noun
Standard anatomical term; used in medical and everyday contexts.
肛門は消化管の末端にある開口部です。
The anus is the opening at the end of the digestive tract.
The kanji 肛 means 'anus' and 門 means 'gate'; together they form the anatomical term for the anal opening. The reading こうもん is the on'yomi of both characters.