The anus and surrounding regions. Encompasses both internal and external regions, where present.
Comment:
[homology-note] "Although all vertebrates have a digestive tract and accessory glands, various parts of this system are not necessarily homologous, analogous, or even present in all species. Therefore, broad comparisons can be best made under the listings of headgut, foregut, midgut, pancreas and biliary system, hindgut.[uncertain][VHOG]" xsd:string {date_retrieved="2012-09-17", external_class="VHOG:0000395", ontology="VHOG", source="ISBN:978-0521617147 Stevens CE and Hume ID, Comparative physiology of the vertebrate digestive system (2004) p.11", source="http://bgee.unil.ch/"}