The malleus articulates to incus which connects to the stapes. The ossicles are the malleus (hammer), incus (anvil), and the stapes (stirrup). The stapes is one of three ossicles in mammals. The ossicles (malleus, incus and stapes) normally appear during the first half of fetal development. The middle ear contains three tiny bones known as the ossicles&colon; "malleus", "incus", and "stapes". Conductive hearing loss is usually concomitant with impingement of abnormal bone on the stapes footplate. Vibrations of the stapes footplate introduce pressure waves in the inner ear. The "vestibular duct" ends at the oval window, where the footplate of the stapes sits. These structures usually include the stapes (a stirrup-shaped auditory ossicle). The ability of the tympanum and stapes to effectively transmit vibrations is called impedance matching. The stapes bone transmits movement to the oval window. The second is a congenital malformation of the stapes. A rare element present is the furcula and the stapes of the ear. The long crus articulates with the stapes at the lenticular process. Fixation of the stapes within the oval window causes a conductive hearing loss.