Anatomy of the Human Ear

Outer Ear Structure

• Pinna (Auricle): visible, cartilaginous structure that collects sound waves
• External Auditory Canal (EAC): narrow tube connecting pinna to eardrum
• Eardrum (Tympanic Membrane): thin, flexible membrane that vibrates with sound waves
• External Auditory Meatus: opening of the EAC to the outside environment

Middle Ear Function

• Eardrum (Tympanic Membrane): vibrates with sound waves, transmitting them to ossicles
• Ossicles: three small bones that amplify sound vibrations
  • Malleus (Hammer)
  • Incus (Anvil)
  • Stapes (Stirrup)
• Middle Ear Cavity: air-filled space containing ossicles and eardrum
• Eustachian Tube: connects middle ear to back of throat, regulating air pressure

Cochlea Anatomy

• Cochlea: spiral-shaped structure responsible for sound processing
• Basilar Membrane: membrane running along the cochlea, vibrating with sound waves
• Hair Cells: sensory cells embedded in basilar membrane, converting vibrations to electrical signals
• Auditory Nerve: carries electrical signals from hair cells to the brain for sound interpretation
• Spiral Ganglion: collection of nerve cells that transmit sound information to the brain

Outer Ear Structure

• The pinna, a visible, cartilaginous structure, collects sound waves.
• The external auditory canal (EAC) is a narrow tube that connects the pinna to the eardrum.
• The eardrum, a thin, flexible membrane, vibrates with sound waves.
• The external auditory meatus is the opening of the EAC to the outside environment.

Middle Ear Function

• The eardrum vibrates with sound waves, transmitting them to the ossicles.
• The three small bones that amplify sound vibrations are the malleus (hammer), incus (anvil), and stapes (stirrup).
• The middle ear cavity is an air-filled space containing the ossicles and eardrum.
• The Eustachian tube connects the middle ear to the back of the throat, regulating air pressure.

Cochlea Anatomy

• The cochlea is a spiral-shaped structure responsible for sound processing.
• The basilar membrane, a membrane running along the cochlea, vibrates with sound waves.
• Hair cells, sensory cells embedded in the basilar membrane, convert vibrations to electrical signals.
• The auditory nerve carries electrical signals from hair cells to the brain for sound interpretation.
• The spiral ganglion is a collection of nerve cells that transmit sound information to the brain.

Middle Ear Function

• The middle ear is an air-filled cavity that plays a crucial role in sound conduction and transmission.
• Its primary function is to amplify sound vibrations by 20-30 times, allowing the eardrum to vibrate more efficiently.
• It transduces sound energy, converting sound vibrations into mechanical energy, which is then transmitted to the inner ear.

Structures Involved in Middle Ear Function

• The eardrum (tympanic membrane) is a thin, transparent membrane that separates the outer ear from the middle ear.
• Ossicles (malleus, incus, and stapes) are three small bones that transmit sound vibrations from the eardrum to the inner ear.
• The malleus (hammer) is attached to the eardrum and transmits vibrations to the incus.
• The incus (anvil) transmits vibrations from the malleus to the stapes.
• The stapes (stirrup) transmits vibrations from the incus to the inner ear through the oval window.

Middle Ear Mechanisms

• Sound conduction occurs when sound vibrations from the eardrum cause the ossicles to vibrate, transmitting these vibrations to the inner ear.
• The acoustic reflex is a protective mechanism that helps regulate loud sounds by reducing the amplitude of vibrations transmitted to the inner ear.

Clinical Relevance

• Middle ear infections (otitis media) can lead to hearing loss, pain, and fever.
• Eardrum perforation can cause hearing loss, vertigo, and tinnitus.
• Ossicular damage can lead to conductive hearing loss.