Ossicles

Information about Ossicles



Ossicles

Chain of ossicles and their ligaments, seen from the front in a vertical, transverse section of the tympanum.
Latin	membrana tympani
	subject #231 1044
MeSH	Ear+Ossicles

The ossicles (also called auditory 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 (cochlea). The absence of the auditory ossicles would constitute a moderate to severe hearing loss.

Studies have shown that ear bones in mammal embryos are attached to the dentary, which is part of the jaw. These are ossified portions of cartilage that are attached to the jaw. This is called Meckel's cartilage. As the embryo develops, the cartilage hardens to form bone. Later in development, the bone structure breaks loose from the jaw and migrates to the inner ear area. The structure is known as the middle ear and is made up of the incus, stapes, malleus, and tympanic. These correspond to the quadrate , preartiluar, articular, and angular structures in the reptile jaw. For this reason, researchers believe the similarity is because of mammals and reptiles sharing a common ancestor.^[1]

The ossicles are, in order from the eardrum to the inner ear, the hammer, anvil, and stirrup, so named because of the shape of the bones. They are also commonly referred to by the equivalent Latin terms: malleus, incus, and stapes respectively.

The malleus articulates with the incus and is attached to the tympanic membrane (eardrum), from which vibrational energy is passed.
The incus is connected to both the other bones.
The stapes articulates with the incus and is attached to the membrane of the fenestra ovalis, the elliptical or oval window or opening between the middle ear and the vestibule of the inner ear.

As sound waves vibrate the tympanic membrane (eardrum), it in turn moves the nearest ossicle, the malleus to which it is attached. The malleus then transmits the vibrations, via the incus, to the stapes, and so ultimately to the membrane of the fenestra ovalis, the opening to the vestibule of the inner ear.

The ossicles give the eardrum mechanical advantage via lever action and a reduction in the area of force distribution; the resulting vibrations would be much smaller if the sound waves were transmitted directly from the outer ear to the oval window. However, the extent of the movements of the ossicles is controlled (and constricted) by certain muscles attached to them (the tensor tympani and the stapedius). It is believed that these muscles can contract to dampen the vibration of the ossicles, in order to protect the inner ear from excessively loud noise (theory 1) and that they give better frequency resolution at higher frequencies by reducing the transmission of low frequencies (theory 2) (see acoustic reflex). These muscles are more highly developed in bats and serve to block outgoing cries of the bats during echolocation (SONAR).

Occasionally the joints between the ossicles become rigid. One condition, Otosclerosis, results in the fusing of the stapes to the oval window. This reduces hearing and may be treated surgically.

External links

The middle ear and the ossicles

• • [ e] Sensory system: Auditory and Vestibular systems
Outer ear	Pinna (Helix, Antihelix, Tragus, Antitragus, Earlobe) • Ear canal
Middle ear	Eardrum • Ossicles (Malleus, Incus & Stapes) • Stapedius • Tensor tympani • Eustachian tube (Torus tubarius)
Inner ear/Labyrinth	Bony labyrinth (Vestibule) • Membranous labyrinth Oval window • Helicotrema • Round window Cochlea: Spiral ganglion • Modiolus • Cochlear duct/scala media (Endolymph, Stria vascularis, Spiral ligament, Organ of Corti) • Scala vestibuli and Scala tympani (Perilymph) Reissner's/vestibular membrane • Basilar membrane • Tectorial membrane Organ of Corti: Hair cells • Stereocilia • Sulcus spiralis (externus, internus) • Limbus spiralis
Vestibular system	Static/translations: Utricle (Macula) - Saccule (Macula, Endolymphatic sac, Endolymphatic duct) - Kinocilium - Otolith Kinetic/rotations: Semicircular canals (Superior, Posterior, Horizontal) • Cupula • Ampullae (Crista ampullaris)
Brain (auditory)	Cochlear nerve ^VIII → Cochlear nuclei → Superior olivary nuclei → Lateral lemniscus → Inferior colliculi → Medial geniculate nuclei → Primary auditory cortex

Human Bones

• • [ e]

References

1. ^ Meng, Jin. "The Journey From Jaw to Ear." Biologist. vol. 50. (2003) p. 154-158.

Latin}}}
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals.
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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.
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Sound is a disturbance of mechanical energy that propagates through matter as a wave (through fluids as a compression wave, and through solids as both compression and shear waves).
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For more uses of the word labyrinth, see Labyrinth (disambiguation)

The labyrinth is a system of fluid passages in the inner ear, including both the cochlea which is part of the auditory system, and the vestibular system which provides the
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The cochlea is the auditory portion of the inner ear. Its core component is the Organ of Corti, the sensory organ of hearing, which is distributed along the partition separating fluid chambers in the coiled tapered tube of the cochlea.
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mandible (from Latin mandibūla, "jawbone") or inferior maxillary bone is, together with the maxilla, the largest and strongest bone of the face . It forms the lower jaw and holds the lower teeth in place.
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Cartilage is a type of dense connective tissue. It is composed of collagen fibers and/or elastin fibers, and can supply smooth surfaces for the movement of articulating bones.
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The cartilaginous bar of the mandibular arch is formed by what are known as Meckel’s cartilages (right and left) ; above this the incus is developed.

The dorsal end of each cartilage is connected with the ear-capsule and is ossified to form the malleus; the ventral
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For the record label, see Incus Records.

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 Achillin of Bologna.
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The stapes or stirrup is the stirrup-shaped small bone or ossicle in the middle ear which attaches the incus to the fenestra ovalis, the "oval window" which is adjacent to the vestibule of the inner ear. It is the smallest and lightest bone in the human body.
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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.
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Quadrate may refer to:

Quadrate bone
Quadrate (heraldry)

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The articular bone is in the lower jaw of most tetrapods, including amphibians, sauropsids ("reptiles"), birds and early synapsids. In these animals it is connected to two other lower jaw bones, the suprangular and the angular; and it forms the jaw joint by articulating with the
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The angular is a large bone in the lower jaw of amphibians, birds and reptiles, which is connected to all other lower jaw bones: the dentary (which is the entire lower jaw in mammals), the splenial, the suprangular, and the articular Also see: Angular momentum.
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For the record label, see Incus Records.

The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. Its function is to transmit sound vibrations from the air, conducted through the external acoustic meatus to the ossicles inside the
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The oval window (or vestibular window) is a membrane-covered opening which leads from the middle ear to the vestibule of the inner ear.

Vibrations arriving at the eardrum are transmitted via the interacting ossicles from the middle ear through the membrane of the
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vestibule is the central part of the osseous labyrinth, and is situated medial to the tympanic cavity, behind the cochlea, and in front of the semicircular canals.

It is somewhat ovoid in shape, but flattened transversely; it measures about 5 mm.
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outer ear is the most external portion of the ear. The outer ear includes the pinnae (also called auricle), the ear canal, and the very most superficial layer of the ear drum (also called the tympanic membrane).
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In physics and engineering, mechanical advantage (MA) is the factor by which a mechanism multiplies the force put into it. Following are simple machines where the mechanical advantage is calculated.

The beam shown is in static equilibrium around the fulcrum.

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The tensor tympani, the larger of the two muscles of the tympanic cavity, is contained in the bony canal above the osseous portion of the auditory tube, from which it is separated by the septum canalis musculotubarii.
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The stapedius is the smallest striated muscle in the human body. At just over one millimeter in length, its purpose is to stabilize the smallest bone in the body, the stapes.
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The acoustic reflex (or stapedius reflex) is an involuntary muscle contraction that occurs in the middle ear of mammals in response to high-intensity sound stimuli.
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Ossicles

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