Anterior Skull USMLE, Limited Edition > Gross Anatomy > Gross Anatomy

Key functions of the skull:

• Protects the brain and associated sensory organs.

• Provides attachment sites for the facial and neck muscles.

The skull itself comprises:

• 8 Cranial bones that enclose the brain

• 14 Facial bones that protect entryway to nasal and oral cavities, and provide muscle attachment sites.

The cranial bones include:

The unpaired bones: Frontal

• Forms the forehead and superior rim of eye orbits.

• Supraorbital margin is the bony ridge framing the orbit superiorly

• Supraorbital notch/foramen provides passageway for neurovascular structures.

Occipital

• Contributes to the posterior and inferior surface and base of the skull.

Sphenoid

• A bat-shaped bone that spans the width of the skull.

Ethmoid

• An irregularly shaped bone that lies deep within the skull.

• Contributes superior and middle nasal conchae.

The paired bones: Parietal

• Comprise the superior and lateral aspects of the skull.

Temporal

• Comprise the inferior portion of the lateral skull.

The facial bones include:

1 / 3 The unpaired bones: Vomer

• Contributes to the nasal septum.

Mandible

• The bone of the lower jaw.

• Alveolar margin houses lower teeth.

• Mental foramen for neurovascular structures.

The paired: Zygomatic

• Form the inferior margins of the orbits and the lateral cheekbones.

Lacrimal

• Contribute to the medial walls of the orbits.

Nasal

• Comprise the bridge of the nose.

Inferior nasal conchae

• Lie within the nasal cavity.

Palatine

• Contribute a small portion to the medial orbit wall (but chiefly contribute to the hard palate of the oral cavity).

Maxilla

• Fuse at the midline of the face to form the medial and inferior orbit walls, cheeks, and upper jaw.

• Infraorbital foramen for neurovascular structures.

• Alveolar margin is the border of the maxilla where the upper teeth are housed.

Spaces within the eye orbit:

• The superior orbital fissure is a wide space within the sphenoid (specifically, between the greater and lesser wings).

• The inferior orbital fissure is the space between the sphenoid, zygomatic, and maxillary bones.

• The optic foramen is the opening to the optic canal, through which the optic nerve (cranial nerve II) passes.

Features of the nasal cavity:

• Nasal septum separates the nasal cavity into right and left sides.

- Comprises two different bones:

2 / 3 Superiorly: Perpendicular plate of the ethmoid bone. Inferiorly: The vomer bone comprises the inferior portion.