Fertilization

Fertilization

1. risk of birth defect

   • greatest
     • during embryonic period at five weeks gestation
       • hydatidiform moles
         • formed from trophoblast
           • may become invasive
             • choriocarcinomas
     • 3-8 weeks
       • first prenatal visit usually at 8 weeks
         • 2nd slide-test ?
           • start prenatal care before pregnancy

2. not efficient

   • 50% embryos lost
     • 50% with chromosomal abnormalities

3. morula (3 days)

   • compacted embryo
     • Blastocyst (4-5 days)
       • Implanting blastocyst (6 days)
         • outer cell mass-trophoblast
           • expresses selectins
             • carbohydrate binding proteins
             • uterine epithelium
               • expresses carbohydrate receptors for selectins
         • syncytiotrophoblast
           • erodes uterine wall
         • embryo is foreign body
           • mother immune system
             • shifts from cell to antibody mediated immunity
               • risk of infection increases
               • cell mediated autoimmune disease improves
               • antibody mediated autoimmune disease worsens
         • ectopic pregnancies
           • uterine tube (95%)
           • Rectouterine pouch (Douglas' pouch
         • implanted embryo (7.5 days)
           • 9-13 days: look at slide 16
             • 2nd week: week of twos
               • trophoblast
                 • syncytiotrophoblast
                 • cytotrophoblast
                   • make more cells
               • extraembryonic mesoderm
                 • visceral (splanchnic)
                 • parietal (somatic)
               • embryonic disc (7.5 days)
                 • epiblast
                 • hypoblast
             • gene expression (15 days)
               • in anterior visceral endoderm
                 • establishes head region
               • gastrulation (16 days)
                 • epiblast cells move towards primitive streak
                   • creates two new layers
                     • formation of prechordal plate and notochord
                 • three germ layers
                   • ectoderm
                     • skin, CNS, PNS, eyes, internal ear, neural crest cells
                   • mesoderm
                     • bones, connective tissue, urogenital system, cardiovascular system
                   • endoderm
                     • gut and gut derivatives
                   • all three germ layers originate from epiblast
                     • hypoblast will migrate down to yolk sac or die
     • tight junctions
     • outside-placenta inside -embryo
   • like a berry

4. ART

   • Assisted Reproductive Technologies
     • fertility treatments
       • eggs and sperm handled in lab
         • placed in cultured medium
           • fertilized eggs placed in uterus
             • adverse outcomes
               • spontaneous abortion
               • multiple births
               • birth defects
                 • heart, urogenital, gasrointestinal, muscle, cerbral palsy
                 • 28% higher
               • low birth weight