Pharynx/Pharyngeal/Masticatory Muscles

• Pharynx


  • Oval tube, larger side to side than front to back
  • Connective tissue predominates at the top, muscle predominates at the bottom
  • Continuous with esophagus at lower end
• Pharynx


  Three cavities: nasopharynx, oropharynx, laryngopharynx
• Nasopharynx contains the auditory tubes and nasopharyngeal tonsils (adenoids)
• Oropharynx contains the palatine tonsils and lingual tonsil
• Pharyngeal tube


  • Three layers: fibrous, muscular, mucous
  • Aponeurosis attached to base of skull anterior to foramen magnum
  • Pharyngeal muscles attached to this aponeurosis
• Constrictors


  Three pairs of muscles that reduce the diameter of a portion of the pharyngeal cavity
• Superior Constrictor


  • Weakest but most complex
  • Forms nasopharyngeal and upper oropharyngeal walls
  • Origin: sphenoid, mandible, pterygomandibular ligament
  • Course: posterior, then medial
  • Insertion: midline raphe
  • Action: may contribute to velopharyngeal closure by moving posterior wall of pharynx anteriorly
• Middle Constrictor


  • Somewhat fan shaped
  • Origin: hyoid bone
  • Course: fan out posteriorly and medially
  • Insertion: midline raphe
  • Action: reduce diameter of pharynx
• Inferior Constrictor - Thyropharyngeus


  • Inferior Constrictor is thickest and strongest of constrictor muscles
  • Thyropharyngeus is the majority of the Inferior Constrictor
  • Origin: thyroid cartilage
  • Course: fans out posteriorly and medially
  • Insertion: midline raphe
  • Action: reduce diameter pharynx
• Inferior Constrictor - Cricopharyngeus

  • Part of Inferior constrictor
  • Muscular component of upper esophageal sphincter (UES)
  • Origin: cricoid cartilage
  • Course: fans out posteriorly and medially
  • Insertion: midline raphe
  • Action: open and close upper esophageal sphincter
• Constrictor muscle actions


  • Pull pharyngeal walls inward and forward to constrict the pharyngeal tube
  • Cricopharyngeus also assists in closing the upper esophageal sphincter

  
• Stylopharyngeus

  • Long thin muscle
  • Origin: styloid process of temporal bone
  • Course: inferior, entering between superior and middle constrictor
  • Insertion: blend with constrictors, with some fibers inserting on thyroid cartilage
  • Action: elevate and dilate pharynx

  
• Salpingopharyngeus

  • Short thin muscle
  • Origin: lower border of the pharyngeal orifice of the Eustachian tube
  • Course: inferior, deep to superior constrictor
  • Insertion: blends with fibers of palatopharyngeus muscle
  • Action: elevate and dilate pharynx

  
• Palatopharyngeus/Pharyngopalatine

  • Also known as Pharyngopalatine
  • Posterior faucial pillar
  • Longer muscle
  • Origin: soft palate
  • Course: superior through posterior faucial pillar
  • Insertion: lateral walls of pharynx, thyroid cartilage
  • Action: principally to guide material through pharynx, may contribute to palatal lowering and VP seal

  
• Most of the pharyngeal muscles constrict (reduce the diameter) of the pharynx
• The Stylopharyngeus and Salpingopharyngeus elevate and dilate (increase the diameter) of the pharynx
• The Cricopharyngeus also helps to close the Upper Esophageal Sphincter
• The three major constrictor muscles are the Superior, Middle and Inferior constrictors. The inferior constrictor is divided into the Thyropharyngeus and the Cricopharyngeus.
• Temporomandibular Joints

  • Only skeletal joint in articulatory system
  • Condoyle of mandible fits into cavity in temporal bone, separated by an articular disk
  • Joint is surrounded by fibrous capsule and lubricated with synovial fluid
• Motions of the mandible possible with the TMJ


  • Elevation
  • Depression
  • Protrusion
  • Retraction
  • Lateral Motion
• Elevation


  Jaw closing
• Depression


  Jaw opening
• Protrusion


  Mandible moving anteriorly
• Retraction


  Mandible moving posteriorly
• Lateral Motion


  Side-to-side motion
• Masticatory Muscles

  • Depressors
  • Elevators
• Digastric

  • Paired muscle, each consisting of 2 fleshy bellies connected by the intermediate tendon between them
  • With hyoid bone fixed, contraction assists in depressing mandible
• Mylohyoid

  • Thin sheet of muscle fibers forming muscular floor of mouth
  • With hyoid bone fixed, contraction assists in depressing mandible
  • Comparatively small effect on jaw
• Geniohyoid

  • Paired cylindrical muscle located just superior to mylohyoid
  • With hyoid bone fixed, contraction assists in depressing mandible
• External Pterygoid


  • Also known as Lateral pterygoid
  • Has superior & inferior belly
  • Protrude (and depress) mandible by sliding condyle down and forward
  • Unilateral contraction produces grinding action
• Masseter

  • Most powerful masticatory muscle
  • Has two layers - internal and external
  • Outer Layer: elevate jaw
  • Inner Layer: elevate and retract jaw

  
• Temporalis

  • Broad, thin muscle on side of skull, overlying temporal bone
  • Anterior and middle fibers: elevate jaw
  • Posterior fibers: elevate and retract jaw
• Internal Pterygoid


  • Also known as Medial pterygoid
  • Thick, quadrilateral muscle
  • Elevate jaw
  • With masseter, forms mandibular sling, strapping mandible to skull

  
• Masticatory muscles are primarily elevators or depressors of the jaw
• Most of the depressors of the jaw are suprahyoid muscles where the origin and insertion were reversed
• The external pterygoid muscle is a jaw depressor that is not a suprahyoid muscle
• The masseter, temporalis and internal pterygoid muscles are the jaw elevators