Fig. 11

Scanning electron micrographs of a human cochlea at gestational week 16: a A mid-modiolar cut exposes the fluid compartments Scala media (SM), Scala tympani (ST) and Scala vestibuli (ST) that are all fully developed. Cartilaginous tissue is colored blue and borders the Modiolus (M). b Shows a detailed view of Kölliker’s organ of the middle turn with inner hair cells colored red and outer hair cells colored green. Note the primary cilium that is present in all supporting cells of the sensory epithelium! The basilar membrane is coated with a thick, spongiform layer of mesothelial cells. c The higher magnified view depicts the interior of the evolving tunnel of Corti. Medial efferent fibers span the gap between pillar cells as tunnel crossing fibers (TCF) to provide efferent innervation at the basal pole of outer hair cells (OHC, green). Inner hair cell (IHC) red. d The apical end of an inner hair cell is presented: The terminal web of the cuticular plate (colored yellow) is surrounded by long microvilli. Stereocilia (colored red) show typical arrangement similar to adult vestibular hair cell formation. A kinocilium (colored green) at the distal aspect of the apical hair cell pole is still present, its bulging insertion indicates the position of the basal body underneath. Scale bars (a) 4 mm, (b-c) 40 μm and (d) 4 μm