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Encyclopedia > 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 middle ear contains three ossicles, which amplify vibration of the eardrum into pressure waves in the fluid in the inner ear. The hollow space of the middle ear has also been called the tympanic cavity, or cavum tympani. The eustachian tube joins the tympanic cavity with the nasal cavity (nasopharynx), allowing pressure to equalize between the inner ear and throat. The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. ... Cross section of the cochlea. ... The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ... The inner ear comprises both: the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule. ... The tympanic cavity is a small cavity surrounding the bones of the inner ear. ... Anatomy of the human ear. ... The pharynx is the part of the digestive system of many animals immediately behind the mouth and in front of the esophagus. ...



The function of the middle ear is to efficiently transfer sound energy from air to the liquid contained within the cochlea. Cross section of the cochlea. ...

Contents


Ossicles

The middle ear contains three tiny bones known as the ossicles: malleus, incus, and stapes. The ossicles were given their Latin names for their distinctive shapes; they are also referred to as the hammer, anvil, and stirrup, respectively. The ossicles directly couple sound energy from the ear drum to the oval window of the cochlea. The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ... The malleus is 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. ... This article refers to a bone in the mammalian ear. ... 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. ...


The ossicles mechanically convert the vibrations of the eardrum, into amplified pressure waves in the fluid of the cochlea (or inner ear) by a factor of 1.3. Since the size of the eardrum area is about 17 fold larger than those of the oval window, the sound pressure is concentrated on a smaller area, leading to a total amplification of at least 22. The eardrum is fused to the malleus, which connects to the incus, which in turn connects to the stapes. Vibrations of the stapes footplate introduce pressure waves in the inner ear. The auditory ossicles can also reduce sound pressure(the inner ear is very sensible against overstimulation), by uncoupling each other through particular muscles. The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. ... Cross section of the cochlea. ... The inner ear comprises both: the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule. ... The inner ear comprises both: the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule. ...


The ratio in area between the tympanic membrane and the oval window results in an effective amplification of approximately 14 dB, peaking at a frequency of around 1 kHz. The combined transfer function of the outer ear and middle ear gives humans a peak sensitivity to frequencies between 1 kHz and 3 kHz. The decibel (dB) is a measure of the ratio between two quantities, and is used in a wide variety of measurements in acoustics, physics and electronics. ...


Muscles

The movement of the ossicles may be stiffened by two muscles, the stapedius and tensor tympani, which are under the control of the facial nerve and trigeminal nerve, respectively. These muscles contract in response to loud sounds, thereby reducing the transmission of sound to the inner ear. This is called the acoustic reflex. The facial nerve is seventh of twelve paired cranial nerves. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the middle ear), and other muscles in the floor of the mouth, such as the... The acoustic reflex is an involuntary muscle contraction that occurs in the middle ear of mammals in response to loud sound stimuli. ...


Nerves

Of surgical importance are two branches of the facial nerve which also pass through the middle ear space. These are the horizontal and chorda tympani branches of the facial nerve. Damage to the horizontal branch during surgery can lead to partial, unilateral facial paralysis. The facial nerve is seventh of twelve paired cranial nerves. ...


Comparative anatomy

Mammals are unique in having three ear bones. The incus and stapes develop from bones of the jaw, and allow finer detection of sound.


Some mammals, such as the cat, have an enlarged middle ear encased in a thin, bulbous bone; this structure is known as a bulla. CATS The Musical is a musical composed by Andrew Lloyd Webber (ALW) in 1981 based on Old Possums Book of Practical Cats by T. S. Eliot. ...


Disorders of the middle ear

The middle ear is hollow. If the animal moves to a high-altitude environment, or dives into the water, there will be a pressure difference between the middle ear and the outside environment. This pressure will pose a risk of bursting or otherwise damaging the tympanum if it is not relieved. This is one of the functions of the Eustachian tubes — evolutionary descendants of the gills — which connect the middle ear to the nasopharynx. The Eustachian tubes are normally pinched off at the nose end, to prevent being clogged with mucus, but they may be opened by lowering and protruding the jaw; this is why yawning helps relieve the pressure felt in the ears when on board an aircraft. Anatomy of the human ear. ... In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... The pharynx is the part of the digestive system of many animals immediately behind the mouth and in front of the esophagus. ... Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ... A dog yawning A yawn (synonyms chasma, oscitation from the Latin verb oscitare, to open the mouth wide[1]) is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from lack of stimulation. ...


