Osteology of the Skull

Learning Objectives

• Understand and list the bones of the neurocranium and their features.
• Identify and list the facial bones and their features.
• Learn about the four sutures of the skull and which bones meet at these sutures.
• Describe the bony landmarks on the superior and inferior surfaces of the skull base.
• List and describe the bony landmarks of the mandible.
• Identify and describe the paranasal sinuses.
• Recognize the major foramina of the skull.

Skull Overview

• The skull is divided into two main groups:
  • Neurocranium: 8 bones that enclose the brain.
  • Viscerocranium: 14 bones that form the face.

Neurocranium Bones (8 Total)

• Frontal Bone: 1
• Parietal Bones: 2
• Temporal Bones: 2
• Occipital Bone: 1
• Ethmoid Bone: 1
• Sphenoid Bone: 1

Viscerocranium Bones (14 Total)

• Zygomatic Bones: 2
• Maxilla Bones: 2
• Palatine Bones: 2
• Lacrimal Bones: 2
• Nasal Bones: 2
• Vomer Bone: 1
• Inferior Nasal Concha Bones: 2
• Mandible: 1

Sutures of the Skull

• Sutures are immovable joints where the plates of the skull fuse.
• Four Main Sutures:
  • Coronal Suture
  • Sagittal Suture
  • Lambdoidal Suture
  • Squamosal Suture

Facial Features and Structures

• Orbit:
  • Comprised of seven bones.
  • Contains three foramina for passage of nerves and blood vessels.
• Landmarks of the Skull Base (Superior):
  • Frontal Crest: Anterior prominence.
  • Crista Galli: Attachment for dura mater.
  • Cribiform Plate: Olfactory nerves pass here.
  • Sella Turcica: Location of the pituitary gland.
  • Clivus: Slope where brainstem rests.

Bony Landmarks (Inferior)

• Medial and Lateral Pterygoid Plates
• Pterygoid Fossa
• Zygomatic Arch
• Mandibular Fossa
• Styloid and Mastoid Processes
• Occipital Condyle
• Inion

Mandible Anatomy

• Landmarks:
  • Ramus: Vertical part of the mandible.
  • Body: Horizontal part of the mandible.
  • Angle: Junction of the ramus and body.
  • Condyloid Process: Articulates with the temporal bone at the TMJ.
  • Coronoid Process: Muscle attachment site.
  • Mandibular Foramen: Passage for the inferior alveolar nerve.
  • Mental Foramen: Exit point for mental nerve.

Paranasal Sinuses

• Function: Air-filled spaces lined with mucous membranes, reducing skull weight.
• Present in four bones:
  • Frontal Bone
  • Ethmoid Bone
  • Sphenoid Bone
  • Maxillary Bone

Features of Ethmoid Bone

• Orbital Plate: Forms part of the eye socket.
• Crista Galli: Point of attachment for dura mater.
• Perpendicular Plate: Contributes to nasal septum.

Features of Sphenoid Bone

• Optic Canal: Route for optic nerve.
• Foramen Ovale: For passage of V3 branch of trigeminal nerve.
• Pterygoid Canal: Connects pterygopalatine fossa to the middle cranial fossa.

References

• Grant’s Atlas of Anatomy, 8th edition
• Grant’s Dissector, 16th edition
• Gray’s Anatomy: The Anatomical Basis of Clinical Practice
• Hollinshead’s Textbook of Anatomy, 5th edition
• Moore’s Clinically Oriented Anatomy, 7th edition
• Netter’s Atlas of Human Anatomy, 5th edition