The Human Ear Structure and Function

Outer Ear Structure

• The outer ear consists of:
  • Pinna (auricle): the visible, cartilaginous structure that collects sound waves
  • External auditory canal (EAC): a narrow tube that connects the pinna to the eardrum
  • Eardrum (tympanic membrane): a thin, semi-transparent membrane that separates the EAC from the middle ear

Middle Ear Function

• The middle ear is an air-filled cavity that contains:
  • Three small bones (ossicles):
    • Malleus (hammer)
    • Incus (anvil)
    • Stapes (stirrup)
  • These bones amplify sound vibrations and transmit them to the inner ear
  • The middle ear is connected to the back of the throat by the Eustachian tube, which regulates air pressure

Auditory Nerve Pathway

• Sound vibrations from the middle ear travel through the:
  • Cochlea: a spiral-shaped structure in the inner ear that converts vibrations into electrical signals
  • Auditory nerve (CN VIII): a bundle of nerve fibers that carries electrical signals to the brain
  • The signals are processed in the auditory cortex, where they are interpreted as sound

Bones of the Ear

• The three bones of the middle ear are responsible for sound conduction:
  • Malleus: attached to the eardrum and transmits vibrations to the incus
  • Incus: connected to the malleus and transmits vibrations to the stapes
  • Stapes: attached to the incus and transmits vibrations to the cochlea through the oval window
• These bones work together to amplify sound vibrations and transmit them to the inner ear