There are three bones located in the middle ear: the incus, the malleus and the stapes. Collectively, all three bones comprise the ossicles.
Sound waves provoke vibration in these bones, after traveling from the external ear, through the ear canal and beyond the tympanic membrane (eardrum). These vibrations then travel into the cochlea, where sound is translated into nervous system signals that are sent to the brain.
The incus lays at the center of the ossicles, connecting the malleus to the stapes. It is shaped like an anvil, which is why "the anvil" is a widely used alternative name for the bone.
The bone has a few basic regions. One of its surfaces, called the head, forms a joint with the malleus ossicle. The incus also has two extensions known as the long and short crus. At the end of the long crus is the lenticular process, a hooked-shaped part of the incus that forms a joint with the head of the stapes. The short crus attaches to the back wall of the middle ear cavity, which houses the ossicles. The center of the incus is also known as the body.