Ampullae

Ampulla refers to a dilated sac or chamber in a duct, vessel, or organ. The plural ampullae describes several such dilations. In biology, ampullae often function as storage compartments or as sites of specialized sensory or secretory activity. The term derives from Latin ampulla, meaning flask or bottle.

In sensory anatomy, ampullae are notable in two systems. The ampullae of Lorenzini are electroreceptors in cartilaginous fish, enabling detection of weak electric fields in the water. In the vertebrate inner ear, each semicircular canal ends in an ampulla that contains the crista ampullaris, a sensory organ of balance that detects angular motion through hair cells.

In the digestive system, the hepatopancreatic ampulla (ampulla of Vater) is the dilated junction where the common bile duct and main pancreatic duct merge before emptying into the duodenum. A minor ampulla exists for the accessory pancreatic duct in some species, associated with the minor duodenal papilla.

In invertebrates such as echinoderms, ampullae are part of the hydraulic system that powers tube feet: muscular contraction of the ampulla forces fluid into the podium to extend the foot, aiding locomotion and adhesion.

In vertebrates, the oviduct contains an ampulla, the widened section near the ovary where fertilization commonly occurs in many species; the egg then progresses to the isthmus and uterus in mammals. The term is thus used broadly to describe bottle-shaped or expanded regions across diverse organ systems.