In anatomy, an ampulla is a dilated, bulb-like portion of a tubular structure. In other words, they are types of ducts or canals found in the human body. The ear, for example, has ampullae — the plural of ampulla — in it. Ampullae are important parts of the body that tend to serve as a holding place for something moving through the body, as a juncture where chemical reactions or other activities can occur, or as a sensory organ.
Ampullae exist in animals and humans. In humans, the enlarged ends of each of three semicircular bony canals in the inner ear are known as osseous ampullae. Tiny hairs in in these ampullae help to keep the brain informed of how the head is oriented, helping the person's sense of balance. The rectal ampulla, on the other hand, is the dilated portion of the rectum just above the anal canal. The human body stores fecal material in the rectal ampulla before expelling it.
The ampulla of Vater, another type of ampulla, is named for German anatomist Abraham Vater who first discussed the body part in the 1700s. Also known as the hepatopancreatic ampulla, it is the enlarged point where the ducts from the liver and pancreas come together and lead into the duodendum — the first part of the small intestine. The ampulla of Vater transport bile out of the body, but first that bile mixes with food in the small intestine to help digestion.
The ampulla of vas deferens in males is the enlarged end of the vas deferens. This ampulla lies behind the urinary bladder and is a tube that carries sperm from where they are stored in the epididymis toward a gland called the seminal vesicle to form an ejaculatory duct.
The ampulla of the uterine tube is the middle part of the uterine tube in female humans. It is here that a woman's egg typically meets sperm if fertilization is to occur. The ampulla contains muscle and hair-like structures called cilia to help move a fertilized egg toward the uterus. An unfertilized egg, however, will degenerate in the ampulla.
Ampullae also exist in other animals. The ampullae of Lorenzini, for example, are part of a network of gel-filled canals visible just beneath the skin of sharks and some other fish. These ampullae perform a sensory function, a bit like the osseous ampullae in humans. The ampullae of Lorenzini, however, are electroreceptors. They enable fish to detect electromagnetic fields in the water. This is thought to play a role in the ability of fish to detect prey, as well as changes in water temperature.