malleus

The malleus, commonly called the hammer bone, is one of the three auditory ossicles in the middle ear. It is the outermost bone in the tympanic cavity and forms part of the chain that conveys sound vibrations from the tympanic membrane to the inner ear.

Anatomy and connections: The malleus has a head, a neck, and a long handle called the manubrium. The handle is embedded in the fibrous layer of the tympanic membrane near the umbo. A lateral process extends toward the tympanic wall, and the head articulates with the incus at the incudomalleolar joint, linking to the stapes and the inner ear.

Function: The malleus transmits mechanical vibrations from the eardrum to the incus, contributing to the middle ear’s impedance-matching function. Through this dynamic interaction with the adjacent ossicles, it helps convert and deliver sound energy efficiently to the inner ear.

Development and evolution: The malleus and incus originate from the first pharyngeal arch (Meckel’s cartilage) during embryonic development, while the stapes arises from the second arch (Reichert’s cartilage). This arrangement forms the mammalian auditory ossicular chain, optimized for air conduction.

Clinical notes: Injury or disease affecting the malleus, such as temporal bone fracture or chronic otitis media, can cause conductive hearing loss. Disorders of the ossicular chain may be managed conservatively or treated with surgery (ossiculoplasty) to restore sound conduction.