Pharynx and Larynx Lecture

Pharynx – Structure and Regions

• Conduit that connects nasal & oral cavities to both esophagus (posterior) and trachea (anterior)

• Divided into three functional sections:

  • Nasopharynx: immediately posterior to the nasal cavity and above the soft palate

  • Purely respiratory in function

  • Oropharynx: posterior to the oral cavity

  • Shared passage for air and food

  • Laryngopharynx (Hypopharynx): mainly posterior to the larynx; continuous with esophagus

Mucosal Folds, Tonsils, & Surface Landmarks

• Pharyngeal mucosa is a continuation of oral mucosa

• Key folds (with underlying muscles):

  • Salpingopharyngeal fold

  • Extends from opening of the auditory (Eustachian) tube ("salpinx" = horn)

  • Contains salpingopharyngeus m.; elevates pharynx during swallowing

  • Palatoglossal fold

  • Covers palatoglossus m. (palate → tongue)

  • Palatopharyngeal fold

  • Covers palatopharyngeus m. (palate → pharynx)

• Palatine tonsil

  • Lymphoid tissue lodged between palatoglossal & palatopharyngeal folds

  • Supplied by dense palatine arterial & venous plexus → surgical risk for bleeding during tonsillectomy

• Glossopharyngeal n. (CN IX) pierces pharyngeal wall between superior & middle constrictors to supply posterior 1⁄3 of tongue (sensory + taste)

Muscles of the Pharynx

Circular (Constrictor) Layer

External; sequentially contract to propel bolus

• Superior constrictor

  • Origin: pterygoid hamulus & pterygomandibular raphe

  • Inserts posteriorly into pharyngeal raphe

• Middle constrictor

  • Origin: hyoid bone

• Inferior constrictor

  • Origin: thyroid & cricoid cartilages

Longitudinal Layer

Elevate & shorten pharynx during swallowing

• Palatopharyngeus m. – CN X (vagus)

• Salpingopharyngeus m. – CN X (vagus)

• Stylopharyngeus m. – only pharyngeal muscle innervated by CN IX

Larynx – General Functions & Cartilages

• “Voice box”; produces sound, guards airway, enables Valsalva maneuver (glottal closure → ↑ thoraco-abdominal pressure for lifting, defecation, childbirth)

• Composed of 9 cartilages (3 unpaired, 3 paired)

Unpaired Cartilages

• Thyroid cartilage

  • Two laminae meet at midline → laryngeal prominence (Adam’s apple)

  • Superior & inferior horns; inferior horns articulate with cricoid cartilage

• Cricoid cartilage

  • Only complete ring (taller posteriorly, narrow anteriorly)

• Epiglottis

  • Leaf-shaped; folds posteriorly during swallowing to protect airway

Paired Cartilages

• Arytenoid (apex, vocal process, muscular process)

• Corniculate (sits atop arytenoid apex)

• Cuneiform (embedded in aryepiglottic fold; often unseen)

Membranes & Ligaments

• Thyrohyoid membrane: hyoid ↔ thyroid cartilage

• Cricothyroid ligament (membrane): cricoid ↔ thyroid; surgical access site in emergency airway

• Vocal ligament: arytenoid (vocal process) → thyroid; covered by mucosa → true vocal fold

• Conus elasticus (lateral cricothyroid membrane): cone-shaped extension from vocal ligament to cricoid rim; reinforces “roof” of upper trachea

• Quadrangular membrane: epiglottis → arytenoid; its inferior thick margin = vestibular ligament (becomes false vocal fold); superior margin forms aryepiglottic ligament (→ aryepiglottic fold)

Internal Cavities & Landmarks

• Vestibule: space above vestibular folds

• Ventricle: recess between vestibular & vocal folds

• Infraglottic cavity: below vocal folds to trachea

• Rima glottidis: slit-like opening between right & left true vocal folds; width changes with respiration, phonation, Valsalva

Intrinsic Muscles of the Larynx & Actions

(All recurrent laryngeal n. except where noted)

• Cricothyroid – external laryngeal n. (branch of superior laryngeal)

  • Tilts thyroid cartilage forward (like fire-truck hood) → lengthens & tenses vocal folds → raises pitch

• Thyroarytenoid

  • Pulls thyroid posteriorly → shortens & relaxes vocal folds → lowers pitch

  • Deep fibers = vocalis m. (fine tension control; removes slack when thyroid retracts)

• Posterior cricoarytenoid

  • Only abductor of vocal folds; rotates arytenoid laterally → opens rima glottidis (critical for breathing)

• Lateral cricoarytenoid

  • Adducts vocal folds; rotates arytenoid medially → closes rima glottidis

• Arytenoid (transverse & oblique fibers)

  • Draw arytenoid cartilages together; further adduction/seal of posterior glottis

Neurovascular Supply

Arteries

• Superior laryngeal a. (from superior thyroid a.)

  • Pierces thyrohyoid membrane with internal laryngeal n.; supplies mucosa above vocal folds (vestibule)

• Inferior laryngeal a. (branch of inferior thyroid a.)

  • Descends with recurrent laryngeal n.; supplies region below vocal folds

Nerves

• Superior laryngeal n. (from CN X)

  • Internal branch: sensory to mucosa above vocal folds (no motor)

  • External branch: motor to cricothyroid m.

• Recurrent laryngeal n. → Inferior laryngeal n.

  • Motor to all other intrinsic laryngeal muscles

  • Sensory to mucosa below vocal folds

Functional & Clinical Correlates

• Valsalva maneuver

  • True vocal folds adduct → rima glottidis sealed → ↑ intrathoracic & intra-abdominal pressure (weight-lifting, defecation, childbirth)

• "Something went down the wrong pipe"

  • Failure of epiglottis & laryngeal closure reflex → aspiration; among body’s strongest reflexes

• Tonsillectomy complications

  • High risk of hemorrhage from palatine arterial/venous plexus

• Emergency airway (cricothyrotomy)

  • Incision through cricothyroid membrane when upper airway obstructed; avoids vascular thyrohyoid region

• Unilateral recurrent laryngeal n. injury

  • Hoarseness due to impaired abduction/adduction on one side

• Bilateral posterior cricoarytenoid paralysis

  • Airway obstruction (inability to abduct vocal folds) → life-threatening

Innervation Summary Cheat-Sheet

• Pharyngeal muscles:

  • All CN X except stylopharyngeus (CN IX)

• Laryngeal muscles:

  • All recurrent laryngeal (inferior laryngeal) except cricothyroid (external laryngeal)

Quick Reference of Key Terms

• Rima glottidis = space between true vocal folds

• True vocal fold = mucosa-covered vocal ligament; vibrates to produce sound

• False vocal fold (vestibular fold) = mucosa-covered vestibular ligament; protective, not phonatory

• Vestibule / Ventricle / Infraglottic cavity = supraglottic → transglottic → subglottic subdivisions

• Conus elasticus = lateral cricothyroid membrane forming elastic cone