What is the calvaria and what bones form it?

The calvaria, also known as the skull cap, is the roof of the cranial cavity. It is formed by the superior parts of the frontal, parietal, and occipital bones, protecting the brain and serving as the upper boundary of the cranial fossae.

What are the key anatomical features on the internal surface of the calvaria?

The internal surface is concave and features several structures: Sagittal sulcus (midline groove for the superior sagittal sinus), granular pits (depressions for arachnoid granulations), vascular grooves (impressions from middle meningeal vessels), parietal foramina (small openings near the sagittal suture), and impressions for cerebral gyri with visible sutures (coronal, sagittal, lambdoid).

What is the layered structure of calvarial bones?

Calvarial bones have a three-layer sandwich structure: Outer table (thick, strong compact bone), diploë (spongy bone layer with red bone marrow), and inner table (thin, fragile compact bone, more prone to fracture). In children, these bones consist of a single compact bone layer.

What are diploic veins and what is their function?

Diploic veins are valveless veins that drain blood from the diploë (spongy bone layer) to the dural venous sinuses. They communicate with scalp veins and include specific veins like the frontal, anterior temporal, posterior temporal, and occipital diploic veins.

Why is the inner table of the calvaria clinically significant?

The inner table is the thin and fragile compact bone layer. Its fragility makes it more prone to fracture, which can potentially injure underlying dural vessels, leading to complications like epidural hematomas.

What are the main diploic veins and where do they drain?

Recognizable diploic veins include: Frontal diploic vein (drains via supraorbital foramen to supraorbital vein), anterior temporal diploic vein (passes to sphenoparietal sinus or anterior deep temporal vein), posterior temporal diploic vein (drains into transverse sinus), and occipital diploic vein (largest, drains into transverse sinus or occipital emissary vein).

How does the calvaria differ in children compared to adults?

In children, the calvarial bones are composed of a single compact bone layer, unlike the three-layer structure (outer table, diploë, inner table) found in adults. This developmental difference affects bone strength and fracture patterns.

Skull Cap (Calvaria) – Layers & Vascular Grooves

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