Cranial Fossa (ACF) & Layers of Scalp

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”Mneumonic:
  • Fucking
    • Anterior → thudakkam
      • Frontlum Backlum Ethi (Ant and Post Ethmoid) Mavakkum (Middle Meng A)
    • Middle → Ass middle (Accessory middle mening, middle mening, mening) akum
    • Posteriorly → Last → Penis into Vagina (Vertebral), then Oral (Occipital) then Swallow (Ascending Pharyngeal)

Anterior Cranial Fossa (ACF)

Nerve Supply (Meningeal Branches):

  • V1: Ophthalmic nerve
    • Anterior and posterior ethmoidal nerve
  • V2: Maxillary nerve
  • V3: Mandibular nerve

Arterial Supply:

  • Internal carotid artery
    • Ophthalmic artery
      • Anterior and posterior ethmoidal artery
  • External Carotid Artery
    • Middle meningeal artery

Middle Cranial Fossa (MCF)

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  • Nerve Supply (Meningeal Branches):
    • Meningeal branch of ethmoidal nerve (V1)
    • Meningeal branch of maxillary nerve (V2)
    • Meningeal branch of mandibular nerve (V3)
    • Tentorial nerve: Branch of ophthalmic nerve (V1)
    • C1 fibres distributed by CN-12
    • C2, C3 fibres distributed by CN-10
  • Arterial Supply:
    • External carotid artery
      • Maxillary artery
        • Accessory middle meningeal artery
        • Middle meningeal artery
    • Internal carotid artery
      • Meningeal branch
    • Ascending pharyngeal artery

Posterior Cranial Fossa (PCF)

  • Nerve Supply (Meningeal Branches):
    • V1: Ophthalmic nerve
      • Tentorial branch
    • Hypoglossal nerve: C1 fibres
    • Vagus nerve: C2, C3 fibres
  • Arterial Supply:
    • Vertebral artery
    • Occipital artery
    • Ascending pharyngeal artery

Layers of Scalp

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1. Skin

  • Thick
  • Connected to aponeurotic by connective tissue
  • Content: Hair, sebaceous, and sweat glands

2. Connective Tissue

  • Blood vessel walls tightly adherent to stroma
  • Lacerations bleed heavily (cannot vasoconstrict)
  • Applied aspect: Injury → Profuse bleeding

3. Aponeurotic Layer

  • Galea Aponeurotica
  • Content:
    • Frontal belly (of occipitofrontalis)
    • Occipital belly

Surgical layer:

  • Skin + Connective Tissue + Aponeurotic Layer (Galea Aponeurotica)
  • Easy plane of cleavage
  • Tissue expanders/implants are placed under this layer
  • Subaponeurotic bleeding → "Black eye"
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Frontal Belly
Occipital Belly
Origin
Skin of eyebrow & nose
(bony origin)
Superior nuchal line: Lateral 2/3rd
Nerve supply
Temporal branch of 7th nerve
Posterior auricular branch of 7 CN

4. Loose Areolar Tissue (Danger Area of Scalp)

  • Retrograde infection via emissary veins
    • Emissary veins (valveless) → Scalp veins ⇔ Dural venous sinuses → Cavernous sinus thrombosis
  • Bidirectional flow:
    • → If intracranial pressure ↑
    • ← If intracranial pressure ↓
  • Applied aspect:
      1. Infection of scalp spreads to Dural venous sinuses
      1. Injury
          • Blood doesn't move posteriorly/laterally (bony origin of occipital belly)
          • Collects under loose areolar layer
          • Gravitates anteriorly (frontal belly) → Black eye

5. Pericranium

  • Periosteum
  • Loosely arranged (except at sutures)