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Pregnancy and Fetal Development Fetal Development

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Pregnancy and Fetal Development Fetal Development Powered By Docstoc
					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
                  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
                           First Trimester
                                                                   Maternal Development
              Embryonic development
                                                          •   Fatigue
•   3-4 weeks
     – Neural tube begins                                 •   Morning sickness
•   5 weeks                                               •   Tender breasts
     – 2mm                                                •   Decreased bp, lightheaded & dizzy
     – “c” shaped                                         •   Blood volume increases
     – Heart bulge                                        •   Require 10-30% more nutrients and
     – Functional yolk sac & placenta                         vitamins
•   6-7 weeks                                             •   Frequent urination
     – .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
                          Second Trimester
                   Fetal Development                             Maternal Development
•   14-18 wks
     –   4-6” (lobster tail)
                                                          •   90% chance full term
     –   Fingerprints, auditory ossicles, teeth, hair &   •   Incr. mucosal secretions
         eyebrows
     –   Make faces, eyes move & detect light             •   Increase breast size
     –   Suck thumb                                       •   Pelvis spreads
•   19-22 wks                                             •   Pressure on organs
     –   8-10” (small grapefruit)
     –   Taste buds,                                      •   Feel baby move
     –   sense touch, and stress                          •   Indigestion & heartburn
     –   Perm teeth
     –   Myelination of ns                                •   By end: others can feel
     –   L/R handed                                           baby
     –   Ovaries produce eggs
•   23-27 wks
     –   11-15”, 2lbs (bag coffee)
     –   Recognize voices and respond
     –   Fat deposited
     –   Skin pigmented
     –   Adv. brain functions
                          Third Trimester
             Fetal Development                           Maternal Development
•   28-31 wks                                        •   Back pain
    – 15-16”, 3.5 lbs                                •   Swelling
    – Fully developed (except brain, lungs, liver)   •   Itchy skin
    – Movements increase                             •   Hemorrhoids
•   32-36 wks                                        •   High bp
    –   17-20”, 5lbs
                                                     •   Visible kicks/punches
    –   Synapse brain & nerves
    –   Head down position                           •   Increase in relaxin
                                                         production
    –   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

				
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