肛管直肠环是由哪些结构组成（ ）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='25456' and id < 2144644 and id<>'2144644' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='25456' and id > 2144644 and id<>'2144644' order by id asc limit 5