sensation of angular movements of the head is due to the motion of a fluid called endolymph within the vestibular system located within the temporal bone is a negative space known as the inner ear these interconnected canals make up the bony labyrinth of the vestibular system the portion of the inner ear responsible for balance and the body's sense of position in space the volume of the bony labyrinth is filled with a fluid called perilymph which suspends the membranous labyrinth this membranous labyrinth contains the fluid endolymph the structure of the membranous labyrinth consists of three semicircular ducts positioned in three separate planes anterior posterior and lateral each of the ducts has a widened space called an ampulla where it connects with the utricle within the ampulla is a sensory organ the cristae ampullaris when endolymph moves it pushes the gelatinous cupula that covers the crista ampullaris causing embedded hair cells to bend and send nerve impulses to the brain now we will examine the relative motion of endolymph to that of basic movements of the head to increase clarity spheres will be superimposed in the endolymph to help visualize motion of fluid we will also only address movement within the left vestibular apparatus first let's view axial rotation this movement will be best exemplified in the lateral semicircular duct note that the fluid does not move in sync with the labyrinth as the result of inertia for flexion and extension of the head the anterior duct is the most affected to view endolymph motion in the posterior duct we will show lateral bending of the head as you can see the flow of endolymph is an essential part of the body sense of movement