EAR : EAR ANATOMY, PHYSIOLOGY
EAR : EAR External ear
Middle ear
Internal ear
Ear : Ear
External ear : External ear 1. Auricle or Pinna
Yellow elastic cartilage
Skin is tightly adherent to perichondrium on its lateral surface
Incisura terminalis- no cartilage
Endaural incision-Sx of mastoid and EAC
Source of graft material
2. External auditory canal : 2. External auditory canal
Slide 6 : 24 mm
Pulled upwards, backwards and laterally
Cartilaginous part (lat. 8mm)
Fissures of santorini-parotid and mastoid infections spread
Ceruminous and pilosebaceous glands- infection
Bony part (med 16 mm)
Skin
Isthmus- 6mm lat. to TM, foreign body impaction
Anterior recess – cesspool of discharge !
Foramen of Huschke- parotid infection External auditory canal
Tympanic membrane or the drumhead : Tympanic membrane or the drumhead
Tympanic membrane or the drumhead : Obliquely placed, oval in shape
Pars tensa
Annulus
Umbo
Cone of light
Pars flaccida (Shrapnel’s membrane)
Notch of Rivinus
Three layers Tympanic membrane or the drumhead
External ear : External ear Anatomical relations of EAC
Sagging of posterosuperior part of deeper EAC near TM, in acute mastoiditis
Nerve supply
External ear : Arnold’s nerve (X)
Hitzelberger sign (VII and VIII)
Hypoaesthesia of posterior meatal wall due to VIIth nerve involvement in acoustic neuroma (VIIIth)
Jacobson’s nerve(IX) External ear
Middle ear cleft : Middle ear cleft Middle ear
ET
Mastoid, aditus and antrum
Middle ear cleft : Middle ear cleft
Middle ear cleft: Divisions : Middle ear cleft: Divisions
Slide 14 :
Middle ear cleft : Middle ear cleft Roof
Tegmen tympani, middle cranial fossa
Floor
Jugular bulb, congenital deficiency
Anterior wall
Openings for ET and TT muscle
Internal carotid
MEC: Facial recess : MEC: Facial recess Direct access to middile ear without disturbing poserior canal wall
Slide 17 :
ET : ET Connects
Closed at rest
Infants: shorter, wider, narrower
Slide 19 : Tympanic cavity
Mastoid antrum and aditus : Mastoid antrum and aditus
Mastoid and its air cell system : Mastoid and its air cell system
Korner’s septum: incomplete removal of disease : Korner’s septum: incomplete removal of disease
Ossicles of middle ear : Ossicles of middle ear
Intratympanic muscles : Intratympanic muscles Tensor tympani
Neck of malleus
1st arch muscles, 5th nerve mandibular division
Stapedius
Neck of stapes
2nd arch muscle, 7th nerve
Dampen the sound
Tympanic plexus : Tympanic plexus Tympanic branch of 9th nerve
Sympathetic fibers
Supply: MEC, bony ET, Mastoid
Secretomotor fibers of parotid gland : Frey’s Syndrome
Chorda tympani nerve : Chorda tympani nerve 7th nerve
Between handle of malleus and long process of incus
Taste of ant. 2/3rds of tongue
Secretomotor to sublingual and submaxillary
Bony labyrinth : Bony labyrinth
Slide 28 : Vestibule
Semicircular canal
Cochlea Bony labyrinth
Membranous labyrinth : Membranous labyrinth
Membranous labyrinth : Membranous labyrinth
Slide 31 : Cochlear duct
Organ of corti
Length of basilar membrane increases towards apex
Urticle and saccule
Macula
Linear acceleration , Meniere’s disease
Semicircular ducts
Crista ampularis
Endolymphatic ducts and sac
Meniere’s disease Membranous labyrinth
Blood supply of labyrinth : Blood supply of labyrinth
Slide 33 : Blood supply of labyrinth
Blood supply : Blood supply Independent of blood supply of middle ear
Segmental
Symptom of either segments may present
Development of ear : Development of ear 1st arch
Development of ear : Development of ear
Embryology : Embryology Branchial arches
Branchial clefts and pharyngeal pouches
Pinna: 1ST
EAC: 1ST
MEC: TT Recess
Ossicles: MIF, SS
Mastoid: flat, at birth facial nerve, under skin
Inner ear: hind brain, otic placode, cyst
Embryologic origin of ossicles : Embryologic origin of ossicles
Development of ear : Development of ear Auricle
Presuricular sinus: faulty union between 1st and 2nd arch
EAC
Meatal atresia: recanalization begin from medial end
Cochlea
Developed by 20th week of gestation
Physiology of Ear : Physiology of Ear
Organ of Corti : Organ of Corti
Organ of Corti : Tunnel of corti
Hair cells
Outer
Inner
Tectorial membrane Organ of Corti
Auditory pathway : Auditory pathway
Physiology of hearing : Physiology of hearing Mechanism of hearing
Mechanical conduction
Transduction
Conduction via neural pathways
Middle ear: impedance matching : Middle ear: impedance matching
Transduction : Transduction Travelling wave theory
von Bekesy
Other theories
Frequency localization : Frequency localization
Electrical potentials of chochlea : Electrical potentials of chochlea
Electronic potentials : Electronic potentials Endocochlear: RMP
Cochlear microphonics
Summating potential
CAP From cochlea
Vestibular system : Vestibular system
Hair cells : Hair cells
Macula : Macula
Stimulation of SCC : Stimulation of SCC
Vertigo and dizziness : Vertigo and dizziness Inner ear diseases
Meniere’s disease
Motion sickness
Information mismatch
Labrynthine sedatives
Audiology and acoustics : Audiology and acoustics Sound: vibrating object
Frequency: number of cycles per sec.
Pure tone: single frequency
Complex sound: human voice
Pitch: subjective sensation
Overtones: additional frequencies in complex sounds
Intensity : measure of loudness in Db
Loudness: subjective sensation
Slide 56 : Decibels (dB)
Logarithmic ratio
Noise: aperiodic complex sound
White noise: all freq. in audible range
Masking
Narrow band noise
Audiometry for masking
Speech noise
Speech range
Other : Other SPL
Frequency ranges
Audiometric zero
HL
SL