Ugh, I feel like I might regret answering this, but....
...According to Hespith in DAO, they repeatedly force you to eat parts of them and other people they have captured until she was bloated with their own corruption. Hespith did mentioned in her poem that the turned woman was violated at one point, along with other violent behaviours, but did not expand on what that meant (it doesn't necessarily require darkspawn to be anatomically correct, as you put it). And if they are still anatomically correct - giving how much flesh they're missing, or is shrivelled away - I doubt they're entirely functional.
Hespith draws more correlation between the devouring of the others' flesh and the turned woman growing and distorting, and that is the main reason contributor. Specifically, in a now deleted thread, David Gaider said that broodmothers were ghouls whose corruption was artificially accelerated, which would be what all that devouring of other ghouls was for.