Hearing Science: Exploring the Temporal Bone and Its Anatomy

What does the stapes do?

vibrates the fluid inside the oval window of the inner ear

How many major bones are in the human skull?

22

How much does the adult head weigh?

8-12 pounds

How much does the skull itself weigh?

2.2 pounds

How big is the human skull

8" x 8" x 8"

What is the temporal bone?

forms the side and base of the skull

What are the four major articulations within the temporal bone?

Occipital bone

Parietal bone

Sphenoid bone

Zygomatic bone

Central

related to the brain

Peripheral

related to structure which is distal to the brain

Occipital Bone

posterior to the temporal bone

-skullbase

Parietal Bone

superior and posterior to the temporal bone

Sphenoid Bone

anterior and medial to the temporal bone

Zygomatic Bone

anterior to the temporal bone

What are the four major divisions of the temporal bone?

Squamas

Mastoid

Tympanic

Petrous

How is the squamos characterized?

cover with or characterized by scales

-consisting of or denoting a layer of epithelium that consists of very thin flattened cells

What does the squamas protect?

it protects the skull contents (in the event of a significant blow to the head, the temporal bone will shatter, absorbing much of the energy before it reaches the middle and inner ears)

Squamas Portion

-located on the lateral surface of the skull

-thin plate of hard bone

-exterior surface roughened for muscle attachments

Mastoid Portion

-located posteriorly and inferiorly to the external ear canal

-forms part of the skull base

-contains air cells that are lined with mucus membrane

-exterior surface: muscle attachment

-protective function for skull contents

How is the mastoid shaped?

like a nipple

Which portion of the temporal bone contains air cells?

mastoid portion

-it is the extension of the airway from the nasopharynx, eustachian tube, middle ear

Tympanic Portion

-related to the middle ear or ear drum

-cartilaginous portion of ear canal is the outer 1/3; the bony portion is the inner 2/3

-provides rigid superstructure to canal (keeps canal open)

What does the tympanic portion form?

the anterior, inferior, and part of the posterior walls of the external ear canal

Where is the middle ear located?

tympanic cavity

Petrous Portion

relating to or resembling a rock. especially in hardness (stony)

-located between the middle fossa and posterior fossa on the cranium floor

-located in the interior of the cranium floor

-triangular shaped (petrous pyramid); the base is wider than the apex

-contains the inner ear

What does the petrous portion separate?

the posterior fossa and middle fossa

-anterior surface faces the middle fossa

-posterior surface faces the posterior fossa

What does the petrous portion protect?

the cochlea

Fossa

a small cavity or depression

What two structures are within the petrous portion?

Tympanum (tympanic cavity for the middle ear)

Bony labyrinth (chamber for the inner ear)

Where is the tympanic membrane located?

within the tympanic cavity of the middle ear

What is a part of the anterior surface of the petrous bone?

tegman tympani and arcuate eminence

Tegman Tympani

roof of the middle ear (roof of tympanic cavity)

-thin, smooth area

Arcuate Eminence

prominence on the anterior surface of the petrous portion of the temporal bone

-superior semicircular canal is below,

along with rest of inner ear

-slight bulge

What is a feature of the posterior surface of the petrous portion of the temporal bone?

internal auditory canal

Internal Auditory Canal

contains the internal ear canal and VIIIth nerve (hearing nerve)

What are the four structures within the internal auditory canal?

Cochlear branch of the VIIIth nerve

Vestibular branch of the VIIIth nerve

Facial nerve (VIIth nerve)

Blood supply: artery