Stapes
From Memory Alpha, the free Star Trek reference
The stapes is a stirrup-shaped small bone in the middle ear. It is the smallest and lightest bone in a Human body.
In 2371, while on board the USS Voyager, Kes was studying medical texts to become a nurse. While in sickbay, The Doctor tested Kes on the bones of the ear, including stapes. (VOY: "Eye of the Needle")
