Otitis media ear infection. Montage of three illustrations forming a sequence showing the middle ear affected by otitis media, and the progression from a healthy state (left) to a severe infection and a perforated eardrum (right). Otitis media is inflammation of the middle ear due to an infection in the eustachian tube (lower right) which joins the middle ear to the nasal cavity. The infection causes blockage of the tube, and a build-up of pus (yellow) occurs behind the eardrum (red). This causes ear pain and impaired hearing. The infection can usually be cleared up with antibiotics. Also seen is the cochlea (purple) which detects sound, and the stapes, incus and malleus ear bones (light brown). Semicircular canals (purple) control balance.