ossiclesmalleus

The malleus, commonly called the hammer, is one of the three auditory ossicles in the middle ear, alongside the incus (anvil) and stapes (stirrup). It forms the outer link in the chain that transmits sound vibrations from the eardrum to the inner ear.

The malleus consists of a handle (manubrium), a neck, head, and a small articular facet that connects with the incus. The handle attaches to the inner surface of the tympanic membrane near the umbo, thereby transducing vibrations from the eardrum to the ossicular chain.

Developmentally, the malleus arises from Meckel's cartilage of the first pharyngeal arch and ossifies through endochondral processes during fetal life. The incus shares this origin, while the stapes derives from Reichert's cartilage of the second arch.

Functionally, the malleus participates in impedance matching, transmitting and transforming the tympanic membrane’s vibrations into the ossicular chain. The articulation with the incus and the lever action of the chain increase pressure transmitted to the oval window of the cochlea, enhancing auditory sensitivity.

Muscles and innervation: the middle ear contains the tensor tympani, which attaches to the malleus handle, and the stapedius, which attaches to the stapes. The tensor tympani is innervated by the mandibular branch of the trigeminal nerve (CN V), and the stapedius by the facial nerve (CN VII). The malleus itself has no separate muscular innervation.

Clinical relevance: disruption of the malleus or its joints, due to trauma or chronic otitis media, can cause conductive hearing loss. Ossiculoplasty and related procedures may repair or replace ossicles to restore hearing.