chorion vs mesentery

chorion

noun
  • The protective and nutritive membrane in higher vertebrates that attaches the fetus to the uterus. 

  • The outer membrane of seeds of plants. 

  • The outer case of an insect egg. 

mesentery

noun
  • The membrane that attaches the intestines to the wall of the abdomen, maintaining their position in the abdominal cavity, and supplying them with blood vessels, nerves, and lymphatics. 

How often have the words chorion and mesentery occurred in a corpus of books? (source: Google Ngram Viewer )