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Reproduction & Development
Fertilization: Sperm• 200-500million haploid sperm
cells swim to uterine tube• 30 min-2hrs only 10,000 sperm
reach the uterine tube• Live for up to 48 hours waiting
for oocyte (egg)…only 100 reach the oocyte
• Acrosome cap w/enzymes• Flagellum falls off once enters
egg
Fertilization: Oocyte
• Oocyte 2000x larger than sperm
• Found in upper 1/3 of uterine tube w/in one day if ovulation
• Several sperm required to penetrate corona radiata
• Only one sperm can penetrate the zona pellucida
• Then enzymes prevent other sperm from entering
• This activates oocyte to complete meiosis
Gestation: Prenatal Development
• Cleavage – (day 1-6) – mitotic cell divisions as
travels down uterine tube– w/in 30hrs zygote divides
to form blastomeres– Blastomeres divide every
10-12 hrs– Day 3 – morula – solid
ball of cells– Day 5-6 blastocyst –
hollow ball of cells, cells begin to differentiate
Gestation: Implantation
• Implantation• Day 7-10: blastocyst
adheres to uterine lining• Days 10-12:
differentiation continues to form Amniotic cavity, Yolk sac (blood cell formation), and germ layers
• Germ layers: – Endoderm– Mesoderm– Ectoderm
Gestation: Placentation• Placenta – allows diffusion between fetal and maternal circulation
(blood barrier)• By week 3 – Placenta begins to form
– Produces hCG – prevents mensus
• By week 4 – yolk sac shrinks and fuses into umbilical cord• By week 10-12 – placenta produces estrogens and progesterone,
ovaries become non functional
First TrimesterEmbryonic development
• 3-4 weeks– Neural tube begins
• 5 weeks– 2mm– “c” shaped– Heart bulge– Functional yolk sac & placenta
• 6-7 weeks– .5” (tadpole w/gills slits)– Heart beats– Neural tube closes– Arm & leg buds– Lungs, nostrils, lenses, and dig tract forms
• 8-10 weeks– 1”– Muscles – 1st movements– Ovaries/testes form– Fingers/toes, ears/lips develop– Bones ossify
• 11-13 weeks (Fetus)– 2-3”– Nails, vocal chords, kidneys (urine), and ears– Reflexes, hiccups (diaphragm), rollover, stretch– Pancreas, gall bladder, wbc
Maternal Development• Fatigue• Morning sickness• Tender breasts• Decreased bp, lightheaded & dizzy• Blood volume increases• Require 10-30% more nutrients and
vitamins• Frequent urination
Second TrimesterFetal Development
• 14-18 wks– 4-6” (lobster tail)– Fingerprints, auditory ossicles, teeth, hair &
eyebrows– Make faces, eyes move & detect light– Suck thumb
• 19-22 wks– 8-10” (small grapefruit)– Taste buds, – sense touch, and stress– Perm teeth– Myelination of ns– L/R handed– Ovaries produce eggs
• 23-27 wks– 11-15”, 2lbs (bag coffee)– Recognize voices and respond– Fat deposited– Skin pigmented– Adv. brain functions
Maternal Development
• 90% chance full term• Incr. mucosal secretions• Increase breast size• Pelvis spreads• Pressure on organs• Feel baby move• Indigestion & heartburn• By end: others can feel
baby
Third TrimesterFetal Development
• 28-31 wks– 15-16”, 3.5 lbs– Fully developed (except brain, lungs, liver)– Movements increase
• 32-36 wks– 17-20”, 5lbs– Synapse brain & nerves– Head down position– Adding fat
• 37-40 wks– 21-23”, 6-10lbs– Testes descend into scrotum– Receiving antibodies– When ready: placenta incr. estrogen,
increases oxytocin, stim contractions– Contractions start at top uterus and spread– Moves lower back into pelvis
Maternal Development• Back pain• Swelling• Itchy skin• Hemorrhoids• High bp• Visible kicks/punches• Increase in relaxin
production
Labor & Delivery• Dilation
– avg 15 hrs– Cervix dilates– Contractions 10 – 30 minutes– Amnion ruptures - “water
breaks”• Parturition: expulsion of fetus
– Less than 2 hrs– Cervix pushed open by fetus– Full dilation 10 cm – If canal is too small – Dr
performs episiotomy• Placental After-birth
– Less than 1 hr– Muscle tension in uterus and
shrinking of uterus tears placenta away from uterine wall, placenta is ejected (blood loss)
Premature Labor
• < 14 oz – underdeveloped, no chance of survival
• Between 25-27 weeks – may survive, but with developmental abnormalities
• 28-36 weeks - survival w/normal development
Multiples
• 1/89 Twins– 70% dizygotic – “fraternal” 2 eggs
fertilized at the same time– 30% monozygotic – “identical”
splitting of blastomere– Conjoined twins - incomplete
splitting of blastomere (share skin, liver, other organs)
• 1/7921 triplets