Overview
This lecture covers the anatomy of the skull, including the identification of external and internal bones, major openings (foramina), significant anatomical features, and their neurological/vascular associations.
Skull Views and Major External Bones
- Skull can be viewed from frontal (anterior), lateral (side), and superior (top-down/inside) perspectives.
- Nasal bone is located at the bridge of the nose and visible in both frontal and lateral views.
- Frontal bone forms the forehead, best seen from the frontal view.
- Maxilla is the upper jaw area, above the upper lip and surrounds the nose.
- Mandible is the lower jawbone, distinct from the maxilla.
- Zygomatic bones are the “cheekbones,” present on both sides.
- Temporal bone is at the temple region, thin and easily fractured.
- Sphenoid bone is visible inside and slightly outside the skull.
- Parietal bone is visible in the lateral view, forming the upper side of the skull.
- Occipital bone is at the back and base of the cranium.
Internal Skull Features and Foramina
- The superior view of the skull reveals three fossae: anterior, middle, and posterior (occipital) fissures.
- Crista galli is a midline bone projection in the anterior fossa.
- Petrous ridge is a noticeable ridge in the skull base.
- Foramina (holes) allow cranial nerves and blood vessels to pass through the skull.
- ROS (rotundum, ovale, spinosum)
Key Foramina and Cranial Nerve Associations
- Cribriform plate: Cranial Nerve I (olfactory) passes through.
- Optic canal/foramen: Cranial Nerve II (optic) passes through.
- Superior orbital fissure: Cranial Nerves III, IV, V1 (first branch), VI.
- Foramen rotundum: Cranial Nerve V2 (second branch).
- Foramen ovale: Cranial Nerve V3 (third branch).
- Foramen spinosum: Middle meningeal artery.
- Internal auditory meatus: Cranial Nerves VII, VIII.
- Jugular foramen: Internal jugular vein, Cranial Nerves IX, X, XI.
- Hypoglossal canal: Cranial Nerve XII (hypoglossal).
- Foramen magnum: Brainstem and spinal cord pass through.
- Stylomastoid foramen: Cranial Nerve VII.
Other Internal and External Skull Structures
- Ethmoid bone contains the cribriform plate.
- Lacrimal bone is at the inner corner of each eye.
- Sphenoid bone includes the sella turcica, which holds the pituitary gland.
- External auditory meatus is the ear canal.
- Mastoid process and styloid process project from the temporal bone.
- Inion or external occipital protuberance is a bump on the back of the skull.
- Orbits (eye sockets) contain the optic canal, superior and inferior orbital fissures.
Nasal Cavity and Sphenoid Bone Details
- Nasal septum’s key structure is the vomer.
- Turbinates (conchae) are inside the nose: superior, middle, and inferior, and help warm air.
- Sphenoid bone has greater wings, and right/left lateral and medial pterygoid processes.
Inferior Skull View
- On the bottom of the skull, the foramen magnum and occipital condyles (articulate with the spine) are visible.
Key Terms & Definitions
- Fossa — A hollow or depressed area in a bone.
- Foramen — An opening or hole in bone for nerves/blood vessels.
- Process — A projection or outgrowth on a bone.
- Condyle — A rounded protrusion at the end of a bone for articulation.
- Turbinates (Conchae) — Curved bones inside the nasal cavity to warm/clean air.
- Sella turcica — Saddle-shaped depression in the sphenoid bone for the pituitary gland.
- Crista galli — Vertical projection in the anterior cranial fossa of the ethmoid bone.
Action Items / Next Steps
- Review labeled diagrams/models of the skull in your textbook.
- Practice identifying major bones and foramina and their nerve/artery associations.
- Prepare for upcoming neurology content by memorizing cranial nerve passageways.