Editing Ear (section)

==Structure==
The human ear consists of three parts—the [[outer ear]], [[middle ear]] and [[inner ear]].<ref name="GRAYS40TH_36">{{cite book|last1=Standring|first1=Susan|editor1-last=Borley|editor1-first=Neil R.|title=Gray's Anatomy: The Anatomical Basis of Clinical Practice|date=2008|publisher=[[Churchill Livingstone]]/[[Elsevier]]|location=[[Edinburgh]]|isbn=978-0-443-06684-9|edition=40|pages=Chapter 36. "External and middle ear", 615–631|url=https://books.google.com/books?id=kvhkPQAACAAJ}} [https://archive.org/stream/GraysAnatomy40thEd_201403/Gray's%20Anatomy%20-%2040th%20Ed_djvu.txt Alt URL]</ref> The [[ear canal]] of the outer ear is separated from the air-filled [[tympanic cavity]] of the middle ear by the [[eardrum]]. The middle ear contains the three small bones—the [[ossicles]]—involved in the transmission of sound, and is connected to the [[throat]] at the [[nasopharynx]], via the [[pharyngeal opening of auditory tube|pharyngeal opening]] of the [[Eustachian tube]]. The inner ear contains the [[otolith]] organs—the [[utricle (ear)|utricle]] and [[saccule]]—and the [[semicircular canal]]s belonging to the [[vestibular system]], as well as the [[cochlea]] of the [[auditory system]].<ref name="GRAYS40TH_36" />

===Outer ear===
{{main|Outer ear}}
The outer ear is the external portion of the ear and includes the fleshy visible [[Auricle (anatomy)|auricle]], the ear canal, and the outer layer of the eardrum (also called the tympanic membrane).<ref name="GRAYS40TH_36" /><ref name=GRAYS2005>{{cite book|last=Drake|first=Richard L.|title=Gray's anatomy for students|year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0|pages=855–856|author2=Vogl, Wayne |author3=Tibbitts, Adam W.M. Mitchell  |author4=illustrations by Richard |author5= Richardson, Paul }}</ref>

The auricle consists of the curving outer rim called the [[helix (ear)|helix]], the inner curved rim called the [[antihelix]], and opens into the ear canal. The [[tragus (ear)|tragus]] protrudes and partially obscures the ear canal, as does the facing [[antitragus]]. The hollow region in front of the ear canal is called the concha. The ear canal stretches for about 1{{Nbsp}}inch (2.5{{Nbsp}}cm). The first part of the canal is surrounded by [[cartilage]], while the second part near the eardrum is surrounded by [[bone]]. This bony part is known as the [[auditory bulla]] and is formed by the [[tympanic part of the temporal bone]]. The ear canal ends at the external surface of the eardrum, while the surrounding skin contains [[ceruminous gland|ceruminous]] and [[sebaceous gland]]s that produce protective [[earwax]].<ref name="GRAYS2005" /> Earwax naturally migrates outward through ear canal, constituting a self-cleaning system.<ref name="Shmerling 2017 i652">{{cite web |last=Shmerling |first=Robert H. |date=2017-05-17 |title=3 reasons to leave earwax alone |url=https://www.health.harvard.edu/blog/3-reasons-to-leave-earwax-alone-2017051711718 |access-date=2023-07-11 |website=Harvard Health}}</ref><ref name="Keck Medicine of USC 2022 s129">{{cite web |date=2022-09-29 |title=Why Do I Have So Much Earwax? |url=https://internalmedicine.usc.edu/blog/why-do-i-have-so-much-earwax/ |access-date=2023-07-11 |website=Keck Medicine of USC}}</ref><ref name="HealthLink BC 2021 t871">{{cite web |date=2021-07-01 |title=Earwax |url=https://www.healthlinkbc.ca/health-topics/earwax |access-date=2023-07-11 |website=HealthLink BC}}</ref><ref name="MyHealth.Alberta.ca 2023 a639">{{cite web |date=2023-07-11 |title=Earwax |url=https://myhealth.alberta.ca/Health/Pages/conditions.aspx?hwid=earwx |access-date=2023-07-11 |website=MyHealth.Alberta.ca |ref={{sfnref | MyHealth.Alberta.ca | 2023}}}}</ref>

