FRONTAL BONE ANATOMY

GENERAL CHARACTERISTICS

• Major cranial bone forming the forehead
• Contributes to orbital roofs
• Contributes to anterior cranial floor
• Articulations:
  • Sphenoid bone
  • Ethmoid bone
  • Paired parietal bones
  • Paired nasal bones
  • Paired maxillae
  • Paired lacrimal bones
  • Paired zygomatic bones

SQUAMOUS PART

• Vertical flattened region forming the forehead
• External aspect is smooth and convex
• Faces outward toward the scalp

Frontal Eminences

• Paired rounded prominences
• Located approximately 3 cm above supraorbital margin
• Positioned on either side of midline
• Contribute to forehead contour

Superciliary Arches

• Paired elevations
• Located directly above supraorbital margin
• Accentuate brow prominence

Glabella

• Smooth midline elevation
• Situated between superciliary arches

Frontal Portion of Orbital Margin

• Forms inferior boundary of squamous part

External Surface Features

• Smooth convex surface
• Forms visible forehead area
• Supraorbital Notch or Foramen:
  • Located on medial aspect of supraorbital margin
  • Transmits neurovascular structures
• Frontal Notch or Foramen:
  • Positioned medial to supraorbital notch
  • Provides passage for vessels and nerves
  • Supplies the forehead region

TEMPORAL SURFACE

• Lateral aspect of frontal bone
• Contributes to temple region
• Parietal Margin — posterior border
  • Articulates with parietal bones
• Zygomatic Process — prominent lateral projection
  • Located at lateral end of supraorbital margin
  • Articulates with zygomatic bone
  • Forms part of lateral orbital wall
  • Forms part of orbital rim
• Temporal Line:
  • Extends superiorly from zygomatic process
  • Extends posteriorly from zygomatic process
  • Divides into superior and inferior temporal lines
  • Attachment for temporalis muscle
  • Attachment for temporal fascia

INTERNAL SURFACE OF SQUAMOUS PART

• Faces the cranial cavity
• Frontal Crest — midline ridge
  • Formed by convergence of sagittal sulcus margins
  • Located at inferior midline
• Foramen Cecum:
  • Located at inferior end of frontal crest
  • Formed by small notch uniting with ethmoid bone
  • Transmits small veins
  • Connects nasal cavity to superior sagittal sinus

NASAL PART

• Inferior extension of frontal bone
• Positioned between supraorbital margins
• Nasal Spine — midline bony projection
  • Extends inferiorly from center of nasal part
  • Articulates with nasal bones
  • Articulates with perpendicular plate of ethmoid
• Nasal Margin — inferior border
  • Articulates with superior borders of nasal bones
  • Contributes to nasal bridge formation

ORBITAL PART

• Composed of two horizontal triangular plates called orbital plates
• Forms orbital roofs
• Forms anterior cranial fossa floor
• Ethmoidal Notch — gap between orbital plates
  • Accommodates cribriform plate of ethmoid bone
• Orbital Surface:
  • Inferior-facing aspect of each orbital plate
  • Directed into the orbit

Key Features of Orbital Surface

• Trochlear Fovea — small medial depression
  • Located near nasal part
  • Attachment site for trochlea
  • Serves superior oblique muscle
• Fossa for Lacrimal Gland — shallow depression
  • Located laterally
  • Houses the lacrimal gland
• Sphenoidal Margin:
  • Articulates with greater wing of sphenoid bone
  • Completes anterior cranial fossa

FRONTAL SINUSES

• Paired irregular cavities
• Located within frontal bone
• Positioned superior to orbits
• Positioned posterior to superciliary arches
• Septum of Frontal Sinuses — thin bony partition
  • Separates the two cavities
  • Variable position
  • Often results in asymmetrical sinuses
• Drainage Openings:
  • Open into nasal cavity
  • Located on either side of nasal spine
  • Positioned anterior to ethmoidal notch
• Functions:
  • Humidification of inspired air
  • Voice resonance enhancement
  • Reduction of skull weight