Which part of the inner ear primarily detects horizontal linear movement?

The utricle is the primary structure in the inner ear responsible for detecting horizontal linear movement. It is one of the two otolith organs, the other being the saccule. The utricle is oriented more horizontally, allowing it to effectively sense changes in position and acceleration along the horizontal plane. This function is essential for maintaining equilibrium and spatial orientation during activities such as walking or running.

The utricle contains hair cells embedded in a gelatinous membrane that is weighted with tiny calcium carbonate crystals (otoconia). When the head moves horizontally, gravitational forces cause the otoconia to shift, resulting in a displacement of the gelatinous layer and the hair cells. This activation sends signals to the brain regarding the position and motion of the head, which is critical for balance.

The saccule, while also an otolith organ, is oriented vertically and primarily detects vertical linear movements. The vestibule refers to the overall structure that contains the utricle and saccule but does not itself function to detect movement directly. The cochlea is the part of the inner ear involved in hearing and does not play a role in detecting linear acceleration. Thus, the utricle is specifically designed for detecting horizontal linear accelerations, making it the correct choice for this