What is the primary function of the chorion during embryonic development?

The chorion plays a crucial role during embryonic development, primarily facilitating gas exchange between the developing embryo and its environment. It forms the outer membrane surrounding the embryo and, in many species, is involved in the exchange of respiratory gases, allowing oxygen to enter and carbon dioxide to exit. This is particularly important as the embryo develops, as it requires a continual supply of oxygen for cellular respiration and growth.

In addition to gas exchange, the chorion may also participate in the formation of the placenta in species where this structure is present, further enhancing the efficiency of gas and nutrient exchange. Thus, its primary function during embryonic development relates to ensuring that the embryo can breathe and obtain the necessary oxygen to support growth and development.