Personal Health Ears

Function A. Function of ears is to gather sensory information: 1. Sound waves for sense of hearing 2. Gravity and movement for sense of balance.

Structure 1. The outer ear is also know as the auricle. A. The external auditory canal goes through the bone of the skull. B. The canal is protected by tiny hairs and glands that secrete wax. C. The tympanic membrane (or the eardrum) is at the inner end of the canal.

2. The middle ear has: A. Small bones called ossicles named for their shape: Malleus(hammer), incus(anvil), and stapes(stirrup) which is the smallest bone. B. The middle ear is drained by a oval window.

3. The inner ear, or labyrinth, has three important parts: A. The outermost, or cochlea, that turns sound vibrations into nerve impulses. The path of sound waves in hearing is: 1. Enter the external auditory canal. 2. Eardrum vibrates. 3. Vibrations are carried across the middle ear by the ossicles.

4. Travel through the inner ear. 5. Converted into nerve impulses. 6. Sent to the brain. The cochlear branch of the auditory nerve carries impulses to the brain for interpretation as sound. In binaural hearing, brain notices differences in loudness in each ear and can determine direction from which sound came.

B. The central, vestibule, and innermost, semicircular canals are responsible for balance: Each canal has an organ called a crista with hair cells in a fluid. Gravity and movement cause hairs to move. Nerves send information about body position to brain and allow body to make adjustments in balance.

Care of the Ears 1. Clean outer ears only with a cotton swab. 2. Protect from cold. 3. Avoid loud noises by: Wearing ear protectors when operating loud machinery. Keeping volume low when listening to music.

Ear Problems 1. Deafness is a complete or partial inability to hear. 2. Two kinds of deafness are common: A. Conductive deafness because sound waves are not passed through ear properly. Causes include: Buildup of fluid from ear infection, hardened wax Otosclerosis: a hereditary disorder in which an overgrowth of bone causes the ossicles to lose their ability to move.

B. Sensorineural Deafness Sounds that reach the inner ear do not reach the brain. Damage to the cochlea, auditory nerve, or part of the brain. Prolonged exposure to loud noise Certain types of medicines Increased fluid pressure in the labyrinth Viral infections Tumors

Tinnitus – a condition in which a ringing, buzzing whistling, hissing, or other noise is heard in the ear in the absence of external sound. Overexposure to loud noise.