A portcullis was used as a big metal door at the front of a castle, there was sometimes two of them so if the enemy got past the first one he would be stuck in the middle and they would pour e.g boiling oil on him
Medieval dental care was usually provided by surgeons. A surgeon was not the same as a physician, who was more highly educated. Surgeons also tended wounded soldiers or people with broken bones....
When moats were in style, during times when your neighbors were far off and liable to want your land, some castles used a moat as a natural defence, when no other form of natural terrain advantage...