Scalp

Scalp (scalp, derived from Latin scalpere — to cut, scrape) is a layered complex of soft tissues completely covering the calvaria from the frontal brow ridges anteriorly to the upper nuchal line at the occiput.

This multilayered structure performs barrier, cushioning, and thermoregulatory functions, reliably protecting the brain from external influences.

Etiology and pathophysiology

The anatomical structure of this area in international medicine is described using a strict mnemonic rule based on the letters of the English word SCALP, where each letter represents a different functional layer:

1. S (Skin): The outermost layer. Distinctive for its high density, abundance of hair follicles, sebaceous and sweat glands.
2. C (Connective tissue): A dense layer of subcutaneous adipose tissue. Interspersed with rigid fibrous septa, dividing the fat into small lobules. A dense network of blood vessels passes through here.
3. A (Aponeurosis): A tendinous helmet, a strong fibrous plate connecting the frontal and occipital muscles.
4. L (Loose areolar connective tissue): Known as the ‘danger zone’. This space lacks dense partitions, allowing the first three layers to glide freely over the bone.
5. P (Pericranium): The external layer of the skull bones, firmly fused only at the cranial sutures.

The first three layers (skin, connective tissue, and aponeurosis) are firmly bonded and, in injuries (e.g., scalping), detach as a single block precisely over the layer of loose areolar connective tissue.

Clinical significance

The main clinical feature of scalp injuries is profuse arterial bleeding. The blood vessels are tightly woven into the fibrous septa of the second layer. When cut, their walls do not collapse, thus remaining open, which can lead to significant blood loss even with a short wound.

On the other hand, the phenomenally rich blood supply provides the tissues of the calvaria with a very high regenerative potential.