ampulla
1. An enlargement at one end of each of the semicircular canals of the inner ear. Each ampulla contains a group of receptors – sensory hair cells – embedded in a gelatinous cap (cupula), which detects movement in one particular dimension, corresponding to the plane of the canal. Movement of the head causes the cupula (and the hairs within it) to bend in a direction opposite to that of the head movement (see illustration); this stimulates nerve impulses in the receptors, which are interpreted by the brain as movement in a particular dimension.

2. Any small vesicle or saclike process.

3. ampulla of Lorenzini See electroreceptor.

ampulla An inflatable sac at the end of each tube-foot in the echinoids (Echinoidea). It controls water pressure in the tube-foot when the muscles in its walls are contracted.

ampulla (am-puul-ă) n. (pl. ampullae) an enlarged or dilated ending of a tube or canal. a. of Vater the dilated part of the common bile duct where it is joined by the pancreatic duct.[ A. Vater (1684–1751), German anatomist]

ampulla vessel for holy oil, etc. OE. — L., dim. of ampora, var. of AMPHORA; for Eng. ampoule, †ampul(le) cf. also (O)F. ampoule.

ampulla a flask for sacred uses such as holding the oil for anointing the sovereign at a coronation. Recorded in this sense from late Middle English, the word is Latin, originally denoting a roughly spherical Roman flask with two handles, and is a diminutive of amphora.