Scalp and Facial Muscles

Scalp and Facial Muscles

Scalp and Facial Muscles

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Scalp Anatomy - Hairy Headlines

Layers of the Scalp Diagram

The scalp consists of five distinct layers, easily remembered with the 📌 SCALP mnemonic:

  • Skin:
    • Thin, with numerous hair follicles, sebaceous glands, and sweat glands.
    • Rich arterial supply and venous drainage.
  • Connective Tissue (Dense):
    • Anchors skin to the epicranial aponeurosis.
    • Highly vascularized; contains nerves.
    • Lacerations bleed profusely as blood vessels are held open by dense connective tissue.
  • Aponeurosis (Epicranial/Galea Aponeurotica):
    • A strong, tendinous sheet covering the calvaria.
    • Connects the occipitalis and frontalis muscles.
    • Wounds cutting this layer gape widely.
  • Loose Areolar Tissue:
    • Allows free movement of the scalp proper (first three layers) over the pericranium.
    • Contains emissary veins connecting extracranial veins to intracranial dural venous sinuses.
    • Site for fluid collection (e.g., blood in subgaleal hematoma).
  • Pericranium:
    • The external periosteum of the skull bones.
    • Firmly attached to bones, especially at suture lines.
    • Limits spread of subperiosteal hematomas (e.g., cephalhematoma).

⭐ The loose areolar tissue is the 'dangerous area' of the scalp because emissary veins passing through it can transmit infection from the scalp to intracranial dural venous sinuses. This can lead to conditions like cavernous sinus thrombosis or meningitis.

Muscles of Facial Expression - Express Yourself!

  • All muscles of facial expression are derived from the 2nd pharyngeal arch and supplied by the Facial Nerve (CN VII). They are located in the subcutaneous tissue, originating from bone or fascia and inserting into skin.
  • 📌 Facial Nerve (CN VII) branches: To Zanzibar By Motor Car (Temporal, Zygomatic, Buccal, Mandibular, Cervical).

Facial nerve branches and facial muscles

GroupMuscleOriginInsertionNerve (CN VII Branch)Action(s)
OrbitalOrbicularis oculiMedial orbital marginSkin around orbitTemporal, ZygomaticCloses eyelids (blink/wink)
NasalNasalisMaxillaNose (ala/dorsum)BuccalCompresses/flares nostrils
ProcerusNasal boneGlabella skinTemporal, ZygomaticWrinkles nose, draws brows down
OralOrbicularis orisAround mouthLips, modiolusBuccal, MandibularCloses, protrudes lips (kiss)
BuccinatorMaxilla, mandibleModiolus, lipsBuccalCompresses cheek (whistle), aids chew
Zygomaticus majorZygomatic boneAngle of mouthZygomatic, BuccalElevates mouth angle (smile)
Levator Labii SuperiorisInfraorbital maxillaUpper lipZygomatic, BuccalElevates upper lip
Depressor Anguli Oris (DAO)MandibleAngle of mouthMandibularDepresses mouth angle (frown)
RisoriusParotid fasciaAngle of mouth (modiolus)BuccalRetracts mouth angle (grimace)
PlatysmaUpper chest fasciaMandible, lower face skinCervicalTenses neck, depresses lip/jaw

Nerve Supply to Face & Scalp - Face Forward

  • Sensory Supply:

    • Face (Trigeminal N. - CN V):
      • V1 (Ophthalmic): Forehead, upper eyelid, nose.
      • V2 (Maxillary): Midface, lower eyelid, upper lip.
      • V3 (Mandibular): Lower face, chin, lower lip.
    • Scalp:
      • Anterior & Lateral (CN V): Supratrochlear & Supraorbital (V1), Zygomaticotemporal (V2), Auriculotemporal (V3).
      • Posterior (Cervical Nerves): Greater Occipital (C2), Lesser Occipital (C2,C3).
  • Motor - Muscles of Facial Expression (Facial N. - CN VII):

    • 📌 Mnemonic: "To Zanzibar By Motor Car"

Sensory and motor nerve supply of face and scalp

⭐ UMN Facial N. lesion: Contralateral lower face paralysis; forehead spared (bilateral cortical input). LMN lesion: Ipsilateral paralysis of entire half of face (e.g., Bell's Palsy).

  • Arterial:
    • ECA: Superficial temporal, post. auricular, occipital, facial.
    • ICA: Supraorbital, supratrochlear.
  • Venous:
    • Facial v. (valveless) → IJV.
    • To cavernous sinus (ophthalmic v., pterygoid plexus).
  • Lymph: Pre/post-auricular, occipital, submandibular, submental nodes.
  • Clinical:
    • Scalp: profuse bleeding (rich supply, vessels open).
    • ⭐ > Dangerous area of face: infection risk to cavernous sinus (valveless facial/ophthalmic veins). Arterial supply of the scalp and face

High-Yield Points - ⚡ Biggest Takeaways

  • SCALP layers: Loose areolar tissue is dangerous area (infection). Aponeurosis links Frontalis-Occipitalis.
  • Facial muscles: Innervated by CN VII. Bell's Palsy (LMN lesion) → ipsilateral total facial paralysis (forehead included).
  • Face sensory: Trigeminal (CN V). Scalp sensory: Supraorbital (V1), Auriculotemporal (V3), Occipital nerves (C2,C3).
  • Orbicularis oculi (CN VII) closes eye; paralysis → epiphora. Buccinator (CN VII) pierced by parotid duct.
  • Scalp arteries: In dense connective tissue (2nd layer), bleed profusely. From ECA & ICA branches.

Practice Questions: Scalp and Facial Muscles

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In acoustic neuroma, cranial nerve to be involved earliest is

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Flashcards: Scalp and Facial Muscles

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Which layer of the scalp is referred to as the dangerous area of the scalp?_____

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Which layer of the scalp is referred to as the dangerous area of the scalp?_____

Subaponeurotic loose areolar tissue

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