The term "primordial utricle" refers to a structure found in the inner ear, which plays a crucial role in balance and spatial orientation. Synonyms for this term include "otolithic membrane", "saccule", and "otolith organ". The otolithic membrane is a sensory structure composed of tiny calcium carbonate crystals called otoliths. These crystals move in response to gravity, detecting changes in head position and acceleration. The saccule is a small sac-like structure that forms part of the vestibular system and contains the otolithic membrane. The term "otolith organ" refers to the sensory organs in the inner ear that detect linear acceleration and gravity, comprising both the saccule and utricle.