AP PSYCHOLOGY

Detailed explanation-1: -Three extracellular fluids have been identified in the cochlea: endolymph, perilymph and intrastrial fluid (Table 1; Wangemann & Schacht, 1996). Endolymph fills scala media of the cochlea (Fig. 1). Intrastrial fluid fills the small extracellular spaces within stria vascularis.

Detailed explanation-2: -Structure of the cochlea. The cochlea contains the sensory organ of hearing. It bears a striking resemblance to the shell of a snail and in fact takes its name from the Greek word for this object. The cochlea is a spiral tube that is coiled two and one-half turns around a hollow central pillar, the modiolus.

Detailed explanation-3: -The cochlea is filled with fluid to help facilitate the hair cells of the cochlea registering vibrations and converting them to sound. The hair cells are not actual hair but are cells with hairlike extensions that float in the fluid of the cochlea.

Detailed explanation-4: -The cochlear tube is formed by three membranous and fluid-filled canals, which are the scala vestibuli (SV most superior and connected with the vestibule), scala media (SM), and scala tympani (ST most inferior and ends at the secondary tympanic membrane and the round window) forming a two-and-a-half spiral structure.

Detailed explanation-5: -The cochlear canals contain two types of fluid: perilymph and endolymph. Perilymph has an ionic composition similar to extracellular fluid found elsewhere in the body (i.e., it is K+-poor and Na+-rich), and it fills the scalae tympani and vestibule.