Anatomy of Head and Neck Muscles

Figure 6.1 Muscles of the head and neck (Reprint from Nouri, K. Complications in Dermatologic Surgery. Philadelphia, PA: Mosby Elsevier; 2008)
Figure 6.1
Muscles of the head and neck
(Reprint from Nouri, K. Complications in
Dermatologic Surgery. Philadelphia,
PA: Mosby Elsevier; 2008
)
(Figure 6.1)
  • Know function of specific function and innervation of head/neck muscles (Table 6-1)
  • Location-specific layers:
    • Scalp has five layers: epidermis/dermis, subcutaneous tissue, musculoaponeurotic layer, loose subaponeurotic tissue and periosteum
    • Facial layers: epidermis, dermis, subcutaneous fat, SMAS and periosteum
  • Superficial musculoaponeurotic system (SMAS)
    • Superficial fibromuscular layer enclosing facial muscles of face/neck; extends from frontalis muscle superiorly to platysma muscle inferiorly, temporalis muscle laterally
    • Allows organized movement of regional muscles during contraction and contributes to appearance of skin tension lines
    • Protective anatomic plane as sensory nerves and axial blood vessels typically located within or between SMAS and subcutaneous fat; motor nerves usually deep to SMAS
    • During facelift, SMAS plicated or pulled to draw skin tight
    • Equivalent of SMAS on scalp is galea aponeurotica, which is a thick inelastic membrane and ideal plane to undermine as it is relatively avascular, separates easily, and results in decreased trauma to neurovascular structures
  • Dissection planes (Table 6-2)
    • Undermining should always take place above SMAS with few exceptions
   
 
Table 6-1 Muscles of Head and Neck
 MuscleFunctionInnervation
 
Occipitalis
Pulls scalp posteriorly
Posterior auricular br. of facial nerve (CN VII)

{Do not confuse with postauricular branch of trigeminal nerve (CNV)}
 
Frontalis muscle
Elevates eyebrows and wrinkles forehead (horizontal forehead lines)
Temporal br. of CN VII
 
Orbicularis oculi
Blinking and tight closure of eyelids (“crow’s feet”), lesser role as brow depressor (depressor supercilii)
Temporal br. of CN VII (upper portion), zygomatic branch of CN VII (lower portion)
 
Corrugator supercilii
Pulls eyebrows medially and downward (vertical glabellar lines)
Temporal br. of CN VII
 
Procerus
Pulls medial portion of eyebrows and glabellar skin downward (horizontal glabellar lines over root of nose)
Zygomatic and buccal br. of CN VII per Bolognia (rare sources say temporal br.)
 
Nasalis
Alar flaring and compression
(“bunny lines” over upper bridge of nose)
Zygomatic and buccal br. of CN VII
 
Levator labii superioris
 
Elevates upper lip
 
Buccal br. of CN VII
 
Levator labii superioris alaeque nasi
Lifts upper lip, dilates nostrils
Buccal br. of CN VII
 
Levator anguli oris
 
Lifts corners of the mouth
 
Buccal br. of CN VII
 
Risorius
Produces smile by drawing back corners of mouth
Marginal mandibular br. of CN VII per Bolognia (other sources say buccal br.)
 
Zygomaticus major
Main contributor to smile: elevates and draws corner of mouth laterally
Buccal br. of CN VII
 
Zygomaticus minor
Elevates upper lip
Buccal br. of CN VII
 
Modiolus
Accounts for cheek dimples in some patients
 
Orbicularis oris
Closes and purses lips
(vertical perioral lip lines)
Buccal or marginal mandibular br. of CN VII
 
Buccinator
Presses cheek against teeth, allows blowing of cheeks
Buccal br. of CN VII
 
Depressor anguli oris
Pulls corner of mouth downward (marionette lines → vertical lines at oral commissure)
Marginal mandibular (MM) br. per Bolognia (most other sources say both MM and buccal br.)
 
Depressor labii inferioris
 
Depresses lower lip
 
Marginal mandibular br. CN VII
 
Mentalis
Protrudes lower lip
Marginal mandibular br. CN VII
 
Platysma
Pulls corner of mouth inferiorly, tenses neck (horizontal neck lines)
Marginal mandibular br (upper portion) and cervical br. CN VII
      
 
   


   
 
Table 6-2 Dissection Planes in Head and Neck
 LocationPlane of Dissection
 
Face
Superficial to SMAS: superficial to mid fat (more superficial in high-risk areas like zygomatic arch, temporal fossa, etc.)
 
Nose
Deep to SMAS: superficial to periosteum or perichondrium (below nasalis muscle)
 
Scalp
Subgaleal plane: superficial to periosteum (below galea aponeurotica), relatively avascular space
 
Trunk/limbs
Deep fat if small excision; just above deep fascia if larger excision