Each cochlea contains about 15,500 hair cells in two distinct types

Evidence

There are two types of hair cell in the organ of Corti, around 3,500 inner hair cells and around 12,000 outer hair cells in each cochlea. At the end of the hair cells are stereocilia, which are bundles of tiny (10 to 50 micrometer-long) hairs, or cilia, and there are around 40 and 140 cilia for each inner and each outer hair cell, respectively. The inner hairs cells lie in a single row along the length of the cochlea, and the outer hairs cells lie in multiple rows toward the center of the basilar membrane, where its vibration tends to be the greatest. The structure above the hair cells, known as the tectorial membrane, supports the stereocilia of the outer hair cells, which are embedded within it, but not the stereocilia of inner hair cells. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 559

Categorization

• DEFINE: Defines the tectorial membrane, stereocilia, and the structural difference between inner and outer hair cells.
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 559