The Malleus (Hammer): Anatomy and Function in Hearing

The Smallest Bones in the Body

The three auditory ossicles in the middle ear are the malleus (hammer), incus (anvil), and stapes (stirrup)—named for their shapes.

Malleus Anatomy

• Head: Articulates with incus (incudomalleolar joint).
• Neck: Attachment for tensor tympani muscle (dampens loud sounds).
• Handle (manubrium): Firmly attached to tympanic membrane (eardrum).
• Lateral process & anterior process: Ligamentous attachments to tympanic cavity walls.

Function in Sound Transmission

1. Sound waves vibrate tympanic membrane.
2. Malleus handle moves → rotates malleus.
3. Head transmits vibration to incus → stapes → oval window → cochlear fluid.
4. Impedance matching: Ossicular lever action + area ratio (eardrum:stapes footplate ~17:1) amplifies pressure ~20× for efficient air-to-fluid energy transfer.

Clinical Relevance

• Ossicular fixation/discontinuity (trauma, cholesteatoma, otosclerosis) → conductive hearing loss.
• Tensor tympani spasm → objective tinnitus.
• Surgical reconstruction (ossiculoplasty) uses prostheses or autologous incus.