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