What does the placenta consist of?
You could’ve easily googled this, but anyway...

Placenta is a composite structure made of embryonic and maternal tissues. 
The placenta is composed of: The chorion, which is the embryonic-derived portion of the placenta. Chorion contains the trophoblast cells (cells that make up the outer cell layer of the blastocyst). finger-like structures called chorionic villi are also present in the placenta. Lastly, the space in the placenta that surrounds the villi and the maternal blood is called the intervillous space.

Source: https://study.com/academy/lesson/the-placenta-and-the-fetus-structure-and-function.html