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

2. Fetal membrane — overview
Originate from blastocyst, don’t participate in the formation of embryo
Including:
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

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

7. 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
30 ml weeks
450 ml weeks
ml weeks---circulate

8. Amnion - Fluid Functions Abnormalities Mechanically cushion
Protect from fetus adhesion
Movement
Maintain Temp
Abnormalities
1) too much (polyhydramnios)
>2000 ml
Abnormal digestive system or CNS
- esophageal atresia
- anencephaly
2) too little (oligohydramnios)
<500 ml
Abnormal urinary system
- poor development of kidney
- urethra atresia

9. Yolk sac and Allantois Yolk sac Allantois Primitive Gut
3rd week, Germ Cells
3rd to 6th week,
Blood island
Allantois
Caudal extension of hindgut
Allantoic A pairs
Allantoic V pairs
Umbilical vessels 2A+1V

10. Umbilical Cord Folding – a purse string closure
Amnion membrane covered
Cord: mucous CT, 3 vessels,yolk sac ,allantois
At birth, cm, 2cm diameter
Long – knots
Short – placenta detachment

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

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

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

15. Placental-Fetal Circulation
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

16. --the structure between fetal and maternal blood --components:
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

17. 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

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

19. Causes of Birth Defects
Genetic/Chromosomal %
Environmental (teratogens) %
Combined %
Multiple Gestations - 1%
Unknown %

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

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

22. 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

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