In bony fish and tetrapods the external opening into the inner ear has been lost.

It is the external opening to an extremely sensitive infrared detecting organ.

It is deep in the Earth and has no external openings.

The minimum external openings make the gallery easily adaptable, to accommodate the wide range of media on show.

Creation of an artificial external opening into the stomach for nutritional support or gastrointestinal compression.

With extreme damage to the septum, the two nostrils are no longer separated and form a single larger external opening.

The first thing he did when he left the conning-tower was to hermetically close every external opening in the ship.

The external opening of the ear still lies at the base of the jaw.

It is the only mammalian species to lack an external vaginal opening.