10.2 Development of the placental villi

• Anatomy of the placenta
• The three villus types
  • The cytotrophoblast layer
• Connections between maternal and fetal tissues
  • Placental tissue structure
  • Development of the placenta
  • The decidua
  • Development of the villi
    

Anatomy of the placenta

In order to understand the chronological development of the chorionic villi it is important to have a comprehensive overview of placental anatomy. In this diagram, the placenta is roughly four months old and various fundamental structures can be recognized, namely the umbilical cord, the amnion, the chorionic plate, the already advanced branching of the villi, the basal plate and the cotyledon.

Fig. 13
Schematic diagram of the placenta at around the fourth month in a sagittal section.

Note: Zone A corresponds to the interactive diagram of this module

At birth, the placenta consists of two parts:

• maternal portion
• fetal portion

Fig. 14
Placenta: View from the maternal side
Fig. 15
Placenta: view from the fetal side

Fig. 16
From the maternal side the placenta has a wrinkled surface, characterized by the cotyledons.
Fig. 17
From the fetal side, the placenta is smooth and shiny. Notice the normal, central insertion of the umbilical cord in this case.

© Institut de pathologie, CHUV, Lausanne