Atlas of Human Anatomy by Netter

GUIDE

Head and Neck: Ear

Ear

Is divided into three parts

External ear

Auricle

External acoustic meatus

Middle ear

Tympanic cavity and its contents

Epitympanic recess

Inner ear

Vestibulocochlear organ

Membranous labyrinth

Bony labyrinth

Functions are equilibrium (balance) and hearing

External Ear
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Auricle or pinna

Skin-covered elastic cartilage

Collects sound and directs it to external auditory meatus

Features

Deep depression: concha

Lobule: earlobe

External auditory (acoustic) meatus

From the deepest part of the concha to the tympanic membrane

Through the tympanic part of the temporal bone

Lateral one third is cartilaginous and lined with normal skin

Medial two thirds are bony and lined with thin skin continuous onto tympanic membrane

Ceruminous glands (wax producing) and sebaceous glands found in subcutaneous tissue of lateral one third

Tympanic membrane

Forms medial wall external ear, lateral wall of middle ear

Oval and semitransparent

Covered with thin skin externally and mucous membrane internally

Has shallow, cone-like depression at its center (seen otoscopically) with the umbo at the center of the depression

Lateral process (handle) of the malleus embedded in tympanic membrane and tip extends to the umbo on the internal surface

Pars tensa

Part of membrane below handle of malleus

Contains circular and radial fibers

Pars flaccida

Part of membrane above handle of malleus

Contains no fibers

Moves in response to air vibrations

Transmits vibrations to auditory ossicles of middle ear via handle of malleus

Middle Ear
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Contained within petrous part of temporal bone

Includes tympanic cavity and epitympanic recess

Is connected anteriorly with nasopharynx by pharyngotympanic tube (auditory canal)

Contains

Auditory ossicles (bones of middle ear)

Malleus (hammer)

Incus (anvil)

Stapes (stirrups)

Stapedius and tensor tympani muscles

Chorda tympani nerve

Tympanic plexus (nerves)

Walls of tympanic cavity

Roof

Thin bone-tegmen tympani

Separates tympanic cavity from middle cranial fossa

Floor

Bony

Separates tympanic cavity from superior bulb of internal jugular vein

Medial wall

Separates tympanic cavity from inner ear

Features

a. Promontory: round projection overlying basal turn of cochlea

b. Oval window into which footplate of stapes fits-covered by secondary tympanic membrane