An irregularly shaped structure made of elastic cartilage and skin

Superior portion has a skeleton of elastic cartilage

Inferior portion is known as the lobule and has no cartilage

Helix— the outermost curved rim of the auricle, continues anteriorly to blend with the head at the crus helix

Antihelix— the portion of cartilage that follows along the helix from the inside

Scaphoid fossa— the depressed area between the helix and the antihelix

Concha— demarcated by the antihelix, it is the depressed area that leads to the external acoustic meatus

Tragus— extends from the face into the concha

Antitragus— extends from the inferior portion of the antihelix into the concha and is separated from the tragus by the intertragic notch

The passageway connecting the concha of the auricle to the tympanic membrane

Covered by skin rich in sebaceous and cerumen-secreting glands

About 2.5 cm in length

Lateral 1/3— cartilaginous, extends into the temporal bone

Medial 2/3— osseous, formed by the tympanic, squamous, and petrous portions of the temporal bone

The most medial portion of the external ear that separates it from the middle ear

Lies in a groove on the tympanic part of the temporal bone

A thin, semitransparent, 3-layered membrane:

External layer —derived from skin; composed of stratified squamous epithelium

Middle layer —fibrous, with fibers attaching to the malleus

Inner layer —continuous with the mucous membrane of the middle ear cavity; composed of columnar epithelium with cilia

Anterior and posterior malleolar folds lie on the superior portion of the tympanic membrane

Tense and loose portions are called the pars tensa and pars flaccida, respectively

Thin bone separates the middle ear from the internal jugular v.

Tympanic canaliculus, located in the floor of the middle ear; allows the tympanic branch of the glossopharyngeal n. to enter the middle ear

Auditory tube— located in the middle ear’s anterior wall; connects the middle ear with the nasopharynx; equilibrates pressure on either side of the tympanic membrane, and allows proper drainage of the middle ear

Lesser petrosal n. exits the middle ear through the anterior wall

Postganglionic sympathetic nerve fibers from the internal carotid a. pass through the anterior wall to enter the middle ear

Facial canal— passes superoinferiorly immediately posterior to the middle ear until it terminates at the stylomastoid foramen

Mastoid antrum— located in the superior portion of the posterior wall near the junction with the roof of the middle ear

Pyramid— a hollow projection from the posterior wall; contains the tendon of the stapedius m.

Posterior cranial fossa and sigmoid sinus are located posterior to the posterior wall

The medial wall separates the middle ear from the inner ear

Promontory— a large protuberance created by the cochlea of the inner ear

In the superior portion of the medial wall is a protuberance formed by the lateral semicircular canal

Inferior to the lateral semicircular canal on the opposite side of the medial wall is the horizontal portion of the facial canal

Fenestra vestibuli (oval window—where the footplate of the stapes is located) and fenestra cochleae (round window—an opening covered by a membrane)—located in a superior–inferior relationship on the medial wall posterior to the promontory

Tendon of the tensor tympani m. enters the middle ear through the medial wall

The lateral wall separates the middle ear from the external ear; mainly created by the tympanic membrane, with the malleus attached to the membrane at the umbo

Epitympanic recess— the region superior to the tympanic membrane that houses portions of the malleus and incus

Chorda tympani n. lies along the tympanic membrane and malleus until exiting the petrotympanic fissure

Located in the petrous portion of the temporal bone

Surrounds the membranous labyrinth and contains perilymph

Connects to the middle ear via the fenestra vestibuli and the fenestra cochleae

Divided into 3 parts—vestibule, cochlea, and semicircular canals

The middle portion of the osseous labyrinth, it contains the saccule and utricle of the membranous labyrinth

Contains an opening for the vestibular aqueduct containing the endolymphatic duct

Anterior portion of the osseous labyrinth contains the cochlear duct of the membranous labyrinth

Like a seashell, it spirals around a central point (the modiolus), which carries branches of the cochlear n. to the cochlear duct, for 2¾ turns, getting progressively smaller as it approaches its apex

As the cochlea spirals, the spiral lamina is raised from the modiolus

Within the spiral lamina, the cochlear duct lies between the scala vestibuli and the scala tympani

Scala vestibuli and scala tympani are continuous at the helicotrema at the apex

An opening for the aqueduct of the cochlea allows perilymph to drain into the cerebrospinal fluid

The posterior portion of the osseous labyrinth

3 semicircular canals— anterior, posterior, and lateral

Ampulla— a dilated end of each

Anterior and posterior semicircular canals have a common crus

Located within the osseous labyrinth; contains endolymph

Divided into 4 parts—cochlear duct, saccule, utricle, and semicircular ducts

A spiral structure located within the cochlea

Begins at a blind end of the cochlea at the apex and ends where it joins the saccule via the ductus reuniens

Triangular in shape, with a base created by the endosteum of the canal known as the spiral ligament and the stria vascularis

Roof is formed by the vestibular membrane that separates the cochlear duct from the scala vestibuli

Floor is formed by the basilar membrane, on which lies the organ of Corti; separates the duct from the scala tympani

A small structure located within the vestibule of the osseous labyrinth

Connected to the utricle via the utriculosaccular duct and the endolymphatic duct

Sensory receptors (the maculae) are located in the saccule

Located within the vestibule of the osseous labyrinth

Sensory receptors (maculae) are located in the utricle

Correspond to the semicircular canals of the osseous labyrinth (anterior, posterior, and lateral)

Open into the utricle via 5 openings

Sensory receptors known as crista are located in the ampullae of the semicircular ducts