yep! just let mom know this seems to be the childs topic of choice lately, ask her to handle it at home. Let her know your plan of action while the child is with you..i.e.: you will inform the child there is a time and place to talk about these things and perhaps also to only talk about these things with mommy or Daddy. use the phrase. "this is not daycare talk, this is home talk"
not a big deal for kids to question body functions and such, but its really not our job to educate that personal of topic, for Mom's and Dad's to address.