Skull Divisions: Neurocranium (Braincase) and Viscerocranium (Facial Skeleton)

The skull comprises 22 bones (excluding auditory ossicles) divided into two developmental and functional units:

Neurocranium (8 bones)

Forms the cranial cavity protecting the brain and sensory organs.

• Frontal (1)
• Parietal (2)
• Temporal (2)
• Occipital (1)
• Sphenoid (1)
• Ethmoid (1)

Viscerocranium (14 bones)

Forms the facial skeleton, housing orbits, nasal cavity, and oral cavity; supports respiratory/digestive entry.

• Nasal (2)
• Maxilla (2)
• Zygomatic (2)
• Palatine (2)
• Lacrimal (2)
• Vomer (1)
• Mandible (1)

Key Sutures

• Coronal (frontal-parietal), Sagittal (parietal-parietal), Lambdoid (parietal-occipital), Squamous (temporal-parietal).
• Metopic (frontal) usually fuses by 2 years; persistence = metopic suture.

Clinical Relevance

• Craniosynostosis: premature suture fusion → abnormal head shape, increased ICP.
• Facial fractures: Le Fort I/II/III patterns.
• Fontanelles: anterior (closes 12–18 mo), posterior (closes 2–3 mo).