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Anatomy Of Ear

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					ANATOMY OF EAR
          BY
Lt.Col Muhammad Rashid
ANATOMY OF EAR
ANATOMY OF EAR

   External Ear
   Pinna
    – External Auditory Canal
    – Tympanic membrane
   Middle Ear
   Inner Ear
EMBRYOLOGY OF EAR
   PINNA
    – Hillocks from 1st and 2nd pharyngeal arch
   Ext Auditory Meatus
    – 1st Branchial Cleft
    – Fully formed by 28th week
   Tympanic Membrane
    – All the three germ layers
          Mucosal layer by endoderm
          Epithelial layer by ectoderm
          Fibrous layer by mesoderm
EMBRYOLOGY OF EAR

   Middle Ear Middle Ear Cleft
    – Endoderm of tubotympanic recess
    – Arises from partly 1st and 2nd pharyngeal pouches
   Malleus Incus from mesoderm of 1st arch
   Stapes 2nd arch except foot plate ottic capsule
   Membranous Inner Ear
    – Ectoderm in the reigeon hind brain thicken to form
      auditory placode that is invaginated to form otocyst
    – Cochlea fully develops by 20th week
      EXTERNAL EAR
   Auricle
    – Single piece of elastic
      cartilage
    – Skin Closely adherent to
      perichondrium
    – Incisura terminalis
           No Cart b/w Crus of
            helix and tragus
EXTERNAL EAR
   External Auditory Canal
    – 24 mm
    – Extends bottom of concha to tympanic membrane
    – Outer 1/3rd cartilagenous 8mm
           Ceruminous glands,pilosebaceous glands
           Hair
           Fissure of Santorini
    – Inner 2/3RD Bony 16mm
           Isthimus 6mm from Tympanic Membrane
           Anterior Recess
           Foramen Of Huschke
EXTERNAL AUDITORY
CANAL
        TYMPANIC MEMBRANE
   Pars Tensa
    – Most of TM
    – Annulus Tympanicus
    – Tented inwards at Umbo
   Pars Flaccida
    – Not Taut
    – Above the lat. Process of
      malleus
   Obliquely set
   10 mm tall 8-9 mm wide
    0.1 mm thick
   Layers
    – Epithelial
    – Mucosal
    – Fibrous
EXTERNAL EAR
   Nerve Supply
    – Pinna
          Greater Auricular C2 C3
          Lesser Occipital
          Auriculotemporal (V3)
          Vagus(auricular branch)
          Facial Nerve
    – External Aud. Canal
          Auriculotemporal ; Roof & ant wall
          Auricular Br vagus & Facial N ; Post wall & floor
    – Tympanic Membrane
          Auriculotemporal N ; anter half of lateral surface
           Auricular Br Vagus ; Post half of lat surface
          Tympanic Branch of IX N; Medial Surface
MIDDLE EAR

   Middle Ear Cleft
    –   Eustachian tube,aditus and mastoid antrum
    –   Mastoid air cells
    –   Lined with mucous membrane
    –   Filled with air
   Divided Into
    – Mesotympanum
    – Epitympanum
    – Hypotympanum
MIDDLE EAR Contd……

   It Likened to Six sided box
    – Roof : Tegmentympani
    – Floor : Thin Plate of bone
          Separates Middle ear from jugular bulb
    – Ant Wall
          Thin Plate of bone separates middle ear from Int
           Carotid Art.
          Two Openings
             – Upper canal of Tensor Tympani
             – Lower for Eustachian tube
MIDDLE EAR Contd……
   Posterior Wall
    – Pyramid
          Tendon of stapedius
    – Aditus
          Behind the Pyramid
          Connects Attic to Antrum
    – VII N Lies Behind the pyramid
    – Facial Recess
          Depression in post. Wall
          Medially by Vertical part of VII N
          Laterally by Chorda tympani
          Above by fossa incudis
       MIDDLE EAR Contd……
   Medial Wall
    – Fromed by Labyrinth
    – Promontary is bulge due
      basal turn of cochlea
    – Contents
           Oval Window
           Round Window
           Process cochleaformis
           Facial Nerve Canal
           Prominence of lateral
            Semicircular Canal
MIDDLE EAR Contd……

