Lecture Notes: Facial Expressions and Muscles

Introduction

• Importance of facial expressions in communication
  • Indicate emotions such as happiness, curiosity, etc.

Scalp Anatomy

• Definition: Layer of skin and subcutaneous tissue covering the cranium
• Extends from: Supraorbital margins (frontal bone) to superior nuchal line (occipital bone)
• Lateral Coverage: Temporal fascia to zygomatic arches
• Five Layers of the Scalp (acronym: SCALP)
  1. Skin
  2. Connective tissue
  3. Aerosis (epicranial aerosis)
  4. Loose connective tissue
  5. Pericranium (periosteum of the cranium)
• First three layers form a single unit called the scalp proper

Muscles of Facial Expression

• Location: Deep in the skin of the scalp, face, and neck
• Attachment: One end to bones/fascia and the other to skin
• Origin: Mesoderm of the second pharyngeal arch
• Innervation: By branches of the facial nerve (Cranial Nerve VII)
  • Branches: Posterior auricular, temporal, zygomatic, buccal, marginal mandibular, cervical
  • Mnemonic: "To Zanzibar by Motor Car"

Key Facial Muscles

1. Occipital Frontalis Muscle

   • Bellies: Frontal (anterior) and Occipital (posterior)
   • Frontal Belly:
     • Origin: Epicranial aerosis
     • Insertion: Skin above eyes/nose
     • Innervation: Temporal nerve
     • Function: Protracts scalp, elevates eyebrows
   • Occipital Belly:
     • Origin: Superior nuchal line of occipital bone
     • Insertion: Epicranial aerosis
     • Innervation: Posterior auricular nerve
     • Function: Draws scalp back

2. Orbicularis Oculi Muscle

   • Parts: Palpebral and Orbital
   • Palpebral Part:
     • Origin: Medial palpebral ligament
     • Insertion: Lateral palpebral ligament
     • Function: Closes eyelids gently (blinking/sleeping)
   • Orbital Part:
     • Origin: Medial orbital margin
     • Insertion: Skin around orbit
     • Function: Closes eyelids tightly (winking)

3. Corrugator Supercilii (Eyebrow muscle)

   • Origin: Medial superciliary arch
   • Insertion: Skin of medial eyebrow
   • Innervation: Temporal nerve
   • Function: Pulls eyebrows medially/inferiorly (frowning)

4. Muscles of the Nose

   • Procerus:
     • Origin: Nasal bone
     • Insertion: Skin between eyebrows
     • Function: Depresses medial ends of eyebrows
   • Nasalis (Two parts):
     • Transverse Part: Narrows nostrils
     • Alar Part: Expands/flairs nostrils
   • Levator Labii Superioris Alaeque Nasi:
     • Origin: Frontal process of maxilla
     • Insertion: Upper lip/nasal cartilage
     • Function: Flares nostrils, raises upper lip

5. Orbicularis Oris Muscle

   • Origin: Maxilla, mandible, angle of mouth
   • Insertion: Mucus membrane of lips
   • Innervation: Buccal nerve
   • Function: Closes mouth, protrudes lips

Upper Lip Muscles

• Muscles: Risorius, Levator Anguli Oris, Zygomaticus Major, Zygomaticus Minor, Levator Labii Superioris
• Functions: Elevate and retract corners of the mouth for smiling/grinning

Lower Lip Muscles

• Muscles: Depressor Anguli Oris, Depressor Labii Inferioris
• Functions: Pull corners downwards for sadness/pouting
• Innervation: Marginal mandibular nerve

Muscle of the Chin: Mentalis

• Origin: Body of mandible
• Insertion: Skin of chin
• Function: Elevates and protrudes lower lip (pouting)

Platysma (Neck Muscle)

• Origin: Supraclavicular and infraclavicular tissue
• Insertion: Base of mandible
• Function: Draws mouth downwards

Buccinator Muscle

• Origin: Alveolar processes of maxilla/mandible, pterygomandibular raphe
• Insertion: Merges with orbicularis oris
• Innervation: Buccal nerve
• Function: Presses cheek against teeth (drinking)

Recap of Key Points

• Scalp Structure: Five layers define it
• Facial Muscles Origin: Mesoderm of second pharyngeal arch
• Muscle Functions: Various facial expressions involve specific muscles
• Innervation: Mostly by facial nerve branches

Conclusion

• Understanding facial muscles is crucial for communication and expression