HIS 120 Structures of the Inner Ear OverviewPresentation Transcript
Structures of the Inner Ear The Labyrinth The inner ear, often referred to as the labyrinth, is composed of two separate physical parts. They are:1. The osseous (bony) portion.2. The membranous portion.
Structures of the Inner Ear Osseous portion Contains the:1. Perilymph fluid2. Cochlea3. Three semicircular canals4. Vestibule
Structures of the Inner Ear Membranous portion Contains the:1. Endolymph fluid2. Saccule3. Utricle4. Cochlear duct
Structures of the Inner Ear The inner ear consists of two major functional parts. They are:1. The vestibular portion (balance)2. The cochlear portion (hearing)
Structures of the Inner Ear The Cochlea It is a fluid filled cavity which is divided into three canals. They are:1. The scala vestibuli2. The scala media (cochlear duct)3. The scala tympani
Structures of the Inner EarFor now, we will focus primarily onthe scala media (cochlear duct). Thisis where the organ of Corti is located.
Structures of the Inner Ear The Organ of CortiThis is where the mechanical soundenergy gets transduced intoelectrochemical energy.
Structures of the Inner Ear The Organ of CortiIt is located on top of the basilarmembrane and consists ofapproximately one row of 3500 innerhair cells, and three rows of outer haircells (each row containing over 4500hair cells).
Structures of the Inner Ear Inner & Outer hair cellsThere are some excellent photos ofboth inner and outer hair cells inZemlin pages #474 and #475.
Structures of the Inner Ear StereociliaBoth inner and outer hairs cells havestereocilia on top of each hair cell.These stereocilia contact the tectorialmembrane.
Structures of the Inner Ear StereociliaThere are approximately 150stereocilia on top of each outer haircell and 70 stereocilia on top of eachinner hair cell.
Structures of the Inner Ear Inner hair cellsThey contain a chemical make upwhich may aid in the transduction ofmechanical energy intoelectrochemical energy.
Structures of the Inner Ear Inner hair cellsNinety percent of the afferent VIIIthnerve fibers are innervated by theinner hair cells.
Structures of the Inner Ear Outer hair cellsThey resemble muscle fibers,complete with contractile proteins incell bodies, which enables them toactively change shape.
Structures of the Inner Ear Outer hair cellsAs the basilar membrane moves, itserves as an “amplifier” for inner haircell activation.
Structures of the Inner Ear The VIIIth nerveIt moves both afferent and efferentinformation to the cochlear nucleus.Afferent is neural information from theperipheral systems to the brain.Efferent is neural information from thebrain to the peripheral systems.
Structures of the Inner Ear Cochlear blood supplyIs very complex, but primary supplies arearound in the scala media area.The stria vascularis maintains thechemical composition of the endolymph.There are a group of small blood vesselsjust below the basilar membrane whichsupply the organ of Corti with nutrients.
Structures of the Inner Ear Cochlear blood supplyPlease note, there is no direct contactwith the vascular system and thestructures of the cochlea. There is an“intermediate transfer system”through the intracochlear fluids ofeach site.