The Cranial Cavity Lecture 7

Cranial Cavity Overview

• Contains the brain, meninges, cranial nerves, arteries, veins, and venous sinuses.

Vault of the Skull

• Features coronal, sagittal, and lambdoid sutures on the internal surface.
• Midline shows a shallow sagittal groove for the superior sagittal sinus.
• Granular pits house lateral lacunae and arachnoid granulations alongside the groove.
• Narrow grooves accommodate anterior and posterior divisions of middle meningeal vessels.

Base of the Skull

• Divided into three cranial fossae: anterior, middle, and posterior.
• Anterior cranial fossa separated from middle fossa by the lesser wing of the sphenoid.
• Middle fossa separated from posterior fossa by the petrous part of the temporal bone.

Anterior Cranial Fossa

• Houses frontal lobes of cerebral hemispheres, bounded by the frontal bone.
• Sharp lesser wing of the sphenoid forms the posterior boundary.
• Crista galli, an upward projection of the ethmoid bone, provides attachment for the falx cerebri.
• Cribriform plate has perforations for olfactory nerves, supporting olfactory bulbs.

Middle Cranial Fossa

• Comprises a median raised part and expanded lateral concavities for temporal lobes.
• The sphenoid bone resembles a bat with a body and outstretched wings.
• The body of the sphenoid houses sphenoid air sinuses, which resonate voice.
• Optic canal transmits optic nerve and ophthalmic artery.
• Superior orbital fissure conveys multiple cranial nerves and superior ophthalmic vein.
• Foramen rotundum transmits maxillary nerve; foramen ovale transmits mandibular nerve.
• Foramen spinosum transmits the middle meningeal artery; foramen lacerum is filled with cartilage.

Posterior Cranial Fossa

• Deep fossa housing the cerebellum, pons, and medulla oblongata.
• Bounded anteriorly by superior border of the petrous temporal bone, posteriorly by squamous occipital bone.
• Internal occipital crest runs from foramen magnum to internal occipital protuberance.
• Wide grooves for transverse sinuses on either side of the internal occipital protuberance.

Neonatal Skull

• Newborn skull has a larger cranium in proportion to the face.
• Growth of mandible, maxillary sinuses, and alveolar processes increases facial length during childhood.
• Skull bones are generally ossified but movable, connected by fibrous tissue or cartilage.
• Bones of the vault ossified in membrane, while base bones ossified in cartilage.
• Sutures in the vault are less tightly knit, leaving unossified membranous intervals known as fontanelles.
• Anterior fontanelle is diamond-shaped, located between frontal and parietal bones, closes by 18 months.
• Posterior fontanelle is triangular, located between parietal and occipital bones, usually closed by the end of the 1st year.
• Mandible consists of right and left halves united by fibrous tissue, fusing by the end of the 1st year.
• The angle of the mandible changes to adult shape post-eruption of permanent teeth.

Explore the intricacies of the cranial cavity in this informative lecture. Delve into its structure, including the brain, meninges, and crucial sutures. Understand the significance of the superior sagittal sinus and granular pits in skull anatomy.