ANY STRUCTURE THAT FUNCTIONS FOR THE PROTECTION, NOURISHMENT, RESPIRATION OR EXCRETION OF A DEVELOPING FETUS. THEY INCLUDE:
• Yolk sac
• Umbilical cord
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
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:
Chorionic & decidual plates
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
Two babies developing
From similar zygote.
.Babies have one amnion , placenta and separate chorion.
.Babies have similar sex,
Habbits and blood group.
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