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Because of the large amount of articles, it is hard to display these in specific groups without making the template more confusing.
There is significant cross-over in these topics, there are also many structures and articles unique to each topic. A split would retain common structures in each template but also allow unique topics to be added, including a suite about sex determination, sexual differentiation, and sexual dimorphism, which are very relevant topics.
There is no reason that we need to be beholden to the terminology in Gray's Anatomy