External Ear

auricle

Auricle - irregular flap of cartilage, equipped w/ vestigial mm.(innervated by CN7) surrounding ext. auditory meatus

-Parts: tragus helix, lobule

External Ear

External Auditory Meatus

-bounded medially by tympanic membrane

-Bony and cartilaginous wall

-Tympanic membrane: 2 Epithelial layers

Innervation of external ear

Auricle 

-Great auricular n. (cervical plexus) 

-Lesser occipital n. (cervical plexus)

-Auriculotemporal n (CN V3)

Innervation of external ear

meatus and tympanic membrane 

-auriculotemporal n (CN V3)

-Vagus n (CN X)

-Possibly CN 7 and 9

Middle Ear

Overview

-Within temporal bone

-Energy of sound wave is converted into mech. energy through a chain of ossicles.

-Consists of tympanic cavity and contents

-Continuous ant. w auditory tube and post. w mastoid air cells

Tympanic Cavity Boundaries 

Roof, Floor, Lateral wall

-Roof: tegmen typmani 

-Floor: Jugular wall(tympanic n)

-Lateral wall: tympanic membrane 

-Anterior (carotid) wall: 

1.opening of auditory tube

2.tensor tympani muscle

3.internal carotid artery

Tympanic Cavity Bourndaries

Posterior wall, medial wall

-Posterior wall: -aditus to mastoid air cells

-Stapedius M.

-Facial canal

-Medial wall:-oval window(fenestra vestibuli)

-Round Window(Fenestra cochleae)

-Promontory(tympanic plexus)

Contents of Tympanic Cavity

Ossicles:-malleus-attached to tympanic membrane

-incus-intermediate

-stapes- attached to oval window

Muscles: -Tensor tympani m (CNV3)

-stapedius m- (CNVII)

Chorda tympani n. (runs across tympanic mem)

Contents of tympanic cavity 

cont. 

Neurovascular supply:

innervation-tympanic plexus(CN9)

Blood Supply-tympanic branches of maxillary and adjacent aa.

Aditus: opens to mastoid air cells

Auditory tube: opens to nasopharynx, equalizes air pressure in middle ear

Vestibule: central, communicates:

-laterally w middle ear by oval window

-anteriorly w chochlea

-post. w semicircular canals

Chochlea: anterior, responsible for audition.

-round window opens from it

Semicircular canals: superior and lateral to vestibule, responsible for balance

Vestibulocochlear n

CN8

Special sensory fibers only

-cochlear n(hearing)

-vestibular n.(equilibrium)

Exits cranial cavity through internal auditory meatus

-Internal auditory meatus

-facial canal

-Facial nerve branches

1.Geniculate ganglion(sensory only)

2.Greater petrosal nerve

3.Nerve to stapedius

4. Chorda tympani n