Incus

General Information
Latin	Incus
Greek
TA98
TA2
FMA
Details
System	Auditory system
Artery
Vein
Nerve
Lymphatic drainage
Precursor
Function
Identifiers
Clinical significance
Notes

The incus, also known as the anvil, is a small bone in the middle ear that plays a crucial role in the auditory system of mammals. It is one of the three ossicles, the others being the malleus and the stapes. These bones are responsible for transmitting sound vibrations from the air to the fluid-filled cochlea.

Anatomy

The incus is the second ossicle in the chain of three bones in the middle ear. It is located between the malleus, which is attached to the tympanic membrane, and the stapes, which connects to the oval window of the cochlea.

The incus has a body and two limbs:

• The body of the incus articulates with the head of the malleus.
• The short limb projects horizontally backward and is attached to the posterior wall of the tympanic cavity by a ligament.
• The long limb descends vertically and ends in a rounded projection called the lenticular process, which articulates with the head of the stapes.

Function

The primary function of the incus is to transmit sound vibrations from the malleus to the stapes. When sound waves strike the tympanic membrane, they cause it to vibrate. These vibrations are transferred to the malleus, which then transmits them to the incus. The incus, in turn, passes these vibrations to the stapes, which then transmits them to the oval window of the cochlea.

The incus acts as a lever, amplifying the force of the vibrations as they pass from the malleus to the stapes. This amplification is necessary to overcome the impedance mismatch between the air in the ear canal and the fluid in the cochlea.

Development

The incus develops from the first pharyngeal arch during embryonic development. It is derived from the cartilage of the arch, known as Meckel's cartilage. The ossification of the incus begins in the fetal period and continues after birth.

Clinical significance

Damage or dysfunction of the incus can lead to conductive hearing loss. This can occur due to trauma, infection, or congenital malformations. Surgical procedures, such as ossiculoplasty, may be performed to repair or replace the incus to restore hearing.

Also see

• Malleus
• Stapes
• Middle ear
• Tympanic membrane
• Cochlea