External links

  • Gray's Anatomy - Middle ear
  • Promenade Around the Cochlea - Middle ear
Sensory system - Auditory system - edit
Outer ear: Pinna | Ear canal 

Middle ear: Eardrum | Ossicles (MalleusIncus & Stapes) | Stapedius | Tensor tympani | Eustachian tube This article or section may be confusing for some readers, and should be edited to be clearer or more simplified. ... The auditory system is the sensory system for the sense of hearing. ... The outer ear is the external portion of the ear and includes the eardrum. ... Juzzah is a loser Boom, Headshot Bergamin and Gerald died The pinna (Latin for feather) is the visible part of the ear that resides outside of the head. ... Anatomy of the human ear. ... The tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. ... The ossicles (also called auditory ossicles) are the three smallest bones in the human body. ... The malleus is 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. ... This article refers to a bone in the mammalian ear. ... 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. ... The stapedius is the smallest striated muscle in the human body. ... The tensor tympani muscle arises from the auditory tube and inserts onto the handle of the malleus, damping down vibration in the ossicles and so reducing the amplitude of sounds. ... Anatomy of the human ear. ...


Inner ear: Cochlea (Scala vestibuliScala media & Scala tympani) | Oval window | Helicotrema | Round window | Basilar membrane | Reissner's membrane | Organ of Corti | Hair cells | Stereocilia The inner ear comprises both: the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule. ... Cross section of the cochlea. ... Scala vestibuli is a perilymph filled cavity inside the cochlea of the inner ear. ... Scala media is a endolymph filled cavity inside the cochlea, located in between the scala tympani and the scala vestibuli, separated by the basilar membrane and Reissners membrane(the vestibular membrane) respectively. ... Scala tympani is the name of one of the perilymph filled cavities in the cochlear labyrinth. ... The helicotrema is the part of the cochlear labyrinth where the scala tympani and the scala vestibuli meet. ... The round window is one of two membranes that separates the inner ear from the middle ear. ... Cross section of the cochlea. ... Reissners membrane is a membrane inside the cochlea of the inner ear, it separates scala media from scala vestbuli and together with the basilar membrane it creates a compartment in the cochlea filled with perilymph, which is important for the function of the organ of Corti inside the scala... The organ of Corti is the organ in the inner ear of mammals that contains auditory sensory cells, or hair cells. // Structure and function It has highly specialized structures that respond to fluid-borne vibrations in the cochlea with a shearing vector in the hairs of some cochlear hair cells. ... Hair cells are the sensory cells of both the auditory system and the vestibular system in all vertebrates. ... Stereocilia are mechanosensing organelles of hair cells, which respond to fluid motion or fluid pressure changes in numerous types of animals for various functions, primarily hearing. ...


Brain: Cochlear nerve VIII → Cochlear nuclei → Superior olivary nuclei → Inferior colliculi → Medial geniculate nuclei → Primary auditory cortex Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... The Cochlear nerve (n. ... The vestibulocochlear nerve is the eighth of twelve cranial nerves and also known as the auditory nerve. ... The cochlear nuclei consist of: (a) the lateral cochlear nucleus, corresponding to the tuberculum acusticum on the dorso-lateral surface of the inferior peduncle; and (b) the ventral or accessory cochlear nucleus, placed between the two divisions of the nerve, on the ventral aspect of the inferior peduncle. ... // Anatomy The superior olivary nucleus (or superior olive) is a small mass of gray substance situated on the dorsal surface of the lateral part of the trapezoid body. ... The paired inferior colliculi together with the superior colliculi form the eminences of the corpora quadrigemina. ... The medial geniculate nucleus is a nucleus of the thalamus that acts as a relay for auditory information. ... The primary auditory cortex is the region of the brain that is responsible for processing of auditory (sound) information. ...


  Results from FactBites:
 
X. The Organs of the Senses and the Common Integument. 1d. 2. The Middle Ear or Tympanic Cavity. Gray, Henry. 1918. ... (2118 words)
The middle ear or tympanic cavity is an irregular, laterally compressed space within the temporal bone.
The tympanic cavity is bounded laterally by the tympanic membrane; medially, by the lateral wall of the internal ear; it communicates, behind, with the tympanic antrum and through it with the mastoid air cells, and in front with the auditory tube (Fig.
It is placed at the bottom of a funnel-shaped depression and, in the macerated bone, leads into the cochlea of the internal ear; in the fresh state it is closed by a membrane, the secondary tympanic membrane, which is concave toward the tympanic cavity, convex toward the cochlea.
Middle Ear Infections (1859 words)
Typically, when the doctor refers to an ear infection, he or she is most likely talking about "acute otitis media" (although there's also the common ear infection called swimmer's ear, or otitis externa).
Ear infections also occur more commonly in boys than girls, in children whose families have a history of ear infections, and more often in the winter season when upper respiratory tract infections or colds are most frequent.
Ear infections are also frequently associated with upper respiratory tract infections and, therefore, with their common signs and symptoms, such as a runny or stuffy nose or a cough.
  More results at FactBites »

 
 

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