Facial Muscles

• Lips


  Most mobile part of the face
• Lips


  • Acted upon by many facial muscles
• Orbicularis Oris


  Principal muscle acting on lips
• Orbicularis Oris


  • Sphincter muscle that completely encircles mouth opening
  • Composed of fibers from other facial muscles, as well as fibers exclusive to the lips
  • Many facial muscles tie into the OO
  • Action – closes mouth and puckers lips

  
• Facial ExpressionMuscle Groups

  • Categorized on the basis of orientation
  • Orbicularis Oris
  • Transverse
  • Angular
  • Vertical

  
• Transverse muscles


  • Course horizontally from origin and insert into orbicularis oris
  • Act to pull lips against teeth
  • Facilitate compression of lips
• Angular muscles


  • Approach corners of mouth obliquely from above or below
  • Smiling or frowning
• Vertical muscles


  • Enter corners of mouth from directly above or below
  • Facial expression, and compress mouth corners
• Buccinator


  • Principal muscle of cheek
  • Deepest muscle of face
  • Origin – pterygomandibular ligament
  • Course – horizontal, and anterior
  • Insert – blend with fibers of upper and lower lip
  • Some fibers decussate (crisscross) such that inferior fibers enter upper lip and superior fibers enter lower lip
  • Action – Compress lips and cheeks against teeth, Draw mouth corners laterally

  
• Risorius


  • Highly variable
  • Origin – fascia covering masseter
  • Course – parallel and superficial to buccinator
  • Insertion – skin and mucosa at mouth corner
  • Action – assist in drawing mouth corner laterally

  
• Zygomatic Major


  • Origin – surface of zygomatic bone
  • Course – inferior, medial
  • Insertion – orbicularis oris and skin at mouth corner
  • Action – draw mouth corner superiorly and laterally (broad smile)

  
• Levator Labii Superior


  • Origin – lower margin of orbit
  • Course – inferior
  • Insertion – upper lip
  • Medial to levator anguli oris
  • Action – Elevator of upper lip
• Depressor Labii Inferior


  • Located beneath lower lip, just lateral to midline
  • Origin – mandible, lateral to mental tubercles
  • Course – superior and medial
  • Insertion – lower lip
  • Action – draw lower lip inferiorly and laterally
• Levator Anguli Oris


  • Origin – lateral to nasal ala
  • Course – inferior
  • Insertion – orbicularis at mouth corner, some fibers crossing into lower lip
  • Action – draw corner of mouth superiorly, also assist in mouth closing by drawing lower lip (corner) superiorly
• Depressor Anguli Oris

  • Superficial to depressor labii inferior
  • Origin – mandible, lateral to mental tubercles
  • Course – superior
  • Insert – orbicularis at mouth corner, some fibers crossing into upper lip
  • Action – depress lip angle, also assist in mouth closing by drawing upper lip (corner) inferiorly
• Mentalis


  • Origin – mental tuberosity of mandible
  • Course – superior
  • Insertion – some fibers into skin on the chin, some into orbicularis oris
  • Action – wrinkle chin, evert (protrude) lower lip

  
• Lip Muscle Actions


  • Pulling Lips Apart
  • Pushing Lips Together
  • Compressing Lips
• Orbicularis Oris


  Muscle of facial expression

  
• Types of facial expression muscles


  • Orbicularis Oris
  • Transverse
  • Angular
  • Vertical

  
• Extrinsic Muscles


  • Genioglossus
  • Styloglossus
  • Hyoglossus
  • Palatoglossus
• Intrinsic Muscles


  • Superior Longitudinal
  • Inferior Longitudinal
  • Vertical
  • Transverse
• Masticatory Muscles


  • Two categories: Elevators and Depressors
  • Some suprahyoid muscles fall into the Depressor category
• Other Muscles of Facial Expression


  • Three categories: Transverse, Angular, Vertical

  
• Extrinsic Muscles


  • Primarily responsible for gross movement of the tongue
• The tongue is the most important and most active of the articulators
• The tongue modifies the shape of the oral cavity
• The tongue is a hydrostat - can change shape but not volume/size
• Muscles change the shape, not size, of the tongue to alter the shape of the oral cavity
• Divisions of the tongue from a functional (articulation) perspective

  • Tip
  • Blade
  • Dorsum
  • Root
  • Body
• The tongue has a longitudinal median sulcus that divides the dorsum into right and left halves
• The tongue has a foramen cecum, a small pit towards the back
• The tongue has papillae, projections of dermis covering the dorsum that give it a rough texture and contain taste buds
• The dorsum is the top surface of the tongue
• Genioglossus

  Strongest and largest tongue muscle, forms bulk of tongue tissue, origin at mental spines of mandible, inserts into hyoid and tongue dorsum, action is to pull tongue downward
• The genioglossus has posterior fibers that draw the tongue forward to protrude the tip, and anterior fibers that may retract the tongue tip
• Styloglossus

  Small, fan-shaped muscle that originates from the styloid process, inserts into the sides of the tongue near the dorsum, action is to draw the tongue posteriorly and superiorly

  
• Hyoglossus

  Originates from the hyoid bone, inserts into the lateral submucous tissue of the posterior half of the tongue, action is to retract and depress the tongue
• Palatoglossus

  Also known as the Glossopalatine, originates from the palatal aponeurosis, inserts into the sides of the tongue, action is to exert an upward pull on the tongue if the velum is anchored
• The tongue has two "skeletal" structures - a fibrous midline septum and a connective tissue "bag" just deep to the epidermis, which provide attachment points for the intrinsic muscles
• Inferior Longitudinal


  Fibers lie on the undersurface of the tongue, lateral to the genioglossus, originates from the tongue root and perhaps the hyoid bone, inserts by blending with other fibers from root to apex, action is to shorten the tongue and pull the tip down