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The canals also contain the crista ampullaris. The receptor cells located in the semicircular ducts are innervated by the eighth cranial nerve, the vestibulocochlear nerve (specifically the vestibular portion). The crista ampullaris itself is a cone-shaped structure, covered in receptor cells called "hair cells".
Each ampulla contains an ampullary crest, the crista ampullaris which consists of a thick gelatinous cap called a cupula and many hair cells. The superior and posterior semicircular ducts are oriented vertically at right angles to each other. The lateral semicircular duct is about a 30-degree angle from the horizontal plane.
As a result, the cupula is deflected opposite the direction of head movement. As the endolymph pushes the cupula, the stereocilia is bent as well, stimulating the hair cells within the crista ampullaris. After a short time of continual rotation however, the endolymph's acceleration normalizes with the rate of rotation of the semicircular ducts.
In the semicircular canals, the hair cells are found in the crista ampullaris, and the stereocilia protrude into the ampullary cupula. Here, the stereocilia are all oriented in the same direction. In the otoliths, the hair cells are topped by small, calcium carbonate crystals called otoconia. Unlike the semicircular ducts, the kinocilia of hair ...
The utricle contains a patch of hair cells and supporting cells called a macula. Similarly, the saccule contains a patch of hair cells and a macula. Each hair cell of a macula has forty to seventy stereocilia and one true cilium called a kinocilium. The tips of these cilia are embedded in an otolithic membrane.
The macula of utricle (macula acustica utriculi) is a small (2 by 3 mm) thickening lying horizontally on the floor of the utricle where the epithelium contains vestibular hair cells that allow a person to perceive changes in latitudinal acceleration as well as the effects of gravity; it receives the utricular filaments of the acoustic nerve.
Kinocilia are present in the crista ampullaris of the semicircular ducts and the sensory maculae of the utricle and saccule. [1] One kinocilium is the longest cilium located on the hair cell next to 40–70 stereocilia. During movement of the body, the hair cell is depolarized when the stereocilia move toward the kinocilium.
The delayed movement of the endolymph bends and activates the cupula. When the cupula bends, the connected stereocilia bend along with it, activating chemical reactions in the hair cells surrounding crista ampullaris and eventually create action potentials carried by the vestibular nerve signaling to the body that it has moved in space.