Layers of the Scalp

Layers of the Scalp

• The scalp consists of 5 layers, which can be remembered using the word "SCALP"
  • S: Skin (thick, hairy, with sebaceous and sweat glands)
  • C: Connective tissue (containing arteries, veins, nerves, and lymphatics)
  • A: Aponeurosis (a thin, tendon-like structure connecting occipitalis and frontalis muscles)
  • L: Loose areolar tissue (a thin connective tissue layer between the periosteum and epicranial aponeurosis)
  • P: Pericranium (the outer layer of the skull bones)

Clinical Relevance of the Scalp

• Connective tissue layer:
  • Dense, richly vascularized and innervated
  • Contains septa that connect this layer with the layers above and below
  • Wounds do not gape, but may cause profuse bleeding due to adherence of artery walls to connective tissue septa
• Aponeurosis:
  • A strong, fibrous sheet
  • Wounds reaching this layer gape due to muscle contraction
• Loose connective tissue layer:
  • Continuous with the eyelids anteriorly
  • Considered the "dangerous layer" due to emissary veins that can spread infection from the scalp to the cranial cavity
  • May cause a "black eye" if infected

Muscles of the Face

• Occipito-frontalis muscle:
  • Composed of frontal and occipital bellies
  • Originates from the skin of the eyebrows (frontal bellies) and the highest nuchal line (occipital bellies)
  • Inserts into the epicranial aponeurosis
  • Actions: pulls the scalp forward and raises the eyebrows (frontal bellies), and pulls the scalp backward (occipital bellies)
  • Nerve supply: temporal branch of the facial nerve (frontal bellies) and posterior auricular branch of the facial nerve (occipital bellies)

Boundaries of the Face

• Superiorly: the hair margin
• Inferiorly: the lower border of the mandible
• Sideways: from one auricle to the other
• The forehead is common to both scalp and face
• The face has no deep fascia except over the parotid and buccinator muscles

Muscles of Facial Expression

• Orbicularis oculi:
  • Composed of orbital, palpebral, and lacrimal parts
  • Actions: closes the eyelids tightly (orbital part), closes the eyelids gently (palpebral part), and dilates the lacrimal sac (lacrimal part)
  • Supplied by temporal and zygomatic branches of the facial nerve (7th cranial nerve)

Lacrimal Apparatus

• Consists of:
  • Lacrimal gland (secretes tears) and its excretory ducts
  • Lacrimal punctum (opening) and canaliculi (convey tears to the surface of the eye)
• Located in the lacrimal fossa (superior lateral part of the orbital cavity)