Axial 3/5 - Skull Structures Overview

Overview

This lecture covers additional skeletal structures of the skull, including the bones of the orbit, sutures, fontanelles, sinuses, cranial fossae, and the unique hyoid bone.

Bones of the Orbit (Eye Socket)

• The orbit is formed by seven bones: frontal, sphenoid, zygomatic, maxillary, palatine, lacrimal, and ethmoid.
• The palatine bone, usually associated with the hard palate, also makes a small contribution to the orbit.
• Using a mnemonic can help remember the seven orbital bones.

Cranial Sutures

• Sutures are joints between cranial bones; examples include the coronal, squamous, lambdoid, and sagittal sutures.
• The coronal suture runs like a crown across the top of the skull.
• The squamous suture is next to the thin, flat part of the temporal bone.
• The lambdoid suture is at the back and shaped roughly like the Greek letter lambda.
• The sagittal suture separates the two parietal bones along the midline.

Fontanelles

• Fontanelles are soft spots in the fetal skull that ossify by 12–18 months of age.
• The anterior fontanelle is the largest and most clinically examined.
• Other fontanelles include the posterior, sphenoidal, and mastoid fontanelles.
• Fontanelles aid in birth and brain growth and are checked for signs of dehydration or intracranial pressure.

Paranasal Sinuses

• The four sinuses are frontal, ethmoidal, sphenoidal, and maxillary.
• Sinuses can be observed in anatomical diagrams and models of the skull.

Cranial Fossae

• The skull base contains anterior, middle, and posterior cranial fossae which house different parts of the brain.

The Hyoid Bone

• The hyoid bone is the only bone in the skeleton that does not articulate with any other bone.
• It is located between the mandible and larynx, and can be palpated in the neck.

Key Terms & Definitions

• Orbit — the bony eye socket formed by seven bones.
• Suture — an immovable joint between skull bones.
• Fontanelle — a soft, unossified area on a fetal skull.
• Sinus — an air-filled cavity within skull bones.
• Cranial fossa — a depression in the floor of the cranial cavity.
• Hyoid bone — a U-shaped bone in the neck, not attached to other bones.

Action Items / Next Steps

• Create or find a mnemonic for the seven bones of the orbit.
• Review diagrams or models to locate sutures, fontanelles, sinuses, cranial fossae, and the hyoid bone.