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In vertebrates, the saccule and utricle together make the otolith organs. Both statoconia and otoliths are used as gravity, balance, movement, and directional indicators in all vertebrates and have a secondary function in sound detection in higher aquatic and terrestrial vertebrates. [3] [4] They are sensitive to gravity and linear acceleration.
This membrane is weighted with calcium carbonate-protein granules called otoliths. The otolithic membrane adds weight to the tops of the hair cells and increases their inertia. The addition in weight and inertia is vital to the utricle's ability to detect linear acceleration, as described below, and to determine the orientation of the head. [3]
The vestibular system, in vertebrates, is a sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance. Together with the cochlea , a part of the auditory system , it constitutes the labyrinth of the inner ear in most mammals .
Over time, there was two changes that occurred in parallel when referring to the evolution of the otolithic membrane. First, otoliths that were present in amphibians and reptiles were replaced by a structurally differentiated otolithic membrane. Second, the spindle-shaped aragonitic otoconia were replaced by calcitic barrel-shaped otoconia.
In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear consists of the auricle and the ear canal.
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. [1] In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts: [2]
A study based on splicing morpholinos to down-regulate MsrB3 expression in zebrafish showed shorter, thinner, and more crowded cilia, as well as small, misplaced otoliths. Several stereocilia also underwent apoptosis. Injection with wild-type MsrB3 mRNA rescued auditory deficits, suggesting MsrB3 helps prevent apoptosis. [15]
After this aggregation, growth, including duplication and segregation of existing neurosensory epithelia, gave rise to new epithelia and can be appreciated by comparing sensory epithelia from the inner ears of different vertebrates and their innervation by different neuronal populations. Novel directions of differentiation were apparently ...