Lecture Notes: Structures of the Cranial Base

Overview

• The cranial base is where the brain rests.
• Discussion includes frontal bone, ethmoid bone, sphenoid bone, temporal bones, and occipital bone.

Frontal Bone

• Frontal Sinuses
  • Located in the frontal bone.
  • Air-filled cavities, not visible in non-real skulls.
  • Lined by ciliated pseudostratified columnar epithelium with goblet cells.
  • Drains mucus into nasal cavities via frontal duct.

Ethmoid Bone

• Cribriform Plate
  • Forms the roof of nasal cavities.
  • Contains olfactory foramina for olfactory fibers (cranial nerve I).
  • Thin and weak, prone to fracture.
  • Fracture can lead to cerebrospinal fluid leakage, increasing infection risk (meningitis).
• Crista Galli
  • Attachment for falx cerebri, part of dura mater.

Sphenoid Bone

• A complex, butterfly-shaped bone.
• Sections
  • Body, lesser wings, and greater wings.
• Sella Turcica
  • Includes dorsum sellae, hypophyseal fossa, tuberculum sellae.
  • Houses the pituitary gland.
• Optic Canals
  • Passage for optic nerves (cranial nerve II).
  • Proximity to pituitary gland can affect vision.
• Superior Orbital Fissure
  • Passage for several cranial nerves: oculomotor, abducens, trochlear, and ophthalmic (branch of trigeminal).
• Foramina in Greater Wings
  • Rotundum: Maxillary branch of the trigeminal nerve.
  • Ovale: Mandibular branch of the trigeminal nerve.
  • Spinosum: Part of the greater wings.
• Foramen Lacerum
  • Sits medial to ovale and spinosum, covered by fibrocartilage in living humans.

Temporal Bones

• Petrous Portion
  • Houses inner and middle ear.
  • Contains internal acoustic meatus.
  • Passage for facial and vestibulocochlear nerves.
• Jugular Foramen
  • Passage for jugular vein and cranial nerves IX, X, XI.
• Temporal Squamous
  • Flat section of the temporal bone.

Occipital Bone

• Foramen Magnum
  • Connection between medulla oblongata and spinal cord.
  • Critical for protection due to visceral control centers.
• Hypoglossal Canals
  • Passage for hypoglossal nerves (tongue movement).
• Internal Occipital Protuberance
  • Noted structure within the occipital bone.
• Parietal Bones
  • Seen in the cranial base but not discussed in detail.

Important Notes

• The lecture uses a model skull; some structures may not be visible.
• Neurovascular structures often have complex paths, entering and exiting through different openings.

Conclusion

• The lecture provided an overview of important cranial base structures and their functions.
• Emphasized the clinical relevance of fractures and anatomical pathways.