Scalp Anatomy

• The scalp refers to the layers of skin and subcutaneous tissue that cover the bones of cranial vault
• Layers of the Scalp:
  • The scalp consists of five layers
  • The first three layers are tightly bound together:
    • Move as a collective structure
  • The mnemonic ‘SCALP’ can be a useful way to remember the layers of the scalp:
    • Skin
    • Dense Connective Tissue
    • Epicranial Aponeurosis (Galea Aponeurotica)
    • Loose Areolar Connective Tissue
    • Periosteum
  • Skin:
    • Contains numerous hair follicles and sebaceous glands:
      • Thus a common site for sebaceous cysts
  • Dense Connective tissue:
    • Connects the skin to the epicranial aponeurosis
    • It is richly vascularized and innervated
    • The blood vessels within the layer are highly adherent to the connective tissue:
      • This renders them unable to constrict fully if lacerated:
        • And so the scalp can be a site of profuse bleeding
  • Epicranial Aponeurosis:
    • A thin, tendon-like structure that:
      • Connects the occipitalis and frontalis muscles
  • Loose Areolar Connective Tissue:
    • A thin connective tissue layer that:
      • Separates the periosteum of the skull from the epicranial aponeurosis
    • It contains numerous blood vessels, including emissary veins:
      • Which connect the veins of the scalp to the diploic veins and intracranial venous sinuses
  • Periosteum:
    • The outer layer of the skull bones
    • It becomes continuous with the endosteum at the suture lines

• Arterial Supply:
  • The scalp receives a rich arterial supply via the:
    • External carotid artery
    • The ophthalmic artery:
      • A branch of the internal carotid
  • There are three branches of the external carotid artery involved:
    • Superficial temporal artery:
      • Supplies the frontal and temporal regions
    • Posterior auricular artery :
      • Supplies the area superiorly and posteriorly to the auricle
    • Occipital artery:
      • Supplies the back of the scalp
  • Anteriorly and superiorly, the scalp receives additional supply from two branches of the ophthalmic artery:
    • The supraorbital and supratrochlear arteries:
      • These vessels accompany the supraorbital and supratrochlear nerves respectively

• Venous drainage:
  • The venous drainage of the scalp can be divided into:
    • Superficial and deep components
  • The superficial drainage follows the arterial supply:
    • Superficial temporal, occipital, posterior auricular, supraorbital and supratrochlear veins
  • The deep (temporal) region of the skull is drained by:
    • The pterygoid venous plexus:
      • This is a large plexus of veins situated between the temporalis and lateral pterygoid muscles:
        • Drains into the maxillary vein
  • Importantly, the veins of the scalp connect to the diploic veins of the skull:
    • Via valveless emissary veins:
      • This establishes a connection between the scalp and the dural venous sinuses

• Innervation:
  • The scalp receives cutaneous innervation from branches of the:
    • Trigeminal nerve or the cervical nerve roots
  • Trigeminal Nerve:
    • Supratrochlear nerve:
      • Branch of the ophthalmic nerve:
        • Which supplies the anteromedial forehead
    • Supraorbital nerve:
      • Branch of the ophthalmic nerve:
        • Which supplies a large portion of the scalp between the anterolateral forehead and the vertex
    • Zygomaticotemporal nerve:
      • Branch of the maxillary nerve:
        • This supplies the temple
    • Auriculotemporal nerve:
      • Branch of the mandibular nerve:
        • Which supplies skin anterosuperior to the auricle
  • Cervical Nerves:
    • Lesser occipital nerve:
      • Derived from the anterior ramus (division) of C2 and supplies the skin posterior to the ear
    • Greater occipital nerve:
      • Derived from the posterior ramus (division) of C2 and supplies the skin of the occipital region
    • Great auricular nerve:
      • Derived from the anterior rami of C2 and C3 and supplies the skin posterior to the ear and over the angle of the mandible.
    • Third occipital nerve:
      • Derived from the posterior ramus of C3 and supplies the skin of the inferior occipital region

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