For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Christ described the marriage as joining of a man and a woman.into one body. Thus, they become one. And their union? "Let no man put asunder meaning no man can breakup their union except God (or their church)." So, there is no LONGER BEING master nor slave IN THEIR RELATIONSHIP because they are no longer two but one. What does this mean? They are equal!
I think whenever this is discussed what often gets lost is the reciprocal to wives not having authority over their body nor does does the husband over his body...
1 Corinthians 7:4
..... Likewise the husband does not have authority over his own body, but the wife does.