Vasaraluu

Vasaraluu, known in human anatomy as the malleus, is one of the three auditory ossicles of the middle ear. It is the first bone in the ossicular chain and its main role is to convey sound vibrations from the tympanic membrane to the incus, and thus to the inner ear.

Anatomy and connections: The malleus is a small bone, roughly 9 millimeters long. It consists of a handle, or manubrium, that is embedded in the fibrous layer of the tympanic membrane, a neck, and a head that articulates with the incus. It forms a synovial joint with the incus, while the incus and stapes complete the chain to the inner ear.

Development: In human embryology, the malleus and incus arise from the first pharyngeal arch cartilage (Meckel’s cartilage), whereas the stapes originates from the second arch (Reichert’s cartilage).

Function: Along with the incus and stapes, the malleus participates in impedance matching between the air-filled middle ear and the fluid-filled cochlea. The lever action of the three ossicles amplifies and transmits sound energy from the tympanic membrane to the inner ear.

Clinical relevance: Trauma, infection, or disease of the middle ear can disrupt the ossicular chain and cause conductive hearing loss. While otosclerosis most commonly affects the stapes, malleus injuries or dislocation can also contribute to hearing impairment.

Name origin: In Estonian, vasaraluu literally means hammer bone, reflecting its shape; it is the same structure known in anatomy as the malleus.