Vestibular apparatus: maculae, cristae and otoliths !
- Organ
The balance organ of the inner ear: small patches of hair cells that feel gravity and tilting, and crests that feel the head turning.
Updated 2026-11-01
See it in 3D: Semicircular canals · Vestibule · Cochlea
What it is
The vestibular part of the membranous labyrinth has five sensory patches: the maculae of the utricle and saccule, and one crista ampullaris in the ampulla of each of the three semicircular ducts. All use the same hair cells, each with rows of stereocilia and one kinocilium, bathed in potassium-rich endolymph. Maculae carry a heavy layer of calcium carbonate crystals (otoliths) and sense gravity and straight-line acceleration; cristae carry a light gel cupula and sense rotation. Loose otoliths drifting into a canal cause BPPV.
Structure
- Hair cells type I (flask-shaped, wrapped by a nerve calyx) and type II (cylindrical, with bouton endings), between supporting cells.
- Each hair bundle: stereocilia in rows of increasing height next to a single kinocilium; bending toward the kinocilium depolarises.
- Endolymph (high potassium) fills the membranous labyrinth; perilymph (like extracellular fluid) surrounds it.
- Vestibular branch of cranial nerve VIII, with its ganglion (Scarpa) in the internal acoustic meatus.
Maculae vs cristae
| Feature | Maculae (utricle, saccule) | Cristae ampullares |
|---|---|---|
| Location | Wall of the utricle (horizontal) and saccule (vertical) | Ampulla of each semicircular duct |
| Gel layer | Otolithic membrane topped with calcium carbonate otoliths (otoconia) | Cupula: thicker, dome-shaped, no otoliths, spans the ampulla |
| Stimulus | Gravity, head tilt, linear acceleration | Angular (rotational) acceleration |
| How the hair bundle bends | Heavy otoliths lag or slide with gravity | Endolymph lags and pushes the cupula |
| Disorder link | Source of the loose otoconia in BPPV | Affected canal (usually posterior) becomes gravity-sensitive in BPPV |
Clinical notes
- BPPV: brief vertigo with head position changes; otoconia sit in the posterior canal in most cases; repositioning manoeuvres move them back to the utricle.
- Ménière disease: excess endolymph (endolymphatic hydrops) with episodes of vertigo, fluctuating hearing loss, tinnitus and aural fullness.
- Aminoglycosides can destroy vestibular as well as cochlear hair cells.
- Vestibular schwannoma grows from the Schwann cells of the vestibular nerve.
Test yourself
Think of the answer, then tap the question to see it.
What part of the vestibular apparatus detects head rotation?
The crista ampullaris in the ampulla of each semicircular duct, whose hair cells are bent by the cupula when endolymph lags.
How does the cupula differ from the otolithic membrane?
The cupula is thicker, dome-shaped, spans the ampulla and has no otoliths; the otolithic membrane is a thin gel layer loaded with calcium carbonate crystals.
What causes benign paroxysmal positional vertigo?
Otoconia break loose from the utricle and drift into a semicircular canal, usually the posterior, making that crista sensitive to gravity.
Which direction of stereocilia bending depolarises a hair cell?
Bending toward the kinocilium (the tallest side) opens the channels and depolarises the cell.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Inner ear: the cochlea and the organ of Corti
- Cilia, microvilli and stereocilia
- Peripheral nerve: endoneurium, perineurium, epineurium; myelin
Related conditions
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 14.1 Sensory Perception (OpenStax (Rice University), 2022); Balance Disorders (National Institute on Deafness and Other Communication Disorders (NIDCD), 2026).
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Representative model, for educational purposes only.