accessory organ
Anatomical term for an organ that assists the function of another related organ, such as glands or ducts.
肝臓の副器官として胆嚢が挙げられる。
The gallbladder is cited as an accessory organ of the liver.
Compound of 副 (ふく, 'accessory, auxiliary') and 器官 (きかん, 'organ').