The malleus, or hammer, is a hammer-shaped small bone or ossicle of the

middle ear The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea (of the inner ear). The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the ...

. It connects with the incus, and is attached to the inner surface of the

eardrum In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the ...

. The word is Latin for 'hammer' or 'mallet'. It transmits the sound vibrations from the

to the '' incus'' (anvil).

Structure

The malleus is a bone situated in the middle ear. It is the first of the three

ossicles The ossicles (also called auditory ossicles) are three bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditor ...

, and attached to the

tympanic membrane In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the a ...

. The head of the malleus is the large protruding section, which attaches to the incus. The head connects to the neck of malleus. The bone continues as the handle (or manubrium) of malleus, which connects to the tympanic membrane. Between the neck and handle of the malleus, lateral and anterior processes emerge from the bone. The bone is oriented so that the head is superior and the handle is inferior.

Development

Embryologically, the malleus is derived from the first

pharyngeal arch The pharyngeal arches, also known as visceral arches'','' are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arche ...

along with the '' incus''. It grows from Meckel's cartilage.

Function

The malleus is one of three

in the

which transmit sound from the tympanic membrane (ear drum) to the

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in th ...

. The malleus receives vibrations from the tympanic membrane and transmits this to the incus.

Clinical significance

The malleus may be palpated by

surgeons In modern medicine, a surgeon is a medical professional who performs surgery. Although there are different traditions in different times and places, a modern surgeon usually is also a licensed physician or received the same medical training as ...

during ear surgery. It may become fixed in place due to surgical complications, causing hearing loss. This may be corrected with further surgery.

History

Several sources attribute the discovery of the malleus to the

anatomist Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having it ...

and

philosopher A philosopher is a person who practices or investigates philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit=philosophos, meaning 'lover of wisdom'. The coining of the term has been attributed to the Greek th ...

Alessandro Achillini. The first brief written description of the malleus was by

Berengario da Carpi Jacopo Berengario da Carpi (also known as Jacobus Berengarius Carpensis, Jacopo Barigazzi, Giacomo Berengario da Carpi or simply Carpus; c. 1460 – c. 1530) was an Italian physician. His book "''Isagoge breves''" published in 1522 made him the mo ...

in his ''Commentaria super anatomia Mundini'' (1521). Niccolo Massa's ''Liber introductorius anatomiae'' described the malleus in slightly more detail and likened both it and the incus to little hammers terming them ''malleoli''.

Other animals

The ''malleus'' is unique to mammals, and evolved from a lower jaw bone in basal

amniotes Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are dis ...

called the

articular The articular bone is part of the lower jaw of most vertebrates, including most jawed fish, amphibians, birds and various kinds of reptiles, as well as ancestral mammals. Anatomy In most vertebrates, the articular bone is connected to two oth ...

, which still forms part of the jaw joint in reptiles and birds.

Additional images

References

{{Authority control Auditory system Bones of the head and neck Ear Ossicles