1. Anatomy of the Sensorineural Mechanism

3. Three main subdivisions of the labyrinth 1.cochlea 2.semicircular canals (vestibular system) 3.vestibule (vestibular system, mainly) The Bony Labyrinth (from Zemlin, 1998)

4. Bony labyrinth: Hard, bony outer shell. Membranous labyrinth: Fully contained inside the bony labyrinth; like a convoluted- shaped water balloon stuff inside the bony labyrinth. (from Minifie, Hixon, & Williams, 1973)

5. Another view of the membranous labyrinth (from Perkins & Kent, 1986)

6. Again with the membranous labyrinth, this time all by itself; i.e., with the entire bony labyrinth stripped away. (from Deutsch & Richards, 1979)

7. Schematic and partially unrolled view of the middle ear and labyrinth showing the scala vestibuli, the scala media (also cochlear duct), and the scala tympani, along with the cochlear fluids (endolymph & perilymph). (adapted from Zemlin, 1998)

8. Cuts through an unrolled and a rolled cochlea (from Deutsch & Richards, 1979)

9. Cut through an unrolled cochlea (from Deutsch & Richards, 1979)

10. Detail of a single cut through the cochlea showing the Organ of Corti, 8 th N fibers entering through a tunnel in the spiral lamina (the habenula perforata), the spiral ligament, and the stria vascularis. (from Deutsch & Richards, 1979)

11. (from Zemlin, Fig. 6- 48) Notice the stria vascularis (also area vascularis) – the only good picture I have of this. The s.v. secretes endolymph. Notice also the spiral ligament, which attaches the b.m. to the bony wall of the cochlea, and the limbus (or limbus spiralis), a fibrous covering of the spiral lamina. modiolus spiral ligament

12. Detail of the Organ of Corti (from Stevens,1951) Any cut through the cochlea will show 1 inner hair cell (IHC) and 3 (sometimes 4) outer hair cells (OHCs). This unit – 1 IHC and 3-4 OHCs is referred to as a hair cell channel. There are about 3000 channels in the human cochlea. (That number will become important later when we discuss cochlear implants.)

17. Electron micrograph of a hair bundle as seen from above. Note: (1) cilia are arranged according to height, (2) cilia are arranged in a very distinctive pattern, variously described as a ‘W’ or sometimes a ‘V’ shape. modiolusspiral ligament

18. modiolus spiral ligament IHCsOHCs

19. The cochlear and vestibular braches of the 8 th cranial nerve (from Deutsch & Richards, 1979)