orifice anus BTO:0001680 EV:0100082 TADS:0000066 MA:0000331 anal orifice WBbt:0005364 Orifice at the opposite end of an animal's digestive tract from the mouth. Its function is to expel feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest, such as bones; food material after all the nutrients have been extracted, for example cellulose or lignin; ingested matter which would be toxic if it remained in the digestive tract; and dead or excess gut bacteria and other endosymbionts. UMLS:C0003461 CALOHA:TS-2005 FMA:15711 Wikipedia:Anus NCIT:C43362 FBbt:00047153 GAID:312 SCTID:181262009 TGMA:0001279 opening of terminal part of digestive tract anal opening galen:Anus ectoderm-derived structure