An organ that aids digestion and stores bile produced by the liver[WP].
Comment:
Rats do not have a gallbladder, but produce bile. The bile flows directly from the liver through the (hepatic) bile duct into the small intestine (Hebel and Stromberg, 1988); [homology-note] "The presence of a gallbladder appears to be a primitive trait. It is found in most fish and all adult reptiles and amphibians and has been well conserved in mammals, for the most part.[well established][VHOG]" xsd:string {date_retrieved="2012-09-17", external_class="VHOG:0000221", ontology="VHOG", source="DOI:10.1002/(SICI)1097-0029(19970915)38:6<571::AID-JEMT3>3.0.CO;2-I Oldham-Ott CK, Gilloteaux J, Comparative morphology of the gallbladder and biliary tract in vertebrates: Variation in structure, homology in function and gallstones. Microscopy research and technique (1997)", source="http://bgee.unil.ch/"}