Chorion

Full Definition

The chorion is the outermost extraembryonic membrane that surrounds the embryo and other membranes during pregnancy. It develops from the trophoblast and contributes to placental formation through the development of chorionic villi. The chorion is distinct from the amnion (inner membrane) and plays a crucial role in maternal-fetal exchange. Understanding this distinction is important when editing documents about prenatal diagnosis, as chorionic villus sampling specifically targets this membrane.

Usage

Usage note: Often confused with amnion; chorion is the outer membrane.

In Context

• "The chorion develops into the fetal portion of the placenta." — Embryology textbook
• "Chorionic membrane rupture was identified during examination." — Clinical documentation