INTERNAL EAR ::
It is a complex cavity situated in the temporal bone The cavity called bony labyrinth is divided into three parts namely (1) Cochlea (2) Vestibule (3) Semicircular canals with membranous labyrinth lodged in it
The vestibule is situated in the centre and it communicates with all other parts of internal ear The semicircular canals communicate with the vestibule
There are three semicircular canals superior posterior and lateral situated at right angle to each other Each canal has a swelling at one end called ampulla which helps the cerebellum in maintaining equilibrium and the sense of position of the head in relation to the body Semicircular canals inform us of dynamic equilibrium and otolith organ informs us of static equilibrium
The cochlea is a spiral tube twisted on it self two and half -spirals and looks like snailshell The coils are arranged on a central bony pillar with a cone shaped axis called modiolus To this is attached membranous labyrinth filled up with fluid in which the organ of corti is placed which has hair brushes that work like musical instrument called piano
The entire cochlea is divided by membrane along its length into three parallel canals called scala vestibuli scala media and cochlear duct Scala tympani and scala vestibuli are filled with perilymph whereas cochlear duct is filled with endolymph
The vestibulo-cochlear nerve collects the sensations of equilibrium from the vestibular division and that of hearing from the cochlear division The fibres of the auditory nerve reach the special nucleus on the back side of the thalamus and then the cerebral cortex for the final analysis of sound and its meaning
0 Comments