The Ear : Listen Up!

• Structures of the outer ear
  • Auricle : the "ear," the shell-shaped projection around the external auditory canal
  • External auditory canal (meatus) : extends from the auricle to the tympanic membrane
  • Tympanic membrane : the eardrum; boundary between the outer and middle ears. Sound waves vibrate it.
• Structures of the middle and inner ear
  • Auditory ossicles : the malleus is vibrated by sound waves on the eardrum, which in turn transfers the vibration to the incus, which in turn vibrates the stapes. The base of the stapes is attached to the oval window.
  • Labyrinth : the inner ear, divided into the perilymph-filled bony labyrinth and the membranous labyrinth, which floats in the perilymph and is filled with endolymph
  • Vestibule : contains the saccule and the utricle, which are united by a small duct. The saccule leads into the cochlea and the utricle leads into the semicircular canals. They house maculae, which are equilibrium receptors that respond to gravity.
  • Semicircular canals : are part of equilibrium sense organs. The ampullae are contained within, which house rotational receptors called the crista ampularis.
  • Cochlea : the "snail," has the spiral cochlear duct running through the middle. The organ of Corti, the actual hearing organ, is located within the duct.

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