Learning Objective: Describe the anatomy of the skull, including the bones of the cranium and face, their sutures, and key clinical correlations such as fractures and fontanelles.
The skull is a bony structure that supports the face and forms a protective cavity for the brain. It is formed by intramembranous ossification and joined by fibrous sutures.
It can be divided into two parts:
- Cranium (neurocranium) – protects the brain.
- Facial skeleton (viscerocranium) – forms the framework of the face.
Cranium
The cranium encloses and protects the brain, meninges, and cerebral vasculature.
Subdivisions:
- Cranial roof (calvaria): Frontal, occipital, and parietal bones.
- Cranial base: Frontal, sphenoid, ethmoid, occipital, parietal, and temporal bones.
These articulate with the atlas (C1), facial bones, and mandible.
Clinical Relevance: Cranial Fractures
Fractures may result from blunt or penetrating trauma.
A key region is the pterion, the H-shaped junction of the temporal, parietal, frontal, and sphenoid bones.
- The middle meningeal artery lies deep to the pterion.
- A fracture here can rupture this vessel, causing an epidural hematoma — a neurosurgical emergency.
Facial Skeleton
The viscerocranium supports the facial soft tissues and forms the orbits, nasal, and oral cavities.
Facial bones (14 total):
- Zygomatic (2) – cheekbones.
- Lacrimal (2) – the smallest facial bones; the medial orbital wall.
- Nasal (2) – bridge of the nose.
- Inferior nasal conchae (2) – increase nasal surface area.
- Palatine (2) – posterior part of the hard palate.
- Maxilla (2) – upper jaw and anterior hard palate.
- Vomer (1) – posterior nasal septum.
- Mandible (1) – lower jaw; articulates at TMJ.
Clinical Relevance: Facial Fractures
Common causes: trauma, falls, road traffic accidents.
Types:
- Nasal fracture – most common; causes swelling, deformity, and epistaxis.
- Maxillary fracture (Le Fort I–III) – high-energy trauma.
- Mandibular fracture – often bilateral with malocclusion.
- Zygomatic arch fracture – may injure the infraorbital nerve → cheek/nose/lip paresthesia.
Sutures of the Skull
Sutures are immovable fibrous joints that fuse by age 20.
Main sutures:
- Coronal – frontal ↔ parietal bones.
- Sagittal – between parietal bones.
- Lambdoid – occipital ↔ parietal bones.
In neonates:
- Frontal fontanelle: junction of coronal + sagittal sutures.
- Occipital fontanelle: junction of sagittal + lambdoid sutures.
These fontanelles allow skull deformation during birth and accommodate brain growth.
