Muscular System Part 3 – Tongue, Suprahyoid, Infrahyoid & Pharyngeal Muscles

Intrinsic Tongue Muscles

  • Definition / Key Idea

    • “Intrinsic” = muscles whose origins & insertions are entirely within the tongue; they do not move skeletal structures but alter the tongue’s shape.
    • Provide fine, multi-planar control → speech articulation, swallowing, food bolus manipulation.

  • Global Range of Motion

    • Shortening/lengthening (antero-posterior), widening/narrowing (medio-lateral), thickening/flattening (dorso-ventral).

  • Common Innervation

    • All four sets supplied by CN XII (Hypoglossal nerve).

  • Superior Longitudinal (dorsal; runs antero-posteriorly)

    • Origin : median fibrous septum near epiglottis.
    • Insertion : multiple fibers fan anteriorly across dorsum.
    • Action : shortens & thickens tongue → incidental retraction.
    • Clinical : changes tongue contour; assists in pulling tip back.

  • Inferior Longitudinal (ventral; runs antero-posteriorly)

    • Origin : base of tongue.
    • Insertion : apex.
    • Action : same mechanical effect as superior counterpart but from ventral side.
    • Clinical : combined S-I activity enables tongue tip precision.

  • Transverse (mediolateral)

    • Origin : median fibrous septum.
    • Insertion : lateral borders of tongue.
    • Action : narrows tongue → relative elongation.
    • Clinical : helps create central groove during swallowing.

  • Vertical (dorsal → ventral)

    • Origin : dorsum of tongue.
    • Insertion : ventral surface.
    • Action : flattens & widens tongue.
    • Clinical : key for licking an ice-cream cone; creates broad, flat surface.

Extrinsic Tongue Muscles

  • Definition / Key Idea

    • “Extrinsic” = muscles with one attachment outside the tongue; they move the tongue bodily, change its position, and secondarily alter airway.

  • Skeletal Structures Moved

    • Hyoid bone, mandible, & tongue base are repositioned.

  • Common Innervation

    • All supplied by CN XII.

  • Styloglossus

    • Origin : Styloid process (temporal bone).
    • Insertion : tongue – apex & length lateral to sulcus terminalis.
    • Action : bilateral → retracts tongue; unilateral → deviates tongue ipsilaterally.

  • Hyoglossus

    • Origin : hyoid – greater cornu & body.
    • Insertion : lateral surface of tongue body.
    • Action : depresses and retracts tongue; makes dorsum more convex.

  • Genioglossus

    • Origin : genial tubercles (superior mental spines) – bilateral.
    • Insertion : runs entire length of tongue from base → apex.
    • Action
    • Bilateral : protrudes tongue; depresses central body so apex may curl down (e.g., when sticking tongue out).
    • Unilateral : deviates apex ipsilaterally.
    • Clinical :
    • Weakness → posterior tongue collapse ⇒ obstructive sleep apnea; neuromuscular degeneration endangers airway.

Suprahyoid Muscles

  • Group Concept

    • Lie above hyoid; generally elevate hyoid & floor of mouth, assist mandibular depression, and participate in speech & swallow phases.

  • Shared/Unique Innervations

    • V3 (mandibular division of CN V) → Mylohyoid, anterior belly of Digastric.
    • CN VII → Stylohyoid, posterior belly of Digastric.
    • Cervical C1 fibers via CN XII → Geniohyoid.

  • Mylohyoid

    • Origin : mylohyoid line (mandible).
    • Insertion : mylohyoid raphe & body of hyoid.
    • Action : elevates hyoid, supports & elevates floor of mouth; aids mandibular depression; contracts during speech, mastication & swallowing.
    • Clinical : muscular “diaphragm” forming oral cavity floor.

  • Geniohyoid

    • Origin : genial tubercles (inferior mental spines).
    • Insertion : body of hyoid.
    • Action : elevates & pulls hyoid anteriorly; assists mandibular depression.
    • Clinical : airway patency muscle; relevance to sleep apnea.

  • Stylohyoid

    • Origin : styloid process.
    • Insertion : body of hyoid.
    • Action : elevates & retracts hyoid (elongates floor of mouth).

  • Digastric

    • Posterior belly
    • Origin : mastoid notch (temporal bone).
    • Insertion : intermediate tendon to hyoid.
    • Action : assists mandibular depression; stabilises open jaw – fatigue noteworthy during lengthy dental treatment; contributes to “jaw-drop” surprise expression.
    • Innervation : CN VII.
    • Anterior belly
    • Origin : digastric fossa (mandible).
    • Insertion : same intermediate tendon.
    • Action : elevates hyoid; when hyoid fixed ⇒ retrudes mandible.
    • Innervation : V3.

Infrahyoid Muscles

  • Group Concept

    • Situated below hyoid; generally depress hyoid & larynx, stabilise hyoid during tongue/suprahyoid activity; form muscular ribbon of anterior neck.

  • Common Innervation

    • Ansa cervicalis (C1-C3) of cervical plexus.

  • Omohyoid

    • Origin : clavicle (some texts: superior border of scapula → inferior belly; clavicular fascia → superior belly).
    • Insertion : hyoid.
    • Action : depresses & laterally stabilises hyoid; draws it toward shoulder during head rotation.
    • Clinical : landmark for cervical triangles.

  • Sternohyoid

    • Origin : manubrium (sternum).
    • Insertion : hyoid.
    • Action : depresses hyoid; assists anterior neck stability; aids swallow stages.

