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Noise damage to cells of the organ of Corti.
Semin Hear 1988 Nov; 9(4):267-277
Studies on noise induced morphological and microanatomical changes in cells of the human cochlea were reviewed, analyzing early studies of the organ of Corti using light microscopy and current studies based on scanning electron microscopy and transmission electron microscopy. Studies have indicated that the hair cells of the organ of Corti are arranged as outer rows (OHC) and inner rows (IHC); the IHC have two to three rows of stereocilia and the OHC to have three to four rows of stereocilia. Hearing loss resulted due to loss of hair cell bodies and stereocilia, when the ear was subjected to prolonged noise exposure. The earlier view of the organ of Corti as a passive transducer of acoustic stimuli to neural impulses was revised. The presence of actin and myosin confirmed the ability of hair cells and stereocilia to respond to external stimuli by changing their mechanical properties. Metabolic exhaustion was thought to play a greater role than mechanical effects in causing cochlear cell injury. Damage along the basilar membrane was related to the physical properties of noise, such as frequency. Sound intensity affected the amplitude of basilar membrane displacement. High frequency sound affected the basal part of the cochlea, but low frequency sound stimulated a greater part of it and could therefore produce more widespread damage. The presence of a phalangeal scar in the space formerly occupied by the hair cell was confirmation of hair cell loss. Gross deformations were also noted in association with acoustic trauma. Ciliary damage was thought to result in the loss of ability of the hair cells to excite the auditory nerve, resulting in permanent shifts in hearing threshold. Continued exposure to hazardous noise levels could spread destruction to the full population of hair cells. The author stresses that every effort should be made to preserve human auditory ability, since humans are unable to regenerate lost hair cells.
NIOSH-Author; Acoustic-trauma; Anatomy; Cell-alteration; Cell-damage; Cell-metabolism; Microscopic-analysis; Noise-induced-hearing-loss; Noise-levels
Issue of Publication
Seminars in Hearing
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division