Lecture Notes: Anatomy of the Scalp

Introduction

• Scalp Definition: The scalp is the soft tissue covering the skull's vault.
• Boundaries:
  • Anterior: Superciliary arches (eyebrows).
  • Posterior: External occipital protuberance, superior nuchal lines.
  • Lateral: Extends to the zygomatic arch.

Layers of the Scalp

• Mnemonic: SCALP
  • S: Skin
  • C: Connective tissue (dense)
  • A: Aponeurotic layer
  • L: Loose connective tissue
  • P: Pericranium

1. Skin

• Thick and hairy except on the forehead.
• Contains numerous hair follicles and sebaceous glands.
• Common site for sebaceous cysts.
• Contains sweat glands.

2. Connective Tissue (Dense)

• Also known as superficial fascia.
• Dense fibrous tissue binds skin to the underlying muscle.
• Contains blood vessels and nerves.
• Clinical Note: Profuse bleeding when cut, stopped by pressing against bone.

3. Aponeurotic Layer

• Contains the occipitofrontalis muscle.
  • Frontal Belly: Moves scalp, wrinkles forehead, raises eyebrows.
  • Innervation: Temporal branches of the facial nerve (VII).
• Clinical Note: Scalp wounds don't gape unless cut transversely.

4. Loose Connective Tissue

• Separates aponeurotic layer from pericranium.
• Allows free movement of the scalp over the calvaria.
• Clinical Note: Known as the "dangerous area" due to infection spread risk.

5. Pericranium

• The periosteum layer on the outer surface of the skull.
• Loosely attached except at sutures where it is firmly attached.
• Clinical Note: Associated with safety valve hematoma in children.

Clinical Aspects

Surgical Layers of the Scalp

• First three layers (skin, connective tissue, aponeurotic) form the "scalp proper."
• Injury Note: When caught in machinery, the scalp proper can be avulsed.

Black Eye

• Blood and fluid collection after head injury can lead to hematoma.
• Fluid tracks forward causing black discoloration, known as "black eye."
• Common causes include local violence (fist fights).

Other Conditions

• Safety Valve Hematoma: Collection of blood in loose areolar tissue.
• Cephalhematoma: Subperiosteal blood collection.
• Caput Succedaneum: Subcutaneous edema over the presenting head part during birth.