ear drum
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In the
anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual conti ...
of humans and various other
tetrapod Tetrapods (; ) are four-limbed animals constituting the superclass Tetrapoda (). It includes Neontology#Extant taxa vs. extinct taxa, extant and extinct amphibians, reptiles (including dinosaurs and therefore birds), and synapsids (including mam ...
s, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped
membrane Image:Schematic size.jpg, up150px, Schematic of size-based membrane exclusion A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membr ...
that separates the external ear from 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
. Its function is to transmit
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...

sound
from the air to 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 (inner ear), labyrinth (cochlea). The a ...
inside the middle ear, and then to the
oval window The oval window (or fenestra vestibuli) is a membrane-covered opening from the middle ear to the cochlea of the inner ear. Vibrations that contact the tympanic membrane travel through the three ossicles and into the inner ear. The oval window is t ...
in the fluid-filled
cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus (cochlea), modiolus. A core component of the cochlea is the Organ of Corti, ...

cochlea
. Hence, it ultimately converts and amplifies vibration in air to vibration in cochlear fluid. The
malleus The malleus or hammer is a hammer-shaped small bone or ossicle of 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 ossicl ...

malleus
bone bridges the gap between the eardrum and the other ossicles. Rupture or perforation of the eardrum can lead to
conductive hearing loss Conductive hearing loss (CHL) occurs when there is a problem transferring sound wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...
. Collapse or
retraction In academic publishing, a retraction is the action by which a published paper in an academic journal is removed from the journal. Online journals typically remove the retracted article from online access. Procedure A retraction may be initiat ...
of the eardrum can cause conductive hearing loss or
cholesteatoma Cholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process. Cholesteatomas are not cancerous as the name may suggest, but can cause significant problems because of th ...
.


Structure


Orientation and relations

The tympanic membrane is oriented obliquely in the
anteroposterior Standard anatomical terms of location deal unambiguously with the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient ...
, mediolateral, and superoinferior planes. Consequently, its superoposterior end lies lateral to its anteroinferior end. Anatomically, it relates superiorly to the
middle cranial fossa The middle cranial fossa, deeper than the anterior cranial fossa, is narrow medially and widens laterally to the sides of the skull The skull is a bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vert ...
, posteriorly to the
ossicle The ossicles (also called auditory ossicles) are three bone A bone is a Stiffness, rigid tissue (anatomy), tissue that constitutes part of the vertebrate skeleton in animals. Bones protect the various organs of the body, produce red blood cel ...
s and
facial nerve The facial nerve (the labyrinthine segment) is the seventh Cranial nerves, cranial nerve, or simply CN VII. It emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations ...

facial nerve
, inferiorly to the
parotid gland The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the man ...
, and anteriorly to the
temporomandibular joint In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral Synovial joint, synovial articulation between the temporal bone of the skull above and the Human mandible, mandible below; ...

temporomandibular joint
.


Regions

The eardrum is divided into two general regions: the pars flaccida and the
pars tensa In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped biological membrane, membrane that separates the external ear from the middle ear. Its function is to transmit ...
. The relatively fragile pars flaccida lies above the lateral
process A process is a series or set of Action (philosophy), activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that pro ...
of the
malleus The malleus or hammer is a hammer-shaped small bone or ossicle of 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 ossicl ...

malleus
between the notch of Rivinus and the anterior and posterior malleal folds. Consisting of two layers and appearing slightly pinkish in hue, it is associated with
Eustachian tube In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any in ...
dysfunction and
cholesteatoma Cholesteatoma is a destructive and expanding growth consisting of keratinizing squamous epithelium in the middle ear and/or mastoid process. Cholesteatomas are not cancerous as the name may suggest, but can cause significant problems because of th ...
s. The larger pars tensa consists of three layers:
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differe ...

skin
,
fibrous tissue Fiber or fibre (from la, fibra, links=no) is a #Natural fibers, natural or #Man-made fibers, man-made substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineeri ...
, and
mucosa A mucous membrane or mucosa is a membrane Image:Schematic size.jpg, up150px, Schematic of size-based membrane exclusion A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions ...

mucosa
. Its thick periphery forms a fibrocartilaginous ring called the
annulus tympanicus Annulus (or anulus) or annular may refer to: Human anatomy * ''Anulus fibrosus disci intervertebralis An intervertebral disc (or intervertebral fibrocartilage) lies between adjacent vertebrae in the vertebral column The vertebral column, a ...
or Gerlach's ligament. while the central umbo tents inward at the level of the tip of malleus. The middle fibrous layer, containing radial, circular, and parabolic fibers, encloses the handle of malleus. Though comparatively robust, the pars tensa is the region more commonly associated with perforations.


