Evolution of the cochlea of the ear, consisting of the scala media, the scala tympani, and the scala vestibuli. Regarding mammals, placental and marsupial cochleae have similar cochlear responses to auditory stimulation as well as DC resting potentials. This leads to the investigation of the relationship between these therian mammals and researching their ancestral species to trace the origin of the cochlea. This spiral-shaped cochlea that is in both marsupial and placental mammals is traced back to approximately 120 million years ago. The development of the most basic basilar papilla (the auditory organ that later evolved into the Organ of Corti in mammals) happened
Cochlea are important in some types of tests for hearing impairment, since they are present when the cochlea is working well, and less so when it is suffering from loss of OHC activity. Gap-junction proteins, called connexins, expressed in the cochlea play an important role in auditory functioning. Mutations in gap-junction genes have been found to cause syndromic and nonsyndromic deafness. Certain connexins, including connexin 30 and connexin 26, are prevalent in the two distinct gap-junction systems found in the cochlea. The epithelial-cell gap-junction network couples non-sensory epithelial cells, while the connective-tissue gap-junction network couples connective-tissue cells. Gap-junction channels recycle potassium