Figure 249

Diagram of two types of sensory hair cells in the sensory areas of the membranous labyrinth. The type I hair cell has a flask-shaped structure with a rounded base. The base is enclosed in a chalice-like afferent nerve ending that has several synaptic boutons for efferent nerve endings. Note the apical surface specializations of this cell, which include a kinocilium and several stereocilia. The apical cytoplasm contains residual basal bodies. The type II hair cell is cylindrical and possesses several nerve terminals at its base for both afferent and efferent nerve fibers. The apical surface specializations are identical with those of the type I cell.

fixed to the wall of the duct and the endolymph. Bending of the stereocilia in the narrow space between the hair calls and the cupula generates nerve impulses in the associated nerve endings.

The maculae of the saccule and utricle are sensors of gravity and linear acceleration

The maculae of the saccule and the utricle are innervated sensory thickenings of the epithelium that face the endolymph of the saccule and utricle (see Fig. 24.7c). As in the cristae, each macula consists of type I and type II hair cells, supporting cells, and nerve endings associated with the hair cells. The maculae of the utricle and saccule are oriented at right angles to one another. When a per s semicircular s semicircular

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