What is the gelatinous material covering each crista called?

The correct answer is the cupula, which refers to the gelatinous structure that overlays the cristae within the inner ear's semicircular canals. The cristae are sensory organs responsible for detecting rotational movements of the head. The cupula provides a vital function by moving in response to the movement of the endolymph fluid that flows within the semicircular canals. When the head rotates, the inertia of the endolymph causes it to lag behind, creating a relative movement that deforms the cupula. This deformation stimulates hair cells located within the cristae, leading to the perception of balance and motion.

Understanding the role of the cupula emphasizes its importance in the vestibular system, which is crucial for maintaining equilibrium. In contrast, the gelatinous matrix is a broader term that might refer to various types of gel-like substances but does not specifically describe the material over the crista. Endolymph is the fluid itself that moves, and stereocilia are the hair-like extensions of the hair cells that detect the movement caused by the deformation of the cupula. Each component plays a distinct role in the sensory process, but the cupula is specifically the gelatinous barrier that facilitates the conversion of fluid movement into neural signals.