EAR: MIDDLE EAR CAVITY
Ear is a sensory organ responsible for the reception and transmission of sound. It is divided into three main parts - the outer ear, middle ear cavity, and inner ear.
Middle ear cavity is an air-filled cavity present between the outer ear and inner ear. It plays a crucial role in transmitting sound vibrations from the environment to the inner ear.
Parts of ear:
- Pinna (external ear)
- External auditory meatus
- Middle ear cavity
- Eardrum (tympanic membrane)
- Inner ear
- Cochlea
- Vestibule
- Semicircular canals
Boundaries of middle ear cavity:
- Laterally - Tympanic membrane
- Medially - Oval and round windows
- Superiorly - Epitympanic recess
- Inferiorly - Jugular bulb
Contents of middle ear cavity:
- Eardrum (tympanic membrane)
- Malleus (hammer)
- Incus (anvil)
- Stapes (stirrup)
- Oval and round windows
- Eustachian tube
- Middle ear glands
Features of ear ossicles:
- Malleus:
- Has a long handle (manubrium) and a head at the tip
- Attached to the eardrum
- Transmits vibrations from the eardrum to the incus
- Incus:
- Has a body and a long process
- Attached to the malleus and stapes
- Transmits vibrations from the malleus to the stapes
- Stapes:
- Has a head, neck, and footplate
- Attached to the incus and oval window
- Transmits vibrations from the incus to the inner ear
Applied anatomy of middle ear cavity:
- During mastication, the Eustachian tube opens to equalize the air pressure in the middle ear cavity with the atmospheric pressure.
- During hearing, the eardrum vibrates due to sound waves and transmits these vibrations to the ossicles.
- The ossicles amplify the sound vibrations and transmit them to the oval window.
- The stapes footplate touches the oval window membrane, causing vibrations in the inner ear.
Arrows indicating the sequence of sound transmission:
Sound waves → Pinna → External auditory meatus → Eardrum → Malleus → Incus → Stapes → Oval window → Inner ear → Cochlea → Auditory nerve → Brain