Scalp Anatomy Lecture Notes

Introduction to Scalp

• The scalp is the soft tissue covering the vault of the skull.
• Extends:
  • Anteriorly from the eyebrows (super ciliary arches).
  • Posteriorly to the external occipital protuberance and superior nuchal lines.
  • Laterally and inferiorly to the zygomatic arch.

Layers of the Scalp

The layers can be remembered by the acronym SCALP:

1. Skin

   • Thick, hairy (except forehead).
   • Contains hair follicles, sebaceous glands, and sweat glands.
   • Common site for sebaceous cysts.
   • Estimated 120,000 hairs; 20-100 lost daily.
   • Baldness often affects males and some elderly females.

2. Connective Tissue (Dense)

   • Dense fibrous tissue (superficial fascia) binding skin to underlying structures.
   • Contains blood vessels and nerves.
   • Clinical note: Profuse bleeding when cut due to open vessels; can be stopped by pressure.

3. Aponeurotic Layer

   • Consists of occipitofrontalis muscle.
   • Frontal belly (anterior), occipital belly (posterior) connected by aponeurosis (epicranial aponeurosis or galea aponeurotica).
   • Innervated by facial nerve (7th cranial).
   • Clinical note: Scalp wounds don’t gape unless aponeurosis is cut transversely.

4. Loose Connective Tissue

   • Facilitates scalp movement; consistency allows infection spread.
   • Contains emissary veins; infections can spread to intracranial dural venous sinuses.
   • Known as the "dangerous layer" due to risk of infection spreading.

5. Pericranium

   • Periosteum on the calvaria; loosely attached except at sutures.
   • Can be stripped off the bone; firmly attached at sutural lines.

Clinical Correlations

• Scalp Proper:

  • First three layers form the scalp proper; cannot be separated.
  • Free mobility due to loose areolar tissue.

• Black Eye:

  • Blood/fluid collects in loose areolar tissue; can lead to hematoma and discoloration around eyes.
  • Commonly caused by local violence (e.g., fist fights).

• Safety Valve Hematoma:

  • In children, cranial fractures may lead to blood collection in sub-aponeurotic space, delaying cerebral compression symptoms.

• Cephalhematoma:

  • Subperiosteal blood collection, commonly in parietal region.

• Caput Succedaneum:

  • Subcutaneous edema over head at delivery, common birth trauma.

Summary

• The scalp's complex structure and its clinical importance highlight its role in protecting the skull and its susceptibility to trauma and infection.
• Understanding the scalp layers and their functions is crucial for medical professionals dealing with head injuries and conditions affecting the scalp.