Incus
Encyclopedia
The incus or anvil is the anvil
-shaped small bone
or ossicle
in the
middle ear
. It connects the malleus
to the stapes. It was first described by Alessandro Achillini
of Bologna.
The incus transmits sound vibrations from the malleus
to the stapes.
The incus only exists in mammals, and is derived from a reptilian upper jaw bone
, the quadrate bone
. Embryologically it is derived from the first pharyngeal arch along with the rest of the bones of mastication, such as the maxilla
and mandible.
Anvil
An anvil is a basic tool, a block with a hard surface on which another object is struck. The inertia of the anvil allows the energy of the striking tool to be transferred to the work piece. In most cases the anvil is used as a forging tool...
-shaped small bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
or ossicle
Ossicles
The ossicles are the three smallest bones in the human body. They are contained within the middle ear space and serve to transmit sounds from the air to the fluid-filled labyrinth . The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss...
in the
middle ear
Middle ear
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
. It connects the malleus
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...
to the stapes. It was first described by Alessandro Achillini
Alessandro Achillini
Alessandro Achillini was an Italian philosopher and physician.-Biography:He was born and died in Bologna, and is buried in the Church of Saint Martin there...
of Bologna.
The incus transmits sound vibrations from the malleus
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...
to the stapes.
The incus only exists in mammals, and is derived from a reptilian upper jaw bone
Evolution of mammalian auditory ossicles
The evolution of mammalian auditory ossicles is one of the most well-documented and important evolutionary events, demonstrating both numerous transitional forms as well as an excellent example of exaptation, the re-purposing of existing structures during evolution.In reptiles, the eardrum is...
, the quadrate bone
Quadrate bone
The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids , and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint .- Evolutionary variation :In snakes, the quadrate bone has become elongated...
. Embryologically it is derived from the first pharyngeal arch along with the rest of the bones of mastication, such as the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
and mandible.