SPECIAL SENSE ORGANS The ear Divisions of the ear (cont.) Middle ear Houses ear ossicles—malleus, incus, and stapes Ends in the oval window The auditory (eustachian) tube connects the middle ear to the throat Inflammation called otitis media Inner ear (Figure 9-6) Bony labyrinth filled with perilymph Subdivided into the vestibule, semicircular canals, and cochlea Membranous labyrinth filled with endolymph The receptors for balance in the semicircular canals are called cristae ampullaris Specialized hair cells on the organ of Corti respond when bent by the movement of surrounding endolymph set in motion by sound waves (Figure 9-7)

SPECIAL SENSE ORGANS The taste receptors (Figure 9-8) Receptors are chemoreceptors called taste buds Cranial nerves VII and IX carry gustatory impulses Most pathologists list four kinds of “primary” taste sensations—sweet, sour, bitter, and salty Metallic and umami (meaty) tastes are also unique and may soon be added to the list of “primary” taste sensations Nasal congestion interferes with stimulation of olfactory receptors and thereby dulls taste sensations Gustatory and olfactory senses work together to permit creation of many other taste sensations

SPECIAL SENSE ORGANS The smell receptors (Figure 9-9) Receptors for fibers of olfactory or cranial nerve I lie in olfactory mucosa of nasal cavity Olfactory receptors are extremely sensitive but easily adapt (become fatigued) Odor-causing chemicals initiate a nervous signal that is interpreted as a specific odor by the brain