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Anatomy of Skull and Spine

Outer 3 layers are often torn off as a unit in accidents; wounds do not gape if epicranius (occipitofrontal) m. not involved

Area: from supraorbital ridge to superior nuchal line, laterally to zygomatic arch and external auditory meatus 3 primary muscle groups: frontalis, occipitalis, temporalis

  1. SKIN
    • linear hyperattenuating structure
  2. SUBCUTIS
    = fibroadipose tissue closely adherent to skin and underlying epicranius
    • thick layer of fat attenuation
  3. GALEA APONEUROTICA
    = layer of thick fibrous tissue continuous with epicranius (occipitofrontal) muscle consisting of
    1. frontal muscle belly + auricularis m. anteriorly
    2. occipital muscle belly posteriorly

    forming centrally the large epicranial aponeurosis
    • thin line of increased attenuation temporalis fascia
  4. SUBGALEAL SPACE
    = subaponeurotic areolar tissue between periosteum of outer table and galea aponeurotica
    Histo: analogous to loose areolar tissue containing fat
    • allows the 3 superficial layers of scalp to move as a unit on the cranium enabling the scalp to wrinkle
    • allows fluid to accumulate and spread across the cranium analogous to intracranial subdural fluid collections
  5. PERICRANIUM = periosteum of outer table
    • firmly adheres to margins of underlying skull bones at suture lines
    • usually not visible by CT without subperiosteal hematoma
  6. SUBPERIOSTEAL SPACE
    = potential space created when periosteum of outer table becomes detached from calvaria (= cephalohematoma); analogous to intracranial extradural hematoma