[homology-note] "The bilaterian gut is typically a complete tube that opens to the exterior at both ends. It consists of mouth, foregut, midgut, hindgut, and anus (reference 1); 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 (reference 2).[well established][VHOG]" xsd:string {date_retrieved="2012-09-17", external_class="VHOG:0000459", ontology="VHOG", source="ISBN:978-0030259821 Ruppert EE, Fox RS, Barnes RD, Invertebrate zoology: a functional evolutionary approach (2003) p.203, ISBN:978-0521617147 Stevens CE and Hume ID, Comparative physiology of the vertebrate digestive system (2004) p.11", source="http://bgee.unil.ch/"}