Two sets of muscles are associated with the outer ear: the [[Outer ear#Intrinsic muscles|intrinsic]] and [[Outer ear#Extrinsic muscles|extrinsic]] muscles. In some mammals, these muscles can adjust the direction of the pinna.<ref name= GRAYS2005 /> In humans, these muscles have little or no effect.<ref name=Moore>{{cite book|vauthors=Moore KL, Dalley AF, Agur AM |date=2013|title=Clinically Oriented Anatomy, 7th ed.|publisher=Lippincott Williams & Wilkins|pages=848–849|isbn=978-1-4511-8447-1}}</ref> The ear muscles are supplied by the [[facial nerve]], which also supplies sensation to the skin of the ear itself, as well as to the external ear cavity. The [[great auricular nerve]], [[auricular branch of vagus nerve|auricular nerve]], [[auriculotemporal nerve]], and [[lesser occipital nerve|lesser]] and [[greater occipital nerve]]s of the [[cervical plexus]] all supply sensation to parts of the outer ear and the surrounding skin.<ref name= GRAYS2005 />

The auricle consists of a single piece of [[elastic cartilage]] with a complicated relief on its inner surface and a fairly smooth configuration on its posterior surface. A [[tubercle (anatomy)|tubercle]], known as [[Darwin's tubercle]], is sometimes present, lying in the descending part of the helix and corresponding to the ear-tip of mammals. The [[earlobe]] consists of [[loose connective tissue|areola]] and [[adipose tissue]].<ref>Stenström, J. Sten: Deformities of the ear; In: Grabb, W., C., Smith, J.S. (Edited): "Plastic Surgery", Little, Brown and Company, Boston, 1979, {{ISBN|0-316-32269-5}} (C), {{ISBN|0-316-32268-7}} (P)</ref> The symmetrical arrangement of the two ears allows for the [[sound localization|localisation of sound]]. The brain accomplishes this by comparing [[interaural time difference|arrival-times]] and [[intensity (physics)|intensities]] from each ear, in circuits located in the [[superior olivary complex]] and the [[Trapezoid body|trapezoid bodies]], which are connected via pathways to both ears.<ref name="purves">{{cite book|last1=Purves|first1=D.|title=Neuroscience|date=2007|publisher=Sinauer|location=New York|isbn=978-0-87893-697-7|pages=332–336|edition=4th}}</ref>
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===Middle ear===
{{main|Middle ear}}
[[File:Blausen 0330 EarAnatomy MiddleEar.png|thumb|right|350px|The middle ear]]
The middle ear lies between the outer ear and the inner ear. It consists of an air-filled cavity called the [[tympanic cavity]] and includes the three [[ossicles]] and their attaching ligaments; the [[Eustachian tube|auditory tube]]; and the [[round window|round]] and [[oval window]]s. The ossicles are three small bones that function together to receive, amplify, and transmit the sound from the eardrum to the inner ear. The ossicles are the [[malleus]] (hammer), [[incus]] (anvil), and the [[stapes]] (stirrup). The stapes is the smallest named bone in the [[human body|body]]. The middle ear also connects to the upper [[throat]] at the [[nasopharynx]] via the [[pharyngeal opening of auditory tube|pharyngeal opening]] of the Eustachian tube.<ref name=GRAYS2005 /><ref>{{cite book|last1=Mitchell|first1=Richard L. Drake, Wayne Vogl, Adam W.M.|title=Gray's anatomy for students|date=2005|publisher=Elsevier|location=Philadelphia|isbn=978-0-8089-2306-0|page=858}}</ref>

The three ossicles transmit sound from the outer ear to the inner ear. The malleus receives vibrations from sound pressure on the eardrum, where it is connected at its longest part (the manubrium or handle) by a ligament. It transmits vibrations to the incus, which in turn transmits the vibrations to the small stapes bone. The wide base of the stapes rests on the oval window. As the stapes vibrates, vibrations are transmitted through the oval window, causing movement of fluid within the [[cochlea]].<ref name="GRAYS2005" />

The round window allows for the fluid within the inner ear to move. As the stapes pushes the [[secondary tympanic membrane]], fluid in the inner ear moves and pushes the membrane of the round window out by a corresponding amount into the middle ear. The ossicles help amplify sound waves by nearly 15–20 times.<ref name="GRAYS40TH_36" />

===Inner ear===
[[File:Blausen 0329 EarAnatomy InternalEar.png|350px|thumbnail|right|The outer ear receives sound, transmitted through the [[ossicles]] of the middle ear to the [[inner ear]], where it is converted to a nervous signal in the [[cochlear nerve|cochlear]] and transmitted along the [[vestibulocochlear nerve]].]]{{main|Inner ear}}
The inner ear sits within the temporal bone in a complex cavity called the [[bony labyrinth]]. A central area known as the [[vestibule of the ear|vestibule]] contains two small fluid-filled recesses, called the [[Utricle (ear)|utricle]] and [[saccule]]. These connect to the [[semicircular canal]]s and the [[cochlea]]. There are three semicircular canals angled at right angles to each other which are responsible for dynamic balance. The cochlea is a spiral shell-shaped organ responsible for the sense of hearing. These structures together create the [[membranous labyrinth]].<ref name="GRAYS40TH_37">{{cite book|last1=Standring|first1=Susan|editor1-last=Borley|editor1-first=Neil R.|title=Gray's Anatomy: The Anatomical Basis of Clinical Practice|date=2008|publisher=[[Churchill Livingstone]]/[[Elsevier]]|location=[[Edinburgh]]|isbn=978-0-443-06684-9|edition=40|pages=Chapter 37. "Inner ear", 633–650}}</ref>

The bony labyrinth refers to the bony compartment which contains the membranous labyrinth, contained within the temporal bone. The inner ear structurally begins at the oval window, which receives vibrations from the incus of the middle ear. Vibrations are transmitted into the inner ear into a fluid called [[endolymph]], which fills the membranous labyrinth. The endolymph is situated in two vestibules, the utricle and saccule, and eventually transmits to the cochlea, a spiral-shaped structure. The cochlea consists of three fluid-filled spaces: the [[vestibular duct]], the [[cochlear duct]], and the [[tympanic duct]].<ref name="GRAYS2005" /> [[Hair cell]]s responsible for [[transduction (physiology)|transduction]]—changing mechanical changes into electrical stimuli are present in the [[organ of Corti]] in the cochlea.<ref name="GRAYS40TH_37" />

===Blood supply===
The blood supply of the ear differs according to each part of the ear.

The outer ear is supplied by a number of arteries. The [[posterior auricular artery]] provides the majority of the blood supply. The [[anterior auricular branches|anterior auricular arteries]] provide some supply to the outer rim of the ear and scalp behind it. The posterior auricular artery is a direct branch of the external carotid artery, and the anterior auricular arteries are branches from the [[superficial temporal artery]]. The [[occipital artery]] also plays a role.<ref name=GRAYS40TH_37 />

The middle ear is supplied by the mastoid branch of either the [[occipital artery|occipital]] or [[posterior auricular artery|posterior auricular arteries]] and the [[deep auricular artery]], a branch of the [[maxillary artery]]. Other arteries which are present but play a smaller role include branches of the [[middle meningeal artery]], [[ascending pharyngeal artery]], [[internal carotid artery]], and the artery of the [[pterygoid canal]].<ref name=GRAYS40TH_37 />

The inner ear is supplied by the anterior tympanic branch of the maxillary artery; the stylomastoid branch of the posterior auricular artery; the petrosal branch of middle meningeal artery; and the [[labyrinthine artery]], arising from either the [[anterior inferior cerebellar artery]] or the [[basilar artery]].<ref name="GRAYS40TH_37" />