ANATOMY OF EAR

EXTERNAL EAR MIDDLE EAR INTERNAL EAR1. Auricle2. External Auditory Canal

1. Eustachian tube2. Middle Ear Cavity3. Mastoid Air Cells

1. Cochlea2. Vestibular system

1. EXTERNAL EAR

AURICLE ( PINNA) EXTERNAL AUDITORY CANAL (EAC)formed mainly of CARTILAGE- with perichondrium firmly attached to skin- in continuity with the cartilage of outer part of EAC

Areas without auricular cartilage :1. LOBULE – fat2. Upper part of area between TRAGUS & HELIX – fibrous tissue

- 24mm

OUTER 1/3 CARTILAGENOUS PART INNER 2/3 BONY PARTskin with- short hairs, sebaceous & ceruminous glands *FURUNCULOSIS

skin with- NO hair follicles or glands

runs UPwards & BACKwards runs FORwards & BACKwards

2. MIDDLE EAR CLEFT

EUSTACHIAN TUBE MIDDLE EAR CAVITY MASTOID ANTRUM & AIR CELLS

Tympanic membrane (eardrum)- 1 cm (transverse diameter)- set at acute angle with the floor of EAC inclined forwards & downwards

PARS TENSA PARS FLACCIDA- cone of light located at the lower end of umbo (concave) a small triangular part above the short process of malleus- outer epithelial layer- middle fibrous layer [insertion of short process & handle of malleus]- inner mucosal layer

- outer epithelial layer- inner mucosal layer* NO fibrous layer

- 36 mm- extends from middle ear cavity to nasopharynx inferiorly

in child is- wider- shorter- more pheripheral* infection more in children!

communication =- ant : nasopharynx (thru ET)- post : mastoid anthrum & mastoid air cells

contents =1. 3 ossicular chain = malleus, stapes, incus+ ligaments supporting them2. 2 muscles = tensor tympani, stapedius3. 1 nerve = chorda tympani

- both are contained within the mastoid process

MASTOID PROCESS- 80% : pneumatized with many air cells- 20% : sclerotic with few or no air cells (if contain bone marrow called diploid)

MASTOID ANTRUM- communicate with attic of middle ear thru the aditus

BONY part CARTILAGENOUS partupper 1/3 lower 2/3close to middle ear close to nasopharynx

bony opening always patent (unless obstructed pathologically)

cartilaginous opening is potentially closed & opens only during swallowing & yawning

6 walls Superior Inferior Anterior Posterior Medial Lateral

- tegmen tympani- middle cranial fossa- temporal lobe of brain

- jugular bulb - bony Eustachian tube- canal for tensor tympani muscle- ICA

- aditus ad antrum- vertical part of facial nerve

- horizontal pt of facial nerve- oval window- promontory- round window

- tympanic membrane- scutum

Parts of tympanic cavityEpitympanium (attic) above tympanic membraneMesotympanium opposite tympanic membraneHypotympanium below tympanic membrane