mucus

1. N-UNCOUNT Mucus is a thick liquid that is produced in some parts of your body, for example the inside of your nose. (身躰分泌的) 黏液

...the thin layer of mucus that helps protect the delicate lining of the rectum. 有助於保護嬌嫩的直腸內壁的那層薄薄的黏液。