The ''malleus'', or hammer, is a hammer-shaped small bone or

ossicle The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossicu ...

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 (malleus, incus, and stapes), which transfer the vibrations ...

. It connects with the

incus The ''incus'' (: incudes) or anvil in the ear is one of three small bones (ossicles) in the middle ear. The incus receives vibrations from the malleus, to which it is connected laterally, and transmits these to the stapes medially. The incus i ...

, 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 changes in pres ...

. The word is Latin for 'hammer' or 'mallet'. It transmits the sound vibrations from the eardrum 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 irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossi ...

, and attached to the

(tympanic membrane). The head of the malleus is the large protruding section, which attaches to the

. 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 transient structures seen in the Animal embryonic development, embryonic development of humans and other vertebrates, that are recognisable precursors for many structures. In fish, t ...

along with the ''

''. In humans it grows from

Meckel's cartilage In humans, the cartilaginous bar of the mandibular arch is formed by what are known as Meckel's cartilages (right and left; also known as Meckelian cartilages), above which the incus and malleus are located. Meckel's cartilage arises from the fir ...

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 the ...

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

Clinical significance

The malleus may be palpated by

surgeon In medicine, a surgeon is a medical doctor who performs surgery. Even though there are different traditions in different times and places, a modern surgeon is a licensed physician and received the same medical training as physicians before spec ...

s during

ear surgery Otorhinolaryngology ( , abbreviated ORL and also known as otolaryngology, otolaryngology–head and neck surgery (ORL–H&N or OHNS), or ear, nose, and throat (ENT)) is a surgical subspecialty within medicine that deals with the surgical an ...

. 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 morphology concerned with the study of the internal 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 scien ...

and

philosopher Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...

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

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 tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the ...

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 o ...

, 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 Otorhinolaryngology Otology Middle ear