  • Sternothyroid

    • Origin : posterior sternum.
    • Insertion : thyroid cartilage (lamina).
    • Action : depresses larynx; pulls hyoid inferiorly indirectly.
    • Clinical : palpated during thyroid exam.

  • Thyrohyoid

    • Origin : thyroid cartilage.
    • Insertion : greater cornu of hyoid.
    • Action : depresses hyoid while elevating larynx (initiating swallow elevation).
    • Clinical : also activated during thyroid palpation.

Pharyngeal Muscles

  • Group Concept & Importance

    • Compose muscular wall of pharynx & soft palate; orchestrate swallowing, airway patency, pressure equalisation; interface between digestive & respiratory tracts.

  • Innervation Overview

    • Vagus (CN X) – majority (pharyngeal plexus).
    • Glossopharyngeal (CN IX) – Stylopharyngeus.
    • V3 – Tensor veli palatini (only palate muscle not by CN X).

Pharyngeal Constrictors (Superior, Middle, Inferior)

  • Origins
    • Superior : pterygoid hamulus, pterygomandibular raphe, mandible, pharyngeal tubercle.
    • Middle : hyoid bone.
    • Inferior : thyroid & cricoid cartilages (laryngeal skeleton).
  • Common Insertion : median pharyngeal raphe (posterior midline seam).
  • Action : sequential constriction creating peristaltic wave propelling bolus into esophagus; elevate pharynx/larynx at onset of swallow.
  • Clinical : form lateral/posterior walls; dysfunction → dysphagia.

Stylopharyngeus

  • Origin : styloid process.
  • Insertion : blends with lateral & posterior pharyngeal walls.
  • Action : elevates & dilates pharynx during swallowing → maintains patent airway while bolus passes.
  • Innervation : CN IX (only skeletal muscle exclusively by IX).

Palatal Muscles (Soft-Palate Movers)

Levator veli palatini
  • (often referenced simply as muscle that elevates soft palate)
  • Origin : inferior surface of temporal bone.
  • Insertion : median palatine raphe.
  • Action : lifts soft palate → seals nasopharynx from oropharynx during swallow; modulates Eustachian tube pressure.
  • Innervation : CN X.
Tensor veli palatini
  • Origin : sphenoid (inferior surface) & auditory tube.
  • Path : wraps around hamulus (acts as pulley).
  • Insertion : median palatine raphe.
  • Action : tenses & lowers soft palate; opens Eustachian tube (equalising ear pressure, “ear-popping”).
  • Innervation : V3.
Musculus uvulae
  • Origin / Insertion : intrinsic – contained within uvula; fibres arise & insert within structure.
  • Action : shortens & broadens uvula.
  • Clinical : helps seal nasopharynx; contributes to speech, saliva expression; hyper-reflex/vomiting; elongated/inflamed uvula linked to bulimia, sleep-apnea.
  • Innervation : CN X.
Palatopharyngeus (forms posterior faucial pillar)
  • Origin : soft palate.
  • Insertion : laryngopharynx & thyroid cartilage.
  • Action : depresses soft palate posteroinferiorly; elevates posterior faucial pillar anterosuperiorly.
  • Innervation : CN X.
Palatoglossus (forms anterior faucial pillar)
  • Origin : median palatine raphe (posterior part).
  • Insertion : lateral base of tongue.
  • Action : elevates tongue base toward soft palate & simultaneously depresses soft palate toward tongue; during swallow pushes bolus past pillars into oropharynx while blocking nasopharynx.
  • Innervation : CN X.

Key Landmarks & Connective Tissue Raphe

  • Posterior faucial pillar : formed by Palatopharyngeus.
  • Anterior faucial pillar : formed by Palatoglossus.
  • Pterygomandibular raphe : fibrous band between hamulus & mandible; origin for Buccinator; visible intra-orally as pterygomandibular fold.
  • Median palatine raphe : fibrous seam over palatine suture; origin for Palatoglossus & insertion for Levator/Tensor veli palatini.

Inter-Group Functional Connections & Clinical Pearls

  • Suprahyoids + Infrahyoids act as antagonistic ribbon stabilising hyoid—necessary anchor for extrinsic tongue movements & swallow phases.
  • Pharyngeal-palatal synergy ensures tri-sealing of oral cavity, oropharynx, nasopharynx according to functional demand (speech vs. swallow vs. respiration).
  • Sleep apnea pathophysiology: weakness of Genioglossus & Geniohyoid allows posterior tongue collapse; uvular hypertrophy exacerbates obstruction.
  • Dental relevance:
    • Digastric & Mylohyoid fatigue with prolonged mouth opening.
    • Pterygomandibular raphe landmark for inferior alveolar nerve blocks.
    • Palpating thyroid utilises Sternothyroid/Thyrohyoid contraction.
  • Swallow Stages (muscle highlights)
    1. Oral : Intrinsic + Genioglossus shape & propel bolus.
    2. Pharyngeal : Palatoglossus contracts → bolus enters oropharynx; Levator veli palatini elevates palate; Constrictors drive bolus.
    3. Esophageal : Constrictors relax sequentially as peristalsis continues.

Numerical / Statistical / Miscellany

  • No specific numeric data in transcript except page references; however remember cranial nerve designations correspond to Roman numerals:
    • X=10X = 10 (Vagus)
    • IX=9IX = 9 (Glossopharyngeal)
    • XII=12XII = 12 (Hypoglossal)
    • VII=7VII = 7 (Facial)
    • V3=5(mandibular division)V3 = 5_{(mandibular\,division)}
    • Cervical plexus roots C1-C3C1\text{-}C3 form Ansa cervicalis.