@marzi1 Thank you for the suggestion. We do ask, and require, that an MCAT-specific source citation be included with any and all content-related suggestions, in order to streamline the process of suggestions and deck maintenance. More information can be found here: AnKing MCAT Deck Submission Guidelines
Please let me know if you have any other questions. 
The placenta is fetal-maternal tissue. Starts as maternal and they build together. Regardless, this is outside the scope of the mcat.