Download Chapter 27 Reproductive Endocrinology

Chapter 28 Pregnancy and Development
Pregnancy and Development
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Embryology
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1 cell
organism
process :
• fertilization
• mitosis
• cell specialization
• cell destination
gestation
fusion of gametes (nuclei)
1 cell  trillions
structure and function
get to the right place
= pregnancy
• 280 days
from last menstrual cycle
getting together
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2 gametes  1 zygote
sperm : vagina  cervix  uterus  fallopian tube
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it’s not easy :
– acidic vagina
– cervix open by estrogen ~ 24 hours
– uterus : contractions ; phagocytes
– fallopian tube – cilia
– ~ 200 sperm make it
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ovum : ovary  fimbriae  fallopian tube
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oocyte protected by
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acrosomal reaction
• fimbriae beat inward
• cilia propel ovum toward uterus
fertilization
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outer corona radiata
inner zona pellucida
enzymes dissolve zona pellucida
requires many acrosomes (sperm)
cortical reaction
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blocks to polyspermy:
• Na diffuses in - depolarization
• zonal inhibiting enzymes
(fast block)
(slow block)
Ca released – initiates meiosis II
complete meiosis II
fusion of nuclei
23 + 23 = 46
(diploid)
stages
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zygote
1 cell
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pre-embryo
1st 2 weeks
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embryo
week 3 – 8
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fetus
week 9 - birth
st
(week 1 – 8)
pre-embryonic growth
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cleavage
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mitotic divisions
morula
16 + cells in a ball
100 cells
~ day 3
~ day 4-5
enter uterus ~ day 4
blastocyst
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hollows in center
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blastoceole
trophoblast
future chorion
inner cell mass
future embryonic disc
twins
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identical
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monozygotic twins
zygote splits in two (or inner cell mass)
adjacent on uterus
adjacent or same placenta
fraternal
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dizygotic twins
2 ovum
+ 2 different sperm
2 different placenta
implantation
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day 6 – 7
; complete by day 14
trophoblast fuses with endometrium
trophoblast secretes :
hCG
maintains corpus luteum
digestive enzymes
digests endometrium cells
growth factors
endometrium growth (inflamm)
ideal location - posterior superior uterus
ectopic pregnancy
• implantation not in uterus
placenta
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Placenta = chorion + endometrium
chorion
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part of trophoblast
chorionic villi
• fetal blood vessels
• produce anti-coagulant
endometrium
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maternal blood vessels
lacunae
blood filled spaces
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functional by end of 3 month
produces estrogen , progesterone
embryonic nutrition
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initial
cytoplasm of ovum
implantation enzymes dissolve uterine cells
endometrium
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supply for 8 – 12 weeks
fetal circulation forms week 3 - 4
placenta
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blood flow starts day 16
fully functional week 10 - 12
cross-placenta transport
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nutrients
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diffusion
glucose
lipids
Na , K , Cl
nutrients
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active transport
AA
Ca
oxygen
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diffusion
fetal hemoglobin – greater affinity for O2 than adult Hb
carbon dioxide
diffusion
wastes
diffusion
embryonic membranes
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from original zygote, but not part of embryo
chorion
fetal part of placenta
amnion
fluid filled sac
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amniotic fluid
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surrounds fetus
protection
collects urine
future “gut”
produces early blood cells
yolk sac
tests
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hCG
pregnancy test
Chorionic Villi sampling
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CVS
biopsy of chorionic villi
embryonic cells - not part of embryo
~ 8+ weeks
amniocentesis
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amniotic fluid
fetal cells
16 – 18 weeks
ultrasound
gastrulation
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= formation of 3 primary germ layers
primitive streak
3 primary germ layers
ectoderm
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nervous system , epidermis
mesoderm
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middle
connective tissues, solid organs
endoderm
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outer
linings of tracts, cavities
inner
end of embryonic stage
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~ 1 inch
all organs and tissues formed
most are functioning
heart beats since week 3 ½
brain waves recorded since week 7
vascular system complete
limbs and digits present
able to read, change TV channels, use CD player, iPod
How does this happen ?
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toolkit genes
control development
> 5% of genome
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cell differentiation
turn on / off genes
make different proteins
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transcription factors
cytoplasmic determinants
master genes
turn on tissue specific genes
cell environment
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cell location (cell map)
concentration of extracellular chemicals
induction
adjacent cells
Stem Cells
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totipotent
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pluripotent
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inner cell mass
multipotent
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cell able to create entire organism
zygote, early cleavage cells
can create all cells except trophoblast
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embryonic stem cells
can become a few different cells
neural stem cells
hematopoietic stem cells
unipotent
basal cells
reproductive cloning
create entire adult organism
therapeutic cloning
create specific tissues
cancer as a stem cell problem
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mitosis problem
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unresponsive to braking signals (growth limiters)
telomeres
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anaplasia
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histogenic assumption
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failure to differentiate
multipotent don’t differentiate to adult cells
adult cells lose differentiation
become cancerous cells
probably doesn’t occur
angiogenesis
stim vascular growth ( as in normal development)
fetal development
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weeks 9 – 38
cell specialization
detailed tissue
organ development
growth
metabolic changes - mother
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hPL human placental lactogen
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mammary development
glucose-sparing
gestational diabetes
effect of mother’s glucose levels on fetus’ insulin
hCT human chorionic thyrotropin
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like TSH
relaxin
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relaxes pubic symphysis, pelvic ligaments and muscles
physiologic changes - mother
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morning sickness
hi estrogen, progesterone
polyuria
urinating for 2
stress incontinence
pressure on urinary bladder
hyperglycemia
cortisol effect
cardiovascular
increase blood volume > 25%
increase BP
increase CO
increased BMR
~ hCT
varicose veins
decrease venous return from LE
respiration
increased rate
~ hPL
hormones
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hCG =
human chorionic gonadotropin
estrogen + progesterone
inhibit ovulation
estrogen
placenta, mammary ducts
progesterone
placenta, mammary glands
inhibit myometrium
oxytocin
uterus contractions
parturition = birth
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 estrogen
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oxytocin receptors
 progesterone
Braxton-Hicks contractions false labor
oxytocin
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allows myometrium activity
(and prostaglandins)
rhythmic contractions
positive feedback
pain
more oxytocin
stretch of cervix
hypoxia of uterus (vasospasm)
stages of labor
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stage 1
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dilation
1 cm - 10 cm
hours to day +
cervix effaces (thins)
amnion bursts
stage 2
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expulsion
~ 50 min
crowning baby’s head at vulva
stage 3
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placental
(afterbirth)
uterine contractions detach blood vessels / placenta
15 – 20 min after baby
infant
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st
neonatal
1 4 weeks
umbilical cord cut
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 CO2
- central acidosis
CNS stim respiration
inhalation -
 pulmonary circulation  L atrium pressure
closes foramen ovale and ductus arteriosus
Apgar score 0 – 10
healthy = 8 - 10