Scalp Anatomy: Five Layers and Their Functions

The Scalp: More Than Skin Deep

The scalp is a specialized five-layered structure (remembered by the mnemonic SCALP) that protects the skull, anchors hair, and supplies the brain.

S — Skin

Thicker than facial skin; dense with hair follicles (~100,000), sebaceous glands (sebum for lubrication), and eccrine sweat glands (thermoregulation). High vascularity supports rapid wound healing.

C — Connective Tissue (Subcutaneous)

Fibrofatty layer housing the main neurovascular bundles (supratrochlear, supraorbital, superficial temporal, posterior auricular, occipital arteries). Provides cushioning and allows skin mobility over deeper layers.

A — Aponeurosis (Galea Aponeurotica)

Tough, inelastic tendinous sheet connecting the frontalis and occipitalis muscles. Transmits muscular forces; a key surgical plane—lacerations here gape and require repair to prevent epicranial detachment.

L — Loose Areolar Tissue

Avascular, sponge-like layer enabling the scalp to glide over the pericranium. Also a potential space for fluid spread (hematoma, infection) from the face or sinuses—hence "danger zone" in surgery.

P — Pericranium (Periosteum)

Dense fibrous membrane adherent to the outer skull table. Provides periosteal blood supply to calvarial bone; elevated in neurosurgical approaches.

Clinical Relevance

• Vascularity: Profuse bleeding from scalp lacerations; also rapid healing.
• Infection spread: Loose areolar layer allows subgaleal empyema to track to eyelids (periorbital edema) or intracranial via emissary veins.
• Hair restoration: Follicular units reside in the skin layer; grafts must include dermal elements for survival.

Understanding these layers guides everything from wound closure to hair transplant technique to neurosurgical access.