"Chorion" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings). Descriptors are arranged in a hierarchical structure, which enables searching at various levels of specificity.
MeSH information
The outermost extra-embryonic membrane surrounding the developing embryo. In REPTILES and BIRDS, it adheres to the shell and allows exchange of gases between the egg and its environment. In MAMMALS, the chorion evolves into the fetal contribution of the PLACENTA.

This graph shows the total number of publications written about "Chorion" by people in this website by year, and whether "Chorion" was a major or minor topic of these publications.
Bar chart showing 271 publications over 25 distinct years, with a maximum of 22 publications in 2013 and 2015
To see the data from this visualization as text, click here.