The Skull: Structure and Function

Overview of Skull Topography

The human skull is a complex structure composed of 8 cranial bones and 14 facial bones. It serves to protect the brain, support sensory organs, and provide attachment points for muscles. Understanding the anatomy of the skull is essential for students of anatomy and physiology.

• Cranial bones: Form the cranial cavity, encasing and protecting the brain.

• Facial bones: Shape the face and provide openings for air and food passage.

Cranium Function

• Protection: Encloses and protects the brain.

• Attachment: Provides sites for head and neck muscles.

• Bone type: Flat bones.

• Sutures: Immovable joints connecting cranial bones. Major sutures include:

  • Coronal suture: Between frontal and parietal bones.

  • Sagittal suture: Between parietal bones.

  • Lambdoid suture: Between parietal and occipital bones.

  • Squamous suture: Between parietal and temporal bones.

Facial Bones Function

• Framework: Forms the shape of the face.

• Muscle attachment: Provides sites for muscles of facial expression.

• Cavities: Houses organs of sight, taste, and smell.

• Openings: Provides passage for air and food.

• Support: Secures the teeth.

Major Bones of the Skull

Cranial Bones

• Frontal bone: Forms the forehead and superior part of the orbits.

• Parietal bones: Form the superior and lateral aspects of the skull.

• Temporal bones: Form the lateral aspects and base of the skull; contain structures for hearing.

• Occipital bone: Forms the posterior part and base of the skull.

• Sphenoid bone: Spans the width of the cranial floor; contains the sella turcica.

• Ethmoid bone: Forms part of the nasal cavity and orbits.

Facial Bones

• Mandible: Lower jawbone; only movable bone of the skull.

• Maxilla: Upper jawbone; forms part of the orbits and nasal cavity.

• Zygomatic bones: Cheekbones; articulate with maxilla and temporal bones.

• Nasal bones: Form the bridge of the nose.

• Lacrimal bones: Form part of the medial wall of each orbit.

• Palatine bones: Form part of the hard palate.

• Vomer: Forms part of the nasal septum.

• Inferior nasal conchae: Form part of lateral walls of nasal cavity.

Key Sutures of the Skull

• Coronal suture: Frontal and parietal bones.

• Sagittal suture: Parietal bones.

• Lambdoid suture: Parietal and occipital bones.

• Squamous suture: Parietal and temporal bones.

Bony Boundaries of Skull Cavities

Orbits

The orbits are bony cavities that house the eyes and associated structures.

• Formed by the frontal, sphenoid, ethmoid, lacrimal, maxilla, zygomatic, and palatine bones.

Nasal Cavity

The nasal cavity is formed by several bones and is divided by the nasal septum.

• Bounded by the ethmoid, vomer, maxilla, palatine, and inferior nasal conchae.

Paranasal Sinuses

Sinuses are air-filled cavities that lighten the skull and enhance voice resonance.

• Frontal sinus

• Maxillary sinus

• Ethmoid sinus

• Sphenoid sinus

Small Cavities in the Skull

• Orbits: House the eyes.

• Nasal cavity: Passage for air; contains olfactory receptors.

• Sinuses: Air-filled spaces that lighten the skull and provide resonance for voice.

Major Foramina and Markings

Foramina

• Foramen magnum: Large opening in occipital bone for spinal cord.

• Optic canal: Passage for optic nerve (CN II).

• Internal acoustic meatus: Passage for nerves and vessels in temporal bone.

• Jugular foramen: Passage for jugular vein and cranial nerves IX, X, XI.

• Carotid canal: Passage for carotid artery.

Other Markings

• External occipital protuberance: Prominent projection on occipital bone.

• Mastoid process: Attachment for neck muscles.

• Sella turcica: Depression in sphenoid bone housing the pituitary gland.

Classification Table: Cranial vs. Facial Bones

Summary of Key Terms

• Suture: Immovable joint between skull bones.

• Foramen: Opening in bone for nerves and blood vessels.

• Process: Projection from a bone for muscle attachment.

• Sinus: Air-filled cavity within a bone.

Example Application

Damage to the foramen magnum can affect the spinal cord and brainstem, leading to severe neurological deficits. Fractures of the zygomatic bone may impact facial symmetry and function.

Additional info: The study notes have expanded on the brief points in the images to provide a comprehensive overview suitable for exam preparation in Anatomy & Physiology.