Overview
This lecture reviews the bones and key features seen inside the skull, focusing on identifying various cranial bones, sutures, and major foramina.
Cranial Bones and Sutures
- The frontal bone forms the front of the skull.
- The ethmoid bone is located between the frontal bones and contains the cribriform plate.
- The sphenoid bone sits centrally and appears in several regions inside the skull.
- The temporal bones are located on the sides and lower part of the skull.
- The occipital bone is found at the back of the skull.
- Key sutures separate these bones, marking their borders.
Important Features of the Ethmoid and Sphenoid Bones
- The cribriform plate is a perforated area of the ethmoid bone for olfactory nerves.
- The lesser wings are projections on the sphenoid bone.
- The greater wings (noted as "brain wings") extend laterally from the sphenoid.
- The sella turcica on the sphenoid bone houses the pituitary gland.
Major Cranial Foramina (Openings)
- The foramen magnum is a large hole in the occipital bone for the spinal cord.
- Foramen ovale, foramen spinosum, and foramen rotundum are holes in the sphenoid bone.
- The foramen lacerum is found near the sphenoid and temporal bones.
- The carotid canal passes through the temporal bone, allowing passage of the carotid artery.
- The jugular foramen is a large opening near the occipital and temporal bones for veins and nerves.
- Internal acoustic meatuses are small holes in the temporal bone for cranial nerves.
Key Terms & Definitions
- Frontal bone — the bone forming the forehead.
- Ethmoid bone — a bone at the base of the skull, between the eyes.
- Cribriform plate — a perforated part of the ethmoid bone for olfactory nerve fibers.
- Sphenoid bone — a central skull bone with lesser and greater wings.
- Lesser wings — thin projections of the sphenoid bone.
- Sella turcica — a depression in the sphenoid that holds the pituitary gland.
- Foramen magnum — the large opening in the occipital bone for the spinal cord.
- Foramen ovale/spinosum/rotundum — smaller openings in the sphenoid bone for nerves and blood vessels.
- Carotid canal — passage in the temporal bone for the carotid artery.
- Jugular foramen — opening for jugular vein and cranial nerves.
- Internal acoustic meatus — a canal in the temporal bone for auditory nerves.
Action Items / Next Steps
- Review diagrams of the internal skull to identify each bone and foramen discussed.
- Memorize the locations and functions of the key foramina.