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The incus or anvil is a
bone A bone is a rigid tissue that constitutes part of the vertebrate skeleton in animals. Bones protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobili ...
in the
middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the fluid and membran ...

middle ear
. The
anvil An anvil is a metalworking tool consisting of a large block of metal (usually forged or cast steel), with a flattened top surface, upon which another object is struck (or "worked"). Anvils are as massive as is practical, because the higher ...
-shaped small bone is one of 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 auditory ...
in the middle ear. The ''incus'' receives vibrations from the
malleus The malleus or hammer is a hammer-shaped small bone or ossicle of the middle ear which 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 vibrations f ...
, 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 animals which is involved in the conduction of sound vibrations to the inner ear. This stirrup-shaped bone is connected to the oval window by its annular ligament, which allows ...
medially. The incus is so-called because of its resemblance to an anvil ( la, Incus).


Structure

The incus is the second of the
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 auditory ...
, three bones in the
middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the fluid and membran ...

middle ear
which act to transmit sound. It is shaped like an
anvil An anvil is a metalworking tool consisting of a large block of metal (usually forged or cast steel), with a flattened top surface, upon which another object is struck (or "worked"). Anvils are as massive as is practical, because the higher ...
, and has a long and short crus extending from the body, which articulates with the
malleus The malleus or hammer is a hammer-shaped small bone or ossicle of the middle ear which 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 vibrations f ...
. 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 important r ...
. The long crus articulates with the
stirrup A stirrup is a light frame or ring that holds the foot of a rider, attached to the saddle by a strap, often called a stirrup leather. Stirrups are usually paired and are used to aid in mounting and as a support while using a riding animal (usuall ...
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. Ear Ligaments {{ligament-stub ...
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 auditory ...
.


Function

Vibrations in the
middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles, which transfer the vibrations of the eardrum into waves in the fluid and membran ...

middle ear
are received via the tympanic membrane. The malleus, resting on the membrane, conveys vibrations to the incus. This in turn conveys vibrations to the
stapes The stapes or stirrup is a bone in the middle ear of humans and other animals which is involved in the conduction of sound vibrations to the inner ear. This stirrup-shaped bone is connected to the oval window by its annular ligament, which allows ...
.


History

"Incus" means "anvil" in Latin. Several sources attribute the discovery of the incus to the anatomist and philosopher Alessandro Achillini. The first brief written description of the ''incus'' was by Berengario da Carpi in his ''Commentaria super anatomia Mundini'' (1521). Andreas Vesalius, in his ''De humani corporis fabrica'', 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 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.


See also

* Hearing * Ear * Ossicles


References


External links


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