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Fetal Membranes, Placenta and Birth defects

Fetal Membranes, Placenta and Birth defects. Jun Zhou （周俊） School of Medicine, ZheJiang University 20190114. Fetal membrane — overview. Originate from blastocyst, don’t participate in the formation of embryo A collective group which include: 1) Chorion 2) Amnion 3) Yolk sac 4) Allantois

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Fetal Membranes, Placenta and Birth defects

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  1. Fetal Membranes, Placenta andBirth defects Jun Zhou（周俊） School of Medicine, ZheJiang University 20190114

  2. Fetal membrane — overview • Originate from blastocyst, don’t participate in the formation of embryo • A collective group which include: • 1) Chorion • 2) Amnion • 3) Yolk sac • 4) Allantois • 5) Umbilical cord

  3. Chorion • Formed by • trophoblast +extraembryonic mesoderm • Chorion frondosum • (bushy chorion)- embryonic pole • Chorion laeve • (smooth chorion)- abembryonic pole

  4. Development of villi Week 2 to week 3 • Primary villi: cytotrophoblast+syncytiotrophoblast • Secondary villi: extraembryonic mesoderm enter the primary villi • Tertiary villi: extraembryonic mesoderm =>CT+BV

  5. Function of Chorion • Exchange of metabolite: • portion of placenta (Chorion frondosum) • 2) Hormone production: • human chorionic gonadotropin (HCG) • ( Early indication of pregnancy)

  6. Amnion • Amniotic membrane: amniotic epi.+ extraembryonic mesoderm • Amniotic fluid: • Produce:1)amniotic cells • 2) infusion of fluid from maternal blood • 3) urine output from the fetus • 4) pulmonary secretions • Output: 1) absorbed by amniotic cells • 2) fetus swallow • Volume of amniotic fluid: • 800-1000 ml --- 37 weeks • Changes every 3 hours

  7. Amnion - Fluid • Functions • Mechanically cushion • Prevent from fetus adhesion • Help fetal movement • Maintain Temp. • Abnormalities 1) too much (polyhydramnios) >1500 ml Abnormal digestive system or CNS - esophageal atresia - anencephaly 2) too little (oligohydramnios) <500 ml Abnormal urinary system - poor development of kidney - urethra atresia

  8. Yolk sac and Allantois • Yolk sac • Primitive Gut • 3rd week, Germ Cells, (migrate to mesoderm) • 3rd to 6th week, Blood island ( the earliest hemapoietic organ) • Allantois • Caudal extension of hindgut • Allantoic A pairs • Allantoic V pairs Umbilical vessels 2A+1V

  9. Umbilical Cord • Embryonic folding produce a purse string closure • Amnion membrane covered • Cord: mucous CT, 3 vessels,yolk sac ,allantois • At birth, 50-60 cm, 2cm diameter • Too long – knots • Too short – placenta detachment

  10. Placenta - Overview • Functions as: • Lungs, GI tract, Liver, Kidneys, Endocrine • Placenta proper: Chorion frondosum (fetus)+ Decidua basalis (mother)

  11. Anatomy of the Placenta • Fetal – Chorion • Chorion Frondosum • Chorion Laeva • Maternal – Decidua • Decidua Basalis • Decidua Capsularis • Decidua Parietalis

  12. Anatomy of the Placenta • At birth 500 g • 15-25 cm Diameter • 3 cm thick • Anchoring villi • Decidual septa  15-20 Cotyledons

  13. Placental-FetalCirculation • Fetus: umbilical A carries O2/nutrient depleted blood to cap. of chorion , exchange with maternal blood of the intervillous spaceumbilical V • Mother: spiral A intervillous space uterine V

  14. Placental Barrier --the structure between fetal and maternal blood --components: 1)endothelium of chorion capillary 2) CT in the core of the villus 3) trophoblast epithelium

  15. Placental Function 1.Exchange of Metabolites: nutrients antibody, waste 2.Defense barrier 3.hormone production • human chorionic gonadotropin (HCG) Begin: end of 2nd week Highest: 2nd month • Estrogen and progesterone • Placental lactogen

  16. Birth defect, congenital malformation and congenital anomaly • Are synonymous terms used to describe structural, behavioral, functional and metabolic disorders present at birth

  17. Causes of Birth Defects • Genetic/Chromosomal - 15-20% • Environmental (teratogens) - 10-15% • Combined - 20-25% • Multiple Gestations - 1% • Unknown - 40-50%

  18. Genetic Causes • Molecules that regulate development • Enzymes • Structural genes • Localized to a Chromosome – gene unknown

  19. Environmental factors (Teratogens) • Infectious agents-virus • Physical agents X-rays, Hyperthemia, etc • Chemicals agents alcohol, Cocaine, etc • Hormones • Maternal diabetes

  20. Periods of Vulnerability • Preembryonic period Pregerm (0-2 wks) • Usually Death • Embryonic period Organogenesis (3-8 wks) • Abnormalities of Form (malformations) • Fetal period Growth/Maturation (9 wks – birth) • Growth Retardation • Mental dysfunction • Fetus vulnerable • Rapid cell proliferation • Cell migration • Cell differentiation

  21. OBJECTIVES • The components of fetal membrane and their functions. • Structure and function of placenta. • The periods of vulnerability. • Composition of Placenta barrier.

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