Fetal membranes

DEFINITION

ANY STRUCTURE THAT FUNCTIONS FOR THE PROTECTION, NOURISHMENT, RESPIRATION OR EXCRETION OF A DEVELOPING FETUS. THEY INCLUDE:


• Chorion
• Amnion
• Placenta
• Allantois
• Yolk sac
• Umbilical cord


Chorion Frondosum

In early weeks of development villi cover the entire surface of
chorion as it advances villi on embriyonic pole continue to grow
and expand give rise to the chorion frondosum

DECIDUA
A mucous membrane lining the uterus,modified during pregnancy
and shed at parturation or during menstruation
• Chorion frondosum (bushy or villous chorion)
• Chorion laeve (smooth chorion)
• Decidua basalis
• Decidua capsularis
• Decidua parietalis (decidua vera)

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

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)

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

Fetal membranes in twins
Comparison of monozygotic and dizygotic twins

Monozygotic twins

Two babies developing
From similar zygote.
.Babies have one amnion , placenta and separate chorion.
.Babies have similar sex,
Habbits and blood group.


Dizygotic twins

Two ova fertilized by two Sperms.
.Each baby having its
Own amnion ,chorion and placenta.
.Babies may be males or female or may be one of
them is male and other
Is female.