Dr Henry Knipe and Radswiki et al.

The chorion is one of the embryonic membranous structures than encloses both the fetus as well as the amnion. The chorion begins to form chorionic villi towards its outer surface, which initially serves to provide nutrition to the developing embryo. 

Part of the chorionic villi arborize more extensively and forms the chorionic frondosum, which in turn gives rise to the placenta. 

History and etymology

The word chorion derives from the Greek word χόριο meaning skin. Galen was the first to apply the term to the fetus.

Related pathology

Anatomy: Abdominopelvic
Ultrasound - obstetric
Share article

Article information

rID: 15177
System: Obstetrics
Section: Anatomy
Synonyms or Alternate Spellings:
  • Chorionic sac

Support Radiopaedia and see fewer ads

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.