Eye, Ear, and Nose Injuries
Lesson 6: Irrigate an Obstructed Ear
6-2
6-2. STRUCTURE OF THE EAR
a. External Ear. The external ear includes the outer ear (pinna), the auditory canal, and the eardrum. The pinna is the most prominent structure of the external ear. Its shape is maintained by cartilage. The auditory canal is the opening and the canal that runs from the pinna into the skull. This canal ends at the eardrum. The eardrum separates the inner end of the canal from the middle ear. The principal function of the external ear is the collection and conduction of sound waves to the middle and inner ear.
b. Middle Ear. The middle ear (tympanic cavity) is an irregular space in the temporal bone filled with air and containing the three ossicles of the ear: malleus (hammer), incus (anvil), and stapes (stirrup). These bones conduct vibrations from the eardrum to the internal ear. The eustachian tube connects the middle ear with the nasopharynx. Its principal function is to keep the air pressure equal on either side of the eardrum. It is also the avenue of infection by which disease spreads from the throat to the middle ear.
c. Inner Ear. The inner ear contains receptors for hearing and equilibrium. The receptor for hearing lies within the cochlea. The cochlea is coiled and resembles a snail shell. Sound waves, which pass through the external auditory canal, vibrate the eardrum and ossicles, and are transmitted through the fluid of the inner ear. The inner ear also contains three circular canals that control equilibrium.
