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

#Arrangoiz #HeadandNeckSurgeon #CancerSurgeon #SCALP #ScalpAnatomy #SkinCancer #CASO #CenterforAdvancedSurgicalOncology

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