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Fetal Membranes & Placenta

Fetal Membranes & Placenta. Protection Nutrition Respiration Excretion Hormone. Chorion Amnion Yolk sac Allantois. Changes in the Trophoblast. By the beginning of the 2 nd month, trophoblast is characterized by a great number of 2° & 3° villi that give it a radial appearance.

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Fetal Membranes & Placenta

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  1. Fetal Membranes & Placenta Protection Nutrition Respiration Excretion Hormone Chorion Amnion Yolk sac Allantois

  2. Changes in the Trophoblast • By the beginning of the 2nd month, trophoblast is characterized by a great number of 2° & 3° villi that give it a radial appearance. • Chorionic plate • Outer cytotrophoblast shell • Lacunar or intervillous spaces • Syncytial knots –

  3. Chorion Frondosum &Decidua Basalis • Chorion frondosum (bushy or villous chorion) • Chorion laeve (smooth chorion) • Decidua basalis • Decidua capsularis • Decidua parietalis (decidua vera) • Placenta – • Amniochorionic membrane

  4. Structure of the Placenta • By the beginning of the 4th month, placenta has 2 components: • Fetal portion – • Maternal portion – • Chorionic & decidual plates • Junctional zone • Decidual septa & cotyledons

  5. Full-term Placenta • At full term, placenta is discoid with a diameter of 15~25 cm, is approximately 3 cm thick, & weighs about 500~600 g. • Maternal side – • Fetal surface –

  6. Circulation of the Placenta • The intervillous spaces of a mature placenta contain approximately 150 ml of blood, which is replenished about 3 or 4 times per minute. • Placental membrane / barrier (x) – – • Hemochorial type

  7. Function of the Placenta • Exchange of metabolic & gaseous products between maternal & fetal bloodstreams • Exchange of gases – • Exchange of nutrients & electrolytes – • Transmission of maternal antibodies – • Production of hormones –

  8. Amnion & Umbilical Cord • Primitive umbilical ring – • Primitive umbilical cord – • Physiological umbilical hernia • Jelly of Wharton

  9. Amniotic Fluid • The amniotic cavity is filled with a clear, watery fluid that is produced by amniotic cells but is derived primarily from maternal blood. • Amount – • Circulation – • Function–

  10. Fetal Membranes in Twins • Arrangement of fetal membranes in twins varies considerably, depending on the type of twins & on the time of separation of monozygotic twins.

  11. Dizygotic Twins

  12. Monozygotic Twins

  13. Frequency of Types of Placentas & Fetal Membranes in Monozygotic (MZ) & Dizygotic (DZ) Twins

  14. Conjoind (Siamese) twins

  15. Parturition (Birth) • Stage 1 : effacement & dilatation of cervix • Stage 2 : delivery of fetus • Stage 3 : delivery of placenta & fetal membranes

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