Medieval Religious Institutions

When looking different things up for research paper ideas I came across many different medieval institutions (mainly religious) that are still around today. These institutions came about during the crusading era and in some cases played very large roles in certain conflicts. Two I found that had full fledged websites, membership info, etc. were the Dominicans and The Franciscans. Their respective websites are http://www.op.org/ and http://www.franciscans.org/. I find it very interesting that an institution can have trouble lasting a few years in modern society, but these have lasted for many hundreds of years. It raises the question with me as to why religious ideals can last, when ethical and moral based groups cannot. Those types of groups may change drastically over the years to maintain stability, but the Bible, Koran, etc. are the same book they always have been.