英语中由破折号引出的句子在句子成分中扮演什么角色,懂英语的进,不懂得热心人勿入,谢谢.

英语中由破折号引出的句子在句子成分中扮演什么角色,懂英语的进,不懂得热心人勿入,谢谢.
这是有关英王亨利八世的bibliograpy里面的一个句子.请帮我分析一下破折号引出的句子在句子中做什么成分?可以不可以不要破折号,也就是把破折号改成逗号?
On the 16th,hoping probably to save herself by these means,she informed Cranmer of a certain supposed impediment to her marriage with the king-according to some accounts a previous marriage with Northumberland,though the latter solemnly and positively denied it-which was never disclosed,but which,having been considered by the
archbishop and a committee of ecclesiastical lawyers,was pronounced,on the 17th,sufficient to invadidate her marriage.请问
-according to some accounts a previous marriage with Northumberland,though the latter solemnly and positively denied it-可以把破折号改成逗号吗?为什么?