Which anatomical structure is primarily involved in sensing angular or rotational movements of the head?

The correct answer is Semicircular canals.

- The semicircular canals are three looped structures located in the inner ear, oriented roughly at right angles to each other.
- Their primary function is to detect angular or rotational movements of the head.
- When the head rotates, the fluid (endolymph) inside these canals moves, which bends hair cells embedded in the ampullae of the canals.
- This mechanical stimulus is then converted into neural signals that inform the brain about the direction and speed of head rotation, helping maintain balance and spatial orientation.

- In contrast, the otolith organs (utricle and saccule) detect linear accelerations and head position relative to gravity, not rotational movements.
- The cochlea is involved in hearing, not vestibular sensation.
- The vestibular nerve transmits information from the vestibular organs (including semicircular canals and otoliths) to the brain but does not itself sense movement.

Reference: Gray's Anatomy, 42nd Edition, Volume 2, Chapter 50