Pericranium

The pericranium, or the periosteum of the skull, is a dense connective tissue membrane that covers the external surface of the cranial bones (the calvaria). It forms the innermost layer of the scalp, lying beneath the epicranial aponeurosis and the loose areolar tissue, and is firmly attached to the outer cortical bone. At the cranial sutures, the pericranium is continuous with the periosteum of adjacent bones.

Anatomy and attachments: The pericranium adheres closely to the outer tables of the skull bones and is separated from the galea aponeurotica by a layer of loose areolar tissue, the subaponeurotic space. It contains a vascular network and nerve endings and is penetrated by vessels that supply the skull. Sharpey's fibers help anchor the pericranium to the bone, stabilizing it against movement relative to the calvaria.

Function and clinical significance: The pericranium provides a source of osteogenic cells capable of contributing to bone healing, particularly in younger individuals. It is also used clinically as a vascularized pericranial flap in neurosurgical and skull-base procedures to reconstruct dura or cover skull defects. In surgical practice, the pericranium is often preserved or mobilized to maintain vascularity for healing after craniotomies or bone reconstruction, and it can be raised as a flap when needed.

In summary, the pericranium is the skull’s external periosteum, essential for bone health and repair and a valuable autologous tissue graft in cranial surgery.