Teiary stem villi consists of:-
Secondary villi:- contains a central core of primary (extra embryonic) mesoderm and is covered by cyto- and syncytio- trophoblast cells. Teiary villicontains fetal blood vessels invading the extra embryonic mesoderm and is covered by trophoblastic cells.
Embryology and Histology
Central core of cytotrophoblast covered with synctiotrophoblast
Central core of extra-embryonic mesoderm covered by central cyto- and peripheral synctio- trophoblast
Central maternal blood vessels surrounded by mesoderm and trophoblast
Central fetal blood vessels surrounded by mesoderm and trophoblast
Central fetal blood vessels surrounded by mesoderm and trophoblast