Skull Anatomy Lecture

Importance of the Skull

• Protects the brain: Forms a protective barrier for the brain, sensory organs, and important structures such as arteries.
• Composition: 22 bones — 14 facial bones and 8 cranial bones.
• Cranium: Divided into two parts
  • Facial bones (viscerocranium)
  • Brain case (neurocranium)
• Mandible: The only movable bone in the skull

Bones in the Skull

• Facial Bones (Viscerocranium):

  • 6 paired bones: Nasal, Maxillary, Zygomatic, Palatine, Lacrimal, and Inferior Nasal Concha
  • 2 single bones: Vomer and Mandible

• Neurocranium:

  • Calvaria (roof of the skull)
  • Cranial base (base of the skull)
  • 4 single bones: Frontal, Occipital, Ethmoid, Sphenoid
  • 2 paired bones: Parietal and Temporal

Viscerocranium Details

• Nasal Bone: Paired, forms the bridge of the nose.
• Maxillary Bone: Paired, forms the upper jaw and holds upper teeth.
• Zygomatic Bone: Paired, forms the cheekbones.
• Palatine Bone: Paired, forms part of the hard palate.
• Lacrimal Bone: Smallest and most fragile bone in the face, located in the corner of the eye.
• Inferior Nasal Concha: Paired, located inside the nasal cavity.
• Vomer: Single, forms part of the nasal septum.
• Mandible: Single, forms the lower jaw and holds lower teeth.

Neurocranium Details

• Frontal Bone: Single, forms the forehead and part of the orbital cavity.
  • Has frontal eminences and supraciliary arches.
• Parietal Bone: Paired, forms the sides and roof of the cranial cavity.
  • Includes parietal foramen and parietal eminences.
• Temporal Bone: Paired, forms the lower sides of the skull and part of the cranial base.
  • Contains structures such as the mastoid process and zygomatic process.
• Occipital Bone: Single, forms the posterior part of the skull.
• Ethmoid Bone: Single, forms the roof of the nasal cavity.
  • Contains cribriform plate for olfactory nerves.
• Sphenoid Bone: Single, complex bone located at the base of the skull, behind the ethmoid.
  • Contains greater and lesser wings, and the sella turcica for the pituitary gland.

Sutures of the Skull

• Sagittal Suture: Between two parietal bones.
• Coronal Suture: Between frontal and parietal bones.
• Lambdoid Suture: Between parietal and occipital bones.
• Pterion: An H-shaped junction where the frontal, parietal, temporal, and sphenoid bones meet. Important due to vulnerability in trauma.

Fontanels in Newborns

• Anterior Fontanel: Closes by 18 months.
• Posterior Fontanel: Closes by 6 months.
• Importance: Allow for brain growth and easier passage through the birth canal.

Paranasal Sinuses

• Frontal, Maxillary, Ethmoid, Sphenoid Sinuses:
  • Function in reducing skull weight and enhancing voice resonance.

Clinical Points

• Middle Meningeal Artery: Located under the pterion, susceptible to injury, can cause extradural hematoma.
• Extradural Hematoma: Accumulation of blood between the dura mater and the skull, usually due to trauma.

CSF and Meninges

• Meninges: Protective layers covering the brain and spinal cord:
  • Dura Mater: Outer layer
  • Arachnoid Mater: Middle layer
  • Pia Mater: Inner layer
• Cerebrospinal Fluid (CSF): Circulates in the subarachnoid space, provides cushioning and nutrients.
  • Produced by ependymal cells, absorbed by arachnoid granulations.
• Granular Foveolae: Depressions in the skull indicating the location of arachnoid granulations.

Summary

• The skull consists of numerous bones with specific functions and relationships.
• Important sutures and fontanels facilitate growth and protection.
• Sinuses contribute to various physiological functions.
• Clinical relevance of skull anatomy includes implications for injury and surgical procedures.