ENT

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 :

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 26 : Vestibule Semicircular canal Cochlea Bony labyrinth

Membranous labyrinth : Membranous labyrinth

Membranous labyrinth : Membranous labyrinth

Slide 29 : 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 31 : 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

ET : ET Connects Closed at rest Infants: shorter, wider, narrower

Slide 39 : Tympanic cavity

Physiology of Ear : Physiology of Ear

Organ of Corti : 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

Frequency localization : Frequency localization

Electrical potentials of chochlea : Electrical potentials of chochlea

Vestibular system : Vestibular system

Hair cells : Hair cells

Macula : Macula

Stimulation of SCC : Stimulation of SCC