Umbo

The manubrium ( la, handle) of the
malleus The malleus or hammer is a hammer-shaped small bone or ossicle of 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 ossicl ...

malleus
is firmly attached to the medial surface of the membrane as far as its center, drawing it toward the tympanic cavity. The lateral surface of the membrane is thus concave. The most depressed aspect of this concavity is termed the umbo ( la, shield boss).


Nerve supply

Sensation of the outer surface of the tympanic membrane is supplied mainly by the auriculotemporal nerve, a branch of the mandibular nerve (cranial nerve trigeminal nerve, V3), with contributions from the auricular branch of the vagus nerve (vagus nerve, cranial nerve X), the
facial nerve The facial nerve (the labyrinthine segment) is the seventh Cranial nerves, cranial nerve, or simply CN VII. It emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations ...

facial nerve
(cranial nerve VII), and possibly the glossopharyngeal nerve (cranial nerve IX). The inner surface of the tympanic membrane is innervated by the glossopharyngeal nerve.


Clinical significance


Examination

When the eardrum is illuminated during a medical examination, a Cone of Light, cone of light radiates from the tip of the malleus to the periphery in the anteroinferior quadrant, this is what is known clinically as 5 o'clock.


Rupture

Unintentional perforated eardrum, perforation (rupture) has been described in blast injuries and air travel, typically in patients experiencing upper respiratory infection, upper respiratory nasal congestion, congestion that prevents equalization of pressure in the middle ear. It is also known to occur in swimming, Underwater diving, diving (including scuba diving), and martial arts. Patients suffering from tympanic membrane rupture may experience bleeding, tinnitus, hearing loss, or disequilibrium (vertigo). However, they rarely require medical intervention, as between 80 and 95 percent of ruptures recover completely within two to four weeks. The prognosis becomes more guarded as the force of injury increases.


Surgical puncture for treatment of middle ear infections

The pressure of fluid in an infected middle ear onto the eardrum may cause it to rupture. Usually, this consists of a small hole (perforation), which allows fluid to drain out. If this does not occur naturally, a myringotomy (tympanotomy, tympanostomy) can be performed. A myringotomy is a surgery, surgical procedure in which a tiny incision is created in the eardrum to relieve pressure caused by excessive buildup of fluid, or to drain pus from 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 fluid or pus comes from a middle ear infection (otitis media), which is a common problem in children. A tympanostomy tube is inserted into the eardrum to keep the middle ear aerated for a prolonged time and to prevent reaccumulation of fluid. Without the insertion of a tube, the incision usually heals spontaneously in two to three weeks. Depending on the type, the tube is either naturally extruded in 6 to 12 months or removed during a minor procedure. Those requiring myringotomy usually have an obstructed or dysfunctional eustachian tube that is unable to perform drainage or ventilation in its usual fashion. Before the invention of antibiotics, myringotomy without tube placement was also used as a major treatment of severe acute otitis media. In some cases, the pressure of fluid in an infected middle ear is great enough to cause the eardrum to rupture naturally. Usually, this consists of a small hole (perforation), from which fluid can drain.


Society and culture

The Bajau people of the Pacific intentionally rupture their eardrums at an early age to facilitate diving and hunting at sea. Many older Bajau therefore have difficulties hearing.


See also

* Middle ear * Valsalva maneuver to equalize pressure across the eardrum


Additional images

File:Anatomy of the Human Ear en.svg, Anatomy of the human right ear. File:Gray907.png, External and middle ear, right side, opened from the front (coronal section) File:Gray908.png, Horizontal section through left ear; upper half of section File:Gray912.png, The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, and from above File:Gray915.png, Auditory tube, laid open by a cut in its long axis File:Gray919.png, Chain of ossicles and their ligaments, seen from the front in a vertical, transverse section of the tympanum [tympanic cavity] File:Gray909.png, Right eardrum as seen through a speculum File:Normal Left Tympanic Membrane.jpg, This is a normal left eardrum. File:Tympanic membrane viewed by otoscope.png, Tympanic membrane viewed by otoscope File:Traumatic Perforation of the Tympanic Membrane.jpg, The oval perforation in this left tympanic membrane was the result of a slap on the ear File:Subtotal Perforation of the right tympanic membrane.tif, A subtotal perforation of the right tympanic membrane resulting from a previous severe otitis media File:TM RIGHT NORMAL.jpg, A normal human right tympanic membrane (eardrum) File:Frog on leaf with eardrum.jpg, Frog on leaf showing eardrum


References


External links


Diagram at Georgia State University


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