn disrupt infant nutrition
1. Mastitis – inflammation/
infection of the breast
2. Lactose intolerance –
inability to digest milk
c. Depression