Yevamos 91a — Zonah: Loss of Kehunah or a New Pesul?

When a Bas Kohen becomes a zonah, why does she lose her right to eat terumah? Does the status of zonah actually strip away her Kedushas Kehunah, or does she remain a Bas Kohen while acquiring a new pesul that prevents her from eating terumah? A fascinating chakirah that may lie at the heart of a dispute between the Rambam and Tosafos—and has surprising implications for a Bas Levi and Maaser Rishon.