ampulla of vas deferens ampulla of vas deferens the ampulla of vas deferens, also called the ampulla of ductus deferens, is an enlargement of the vas deferens at the fundus of the bladder which acts as a reservoir for sperm. this structure is seen in some mammalian and squamate species and is sometimes tortuous in shape. ampulla of vas deferens ampulla of ductus deferensprostate with seminal vesicles and ducts, viewed from in front and above.seminal vesicles and ampulla of vas deferens, seen from the front.detailsidentifierslatinampulla vas deferentis ampulla ductus deferentisanatomical terminology