The ''incus'' (: incudes) or anvil in the

ear In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear co ...

is one of three small

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

s (

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 ...

) in 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 ...

. The incus receives vibrations from the

malleus The ''malleus'', or hammer, is a hammer-shaped small bone or ossicle of the middle ear. It connects with the incus, and is attached to the inner surface of the eardrum. The word is Latin for 'hammer' or 'mallet'. It transmits the sound vibra ...

, to which it is connected laterally, and transmits these to the

stapes The ''stapes'' or stirrup is a bone in the middle ear of humans and other tetrapods which is involved in the conduction of sound vibrations to the inner ear. This bone is connected to the oval window by its annular ligament, which allows the f ...

medially. The incus is named for its resemblance to an

anvil An anvil is a metalworking tool consisting of a large block of metal (usually Forging, forged or Steel casting, cast steel), with a flattened top surface, upon which another object is struck (or "worked"). Anvils are massive because the hi ...

().

Structure

The incus is the second of three

, very small bones in the

which act to transmit sound. It is shaped like an

, and has a long and short crus extending from the body, which articulates with the

. The short crus attaches to the

posterior ligament of the incus The posterior ligament of the incus is a fibrous band that connects the tip of the short crus of the incus to the fossa incudis, running to the mastoid (posterior wall of the middle ear chamber). The posterior incudal ligament plays an importa ...

. The long crus articulates with the

at the lenticular process. The

superior ligament of the incus The superior ligament of the incus is a fibrous band that crosses from the body of the incus to the roof of the tympanic cavity just posterior to the superior ligament of the malleus The ''malleus'', or hammer, is a hammer-shaped small bone ...

attaches at the body of the incus to the roof of the

tympanic cavity The tympanic cavity is a small cavity surrounding the bones of the middle ear. Within it sit the ossicles, three small bones that transmit vibrations used in the detection of sound. Structure On its lateral surface, it abuts the external audit ...

. The incus is homologous to the

quadrate bone The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids ( reptiles, birds), and early synapsids. In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms up ...

found in other tetrapods.

Function

Vibrations in the

are received via 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 changes in pressur ...

. The malleus, resting on the membrane, conveys vibrations to the incus. This in turn conveys vibrations to the

History

"Incus" means "anvil" in Latin. Several sources attribute the discovery of the incus to the anatomist and philosopher

Alessandro Achillini Alessandro Achillini (''Latin'' Alexander Achillinus; 20 or 29 October 1463 (or possibly 1461)2 August 1512) was an Italian philosopher and physician. He is known for the anatomic studies that he was able to publish, made possible by a 13th-centu ...

. The first brief written description of the ''incus'' was by Berengario da Carpi in his ''Commentaria super anatomia Mundini'' (1521).

Andreas Vesalius Andries van Wezel (31 December 1514 – 15 October 1564), latinized as Andreas Vesalius (), was an anatomist and physician who wrote '' De Humani Corporis Fabrica Libri Septem'' (''On the fabric of the human body'' ''in seven books''), which is ...

, in his ''

De humani corporis fabrica ''De Humani Corporis Fabrica Libri Septem'' (Latin, "On the Fabric of the Human Body in Seven Books") is a set of books on human anatomy written by Andreas Vesalius (1514–1564) and published in 1543. It was a major advance in the history of a ...

'', was the first to compare the second element of the ossicles to an anvil, thereby giving it the name ''incus''. The final part of the long limb was once described as a "fourth ossicle" by

Pieter Paaw Pieter is a male given name, the Dutch form of Peter. The name has been one of the most common names in the Netherlands for centuries, but since the mid-twentieth century its popularity has dropped steadily, from almost 3000 per year in 1947 t ...

in 1615.

Additional images

File:Illu auditory ossicles-en.svg, Ossicles File:Occipital bone dissection.jpg, Tympanic cavity. Facial canal. Internal carotid artery. File:Slide1ghe.JPG, Auditory ossicles. Tympanic cavity. Deep dissection. File:Slide2ghe2.JPG, Aditory ossicles. Incus and malleus. Deep dissection.

References

External links

The Anatomy Wiz
''Incus'' {{Authority control Bones of the head and neck Auditory system Ear Ossicles Otorhinolaryngology Otology Middle ear