TEMPORAL BONE ANATOMY

GENERAL CHARACTERISTICS

What is the temporal bone?

• Complex cranial bone situated on your skull's lateral and basal aspects
• Located adjacent to your external ears
• Supports your temporal region
• Contains structures for your hearing and balance
• Protects your inner ear organs
• Articulates with surrounding cranial bones

STRUCTURAL COMPONENTS

What are the parts of the temporal bone?

• Irregular bone composed of multiple distinct parts:
  • Squamous part
  • Tympanic part
  • Petromastoid part
    • Petrous portion
    • Mastoid portion

PETROUS PART

General Features

What is the petrous part of the temporal bone?

• Pyramid-shaped region
• Contains apex and base
• Three surfaces present
• Three borders present
• Base oriented laterally
• Among the densest bones in your body
• Houses your inner ear structures

Apex Region

What does the petrous apex articulate with?

• Articulates with greater wing of sphenoid
• Articulates with basilar portion of occipital bone

Posterior Border and Mastoid Features

What is the posterior border of the petrous part?

• Posterior Border (occipital margin) — articulates with occipital bone

What is the mastoid process?

• Mastoid Process — prominent bony projection
  • Located on external surface of posterior region
  • Serves as attachment for your cervical muscles

What is the mastoid notch?

• Mastoid Notch — groove inferior to mastoid process
  • Attachment site for digastric muscle posterior belly

What is the occipital artery groove?

• Occipital Artery Groove — posterior to mastoid notch
  • Accommodates occipital artery during cranial ascent

What is the mastoid foramen?

• Mastoid Foramen — posterior to mastoid process
  • Transmits emissary veins
  • Connects sigmoid sinus to posterior scalp

Inferior Surface and Carotid Canal

What is the carotid canal?

• Carotid Canal — significant passageway in petrous region
  • Begins on inferior petrous surface
  • Opens at petrous apex
  • External opening located medial to jugular fossa
  • Internal opening situated at petrous apex
  • Transmits internal carotid artery to your cranial cavity
  • Supplies your cerebral blood flow

Musculotubal Canal

What is the musculotubal canal?

• Divided by thin bony septum into two semicanals
• Upper Semicanal — transmits tensor tympani muscle
• Lower Semicanal — accommodates your auditory tube
  • Also termed Eustachian tube
  • Connects your middle ear to your nasopharynx
  • Equalizes pressure across your tympanic membrane
• Opens into tympanic cavity
• Located anterior to carotid canal external opening

TYMPANIC PART

General Features

What is the tympanic part of the temporal bone?

• Curved bony plate
• Positioned anterior to mastoid process
• Forms anterior wall of your external acoustic meatus
• Forms floor of your external acoustic meatus
• Forms partial posterior wall of your external acoustic meatus

Developmental Aspects

How does the tympanic part develop?

• Exists as tympanic ring in neonates
• Fuses with squamous part after birth
• Expands to form the mature tympanic part

External Acoustic Meatus

What is the external acoustic meatus?

• Bony External Acoustic Opening — meatus entrance
• External Acoustic Meatus — oval canal
  • Approximately 1 cm in length
  • Formed by tympanic and squamous parts

What is the tympanic sulcus?

• Tympanic Sulcus — groove within tympanic ring
  • Attachment site for your tympanic membrane circumference

What is the tympanic notch?

• Tympanic Notch — superior deficiency in tympanic ring
  • Allows chorda tympani nerve passage

Tympanic Spines and Styloid Process

What are the tympanic spines?

• Tympanic Spines:
  • Greater Tympanic Spine — anterior ring projection
  • Lesser Tympanic Spine — posterior ring projection

What is the styloid process?

• Styloid Process Sheath
  • Extends posteriorly from carotid canal
  • Encircles styloid process
• Styloid Process — slender bony projection
  • Attachment for your lingual muscles
  • Attachment for your pharyngeal ligaments

SQUAMOUS PART

General Features

What is the squamous part of the temporal bone?

• Thin flat portion
• Located anterosuperiorly
• Contributes to your temporal fossa

Surfaces

What is the temporal surface of the squamous part?

• Temporal Surface — outer aspect
  • Smooth and convex
  • Provides your temporalis muscle attachment

What is the cerebral surface of the squamous part?

• Cerebral Surface — inner aspect
  • Concave configuration
  • Accommodates your temporal lobe of cerebrum
  • Contains grooves for middle meningeal vessels
  • Shows impressions from cerebral gyri

Borders and Margins

What are the borders of the squamous part?

• Superior Border (parietal border)
  • Articulates with parietal bone
  • Forms part of squamous suture
• Parietal Notch — angle between parietal border and mastoid superior border
• Sphenoidal Margin — anteroinferior location
  • Articulates with greater sphenoid wing

Zygomatic Process and Related Structures

What is the zygomatic process of the temporal bone?

• Zygomatic Process — arched projection
  • Extends from inferior squamous portion
  • Contributes to your zygomatic arch
  • Connects with temporal process of zygomatic bone

What is the supramastoid crest?

• Supramastoid Crest — continues posteriorly from zygomatic process root

What is the suprameatal fovea?

• Suprameatal Fovea — small depression
  • Located between external acoustic meatus posterior wall
  • Located between zygomatic process posterior root
• Suprameatal Spine — anatomical landmark near your external acoustic meatus

Mandibular Fossa

What is the mandibular fossa?

• Mandibular Fossa — concave depression
  • Located on inferior squamous surface
  • Contributes to your temporomandibular joint
  • Articulates with mandibular condyle

What is the articular tubercle?

• Articular Surface — anterior mandibular fossa portion
  • Contacts your mandible directly
• Articular Tubercle — rounded eminence anterior to fossa
  • Prevents excessive posterior mandibular displacement when you open your jaw

TEMPORAL BONE FISSURES

What are the temporal bone fissures?

• Separate different bone parts
• Allow nerve and vessel passage

What is the petrotympanic fissure?

• Petrotympanic Fissure
  • Located between mandibular fossa and tympanic part
  • Posterior to petrosquamous fissure

What is the petrosquamous fissure?

• Petrosquamous Fissure
  • Anterior to petrotympanic fissure
  • Separates petrous from squamous parts

What is the tympanosquamous fissure?

• Tympanosquamous Fissure
  • Continues petrosquamous and petrotympanic fissures laterally
  • Located between tympanic and squamous parts

What is the tympanomastoid fissure?

• Tympanomastoid Fissure
  • Formed by posterior tympanic edge and mastoid part