Scalp
Calva
Definition
The scalp is the soft tissue covering of the cranial vault, extending from the supraorbital ridges anteriorly to the superior nuchal line posteriorly, and laterally to the temporal lines. It is classically described as consisting of five layers, remembered by the mnemonic SCALP:
Skin — the thickest skin in the body, containing numerous hair follicles, sebaceous glands, and a rich blood supply.
Connective tissue (subcutaneous) — a dense fibrofatty layer containing the major blood vessels and nerves of the scalp. Because the vessels are held open by the surrounding fibrous septa, lacerations in this layer tend to bleed profusely.
Aponeurosis (galea aponeurotica) — a tough, tendinous sheet connecting the frontalis muscle anteriorly to the occipitalis muscle posteriorly. This layer provides structural integrity and is the key layer for surgical closure of scalp wounds.
Loose areolar connective tissue — a potential space often referred to as the "danger zone" of the scalp, as infections or blood collections in this layer can spread easily across the calvarium and may reach the intracranial venous sinuses via emissary veins.
Pericranium (periosteum) — the outermost periosteal layer firmly adherent to the underlying skull bones, particularly at the suture lines.
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