   Laterall Wall
    – Tympanic membrane
    – Scutum the bony outer attic wall
   Ossicles Of Middle Ear
    – Malleus
    – Incus
    – Stapes
     MIDDLE EAR Contd……

   Malleus
    – Head, neck,handle
      ant and Lat Process
    – Head Neck lie in the
      attic
    – Handle lie
      embedded in the
      Fibrous layer of TM
    – Laterall Process
          Att to ant. Post.
           Malleal folds
      MIDDLE EAR Contd……

   Incus
    – Body Short process lie in
      attic
    – Long process hangs
      vertically att to stapes
   Stapes
    – Head Neck ant.
      ,post.Crura foot plate.
    – Conducts sound waves
      to oval window
MIDDLE EAR Contd……
   Intratympanic Muscles
    – Tensor Tympani
          Attatches to neck of malleus
          Tenses the Tympanic Membrane
          Supplied By mandibular Div Of Trigeminal Nerve
    – Stapedius
          Neck of stapes
          Dampen loud sounds
          Facial Nerve
   Nerve Supply To Middle Ear
    – Tympanic Plexus
          Tympanic br of IX N
          Sympathtic Plexus around Int Carotid Art
MIDDLE EAR Contd……

   Mastoid Antrum
    –   Air Containing space
    –   Communicates with attic thru aditus
    –   Roof is formed by tegmen antri
    –   Lateral wall is formed by 1.5 cm thick bone in adult
        .Its externally marked by suprameatal triangle
   Aditus
    – Opening thru which attic communicates with antrum
    – Horizontal canal lies medially while foosa incudis
      laterall to it
MIDDLE EAR Contd……
   Mastoid Air Cell System
    – Well Pneumatized
    – Diploetic
    – Sclerotic
   Location of Mastoid air cells
    –   Zygomatic
    –   Tegmen
    –   Perisinis
    –   Peritubal
    –   Retrofacial
    –   Perilabyrinthine
    –   Tip Cells
    –   Marginal
      INNER EAR

   Bony Labyrinth
    – Vestibule
          Central Chamber
          Laterall wall lies oval
           window
          Medial wall has 2
           recesses
             – Elliptical recess
               utricle
             – Spherical Recess
               saccule
          Below the elliptical
           recess is aqueduct of
           vestibule
             – Endo;ymphatic duct
    INNER EAR
   Semicircular canals
    – They 3 in number
    – Lateral anterior and
      posterior
    – Each canal has an
      ampullated and a non
      ampulated end
    – Crus Commune
   Cochlea
    – Colied Tube 2 ½ turns
    – Central axis called modiolus
    – 3 Compartments
           Scala Vestibuli
           Scala Tympani
           Scala Media
INNER EAR

   Scala Vestibuli & Scala tympani
    –   Filled with perilymph
    –   Communicate with each other at helicotrema
    –   Scala Vestibuli closed by foot plate of stapes
    –   Scala tympani closed by Sec. Tympanic mamb.
    –   Scala Tympani connected to Subarachnoid space
        thru aque duct of cochlea
INNER EAR
   Membranous Labyrinth
    – Cochlear Duct
          Scala Media
          Blind coiled tube
              – Basilar membrane
              – Reissners Membrane
              – Stria Vascularis endolymph secretion
          Length of basilar memb. Increases from basal to apical coil
    – Utricle & Saccule
          Utricle Post part of bony vestibule
          Receive opening of semi circular canals
          Linear Acceleration & Decceleration
          Sensory Epithelium is macula
          Saccule lies anterior to utricle
          Also concerned with linear acceleration
INNER EAR
   Semicircular canals
    –   3 in number
    –   Open in the utricle
    –   Neuroepithelium is crista ampularis
    –   Angular acceleration
   Endolymphatic Duct and Sac
    –   Union of 2 ducts
    –   One each from utricle and saccule
    –   Passes thru vestibular aqueduct
    –   Lies b/w layers of dura in the post surface of
        petrous temporal bone
INNER EAR

   Blood Supply
    – Anterior inferior cerebellar artrey
          Labrynthine artrey
            – Anterior vestibular
            – Common Cochlear
                 Cochlear,posterior vestibular arrtrey

    – Venous drainage thru Internal Auditory
      vein
INNER EAR

				
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