scalp

scalp

[skalp]
scalp, the integument covering the top of the head. It consists of three layers of tissue: the skin, an underlying layer of tissue and blood vessels, and the occipitofrontalis muscle stretching from the eyebrows to the back of the head. Except for its abundant growth of hair, the skin of the scalp resembles that of the rest of the body but is especially rich in blood vessels. Hence profuse bleeding may be associated with scalp injuries.

The scalp is the anatomical area bordered by the face anteriorly and the neck to the sides and posteriorly.

Layers

It is usually described as having five layers, which can be remembered with the mnemonic "SCALP":

  • S: The skin on the head from which head hair grows. It is richly supplied with blood vessels.
  • C: Connective tissue. a thin layer of fat and fibrous tissue lies beneath the skin
  • A: The aponeurosis (or galea aponeurotica) is the next layer. It is a tough layer of dense fibrous tissue which runs from the frontalis muscle anteriorly to the occipitalis posteriorly
  • L: The loose areolar connective tissue layer provides an easy plane of separation between the upper three layers and the pericranium. In scalping the scalp is torn off through this layer. It also provides a plane of access in craniofacial surgery and neurosurgery. This layer is sometimes referred to as the "Danger Zone" because of the ease by which infectious agents can spread through it to emissary veins which then drain into the cranium. The loose areolar tissue in this layer is made up of random collagen I bundles, collagen III and is highly vascular and cellular. It will also be rich in glycosaminoglycans (GAGs) and will be constituted of more matrix than fibers.
  • P: The pericranium is the periosteum of the skull bones and provides nutrition to the bone and the capacity for repair. It may be lifted from the bone to allow removal of bone windows (craniotomy).

The clinically important layer is the aponeurosis. Scalp lacerations through this layer mean that the "anchoring" of the superficial layers is lost and gaping of the wound occurs; this requires suturing. This can be achieved with simple or vertical matress sutures using a non-absorbable material, which are subsequently removed at around day 7. Remember thorough wound irrigation and tetanus care for dirty wounds.

Blood supply

The blood supply of the scalp is via five pairs of arteries, three from the external carotid and two from the internal carotid:

  • internal carotid
    • the supratrochlear artery to the midline forehead. supratrochlear artery is a branch of ophthalmic branch of the internal carotid artery.
    • the supraorbital artery to the lateral forehead and scalp as far up as the vertex. supraorbital artery is a branch of ophthalmic branch of the internal carotid artery.
  • external carotid

Innervation

The scalp is innervated by the following:

There are no lymph nodes in the scalp; lymphatic drainage is to the pre- and post-auricular nodes.

Role in aesthetics

The scalp plays an important role in the aesthetics of the face. Androgenic alopecia, or male pattern hair loss, is a common cause of concern to men. It may be treated by medication (eg finasteride) or hair transplantation with variable success. If the scalp is heavy and loose, a common change with aging, the forehead may be low, heave and deeply lined. The brow lift procedure aims to address these concerns.

Pathology

The scalp is a common site for the development of tumours including:

Scalp conditions

See also

  • Trichology -- the scientific study of hair and scalp
  • Trichodynia -- burning scalp syndrome
  • Scalping -- the act of removing the scalp, usually with the hair, as a portable proof or trophy of prowess in war.

Additional images

References

External links

  • - "Integument: scalp, transverse"
  • - "Integument: scalp"
  • http://www.dartmouth.edu/~humananatomy/figures/chapter_47/47-1.HTM

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