Avtor/Urednik		Štiblar-Martinčič, Draga
Naslov		Razvoj ušesa
Tip		članek
Vir		Med Razgl
Vol. in št.		Letnik 46, št. 1
Leto izdaje		2007
Obseg		str. 45-54
Jezik		slo
Abstrakt		The ear consists of three parts that have different origins, but function as one unit. The internal ear originates from the otic vesicle, which is detached from surface ectoderm during the fourth week of development. The vesicle is then divided into a ventral component, which gives rise to the saccule and the cochlear duct, and a dorsal component, which gives rise to the utricle, semicircular canals, and endolymphatic duct. The epithelial structures thus formed are known collectively as the membranous labyrinth. Except for the cochlear duct, which forms the organ of hearing, all other structures derived from the membranous labyrinth compose the organ of balance. Structures of the middle and external ear develop from the structures and derivates of the pharyngeal apparatus. The tympanic cavity and auditory tube derive from the endoderm of the first pharyngeal pouch. The ossicles develop from the mesenchyme of the first (malleus and incus) and second (stapes) pharyngeal arches. The muscles of the middle ear and their nerves derive from the pharyngeal apparatus derivates. The tympanic membrane arises from the mesenchyme covered by the ectodermal epithelium on the outer side, and with the endoderm of the first pharyngeal pouch on the inner side. The external auditory meatus derives from the first pharyngeal groove. The auricle develops from six mesenchymal hillocks along the first and second pharyngeal arch that surround the first pharyngeal groove. The genes responsible for the development of the internal ear are: Pax2, which is responsible for the formation of the cochlear duct, NkxS, which is responsible for the formation of the semicircular ducts, and Notchl, Math1, Jag2, Hes1 and Hes2, which are responsible for the differentiation of sensory hair cells within the hearing and balance organs. The retinoblastoma gene has a distinct role in the maturation of cochlear and vestibular hair cells.
Izvleček		Uho je sestavljeno iz treh delov, ki imajo različne izvore, delujejo pa enotno. Notranje uho izvira iz ušesnega mehurčka, ki se v četrtem tednu razvoja loči od površinskega ektoderma. Na mehurčku je sprednji del, iz katere nastaneta vrečica in polžev vod, in zadajšnji del, iz katerega nastanejo mešiček, polkrožni kanali in endolimfatični vod. Tako nastale vrhnjične strukture tvorijo membranski labirint notranjega ušesa. Razen polževega voda, v katerem se oblikuje organ sluha, sestavljajo ostale strukture membranskega labirinta organ ravnotežja. Strukture srednjega in zunanjega ušesa se razvijejo iz žrelnega aparata in njegovih derivatov. Votlina srednjega ušesa in ušesna troblja nastaneta iz endoderma prvega žrelnega žepa. Slušne koščice se razvijejo iz embrionalnega tkiva prvega (kladivce in nakovalce) in drugega (stremence) žrelnega loka. Iz derivatov žrelnega aparata so tudi dve mišici in živci srednjega ušesa. Bobnič nastane iz embrionalnega tkiva, ki ga z zunanje strani pokriva ektodermalna vrhnjica, z notranje strani pa endoderm prvega žrelnega žepa. Zunanji sluhovod nastane iz ektoderma prve žrelne brazde. Uhelj se razvije iz šestih zgostitev embrionalnega tkiva prvega in drugega žrelnega loka okrog prve žrelne brazde. Razvoj srednjega in zunanjega ušesa poteka veliko daljši čas kot razvoj notranjega ušesa. Ob rojstvu so poleg notranjega ušesa dokončno razvite tudi vse strukture srednjega in zunanjega ušesa, razen celice bradavičarja, dolžina zunanjega sluhovoda in velikost uhlja. Geni, odgovorni za razvoj notranjega ušesa, so: gen Pax2, ki je odgovoren za nastanek polža, gen NkxS, ki je odgovoren za nastanek polkrožnih kanalov, ter geni Notchl, Math1, Jag2, Hes1 in Hes2, ki so odgovorni za oblikovanje čutnih celic dlačnic tako slušnega kot ravnotežnega organa. Gen retinoblastom ima ključno vlogo pri dozorevanju dlačnic spiralnega in vestibularnega organa.
Deskriptorji		EAR LABYRINTH EAR, EXTERNAL EAR, MIDDLE DEAFNESS