Attached to the semi-circular canals are two joined structures called the UTRICLE and the SACCULE .
These also contain HAIR CELLS and ENDOLYMPH .
Within the endolymph here are OTOLITHS (“ear rocks”) which are calcium deposits.
When you stand perfectly upright, these otoliths fall directly down and bend the HAIR CELLS (a special type of neuron) on the lower cells. When you tip your head to the side, they will stimulate the hairs on that side.
The otoliths stimulate the hair cells to tell you what position your head is in and give you a sense of equilibrium.
Therefore, the HAIR CELLS in this region are receptors for equillibrium and the OTOLITHS are an essential component of this process.
Anatomy and Function of the Otoliths Figure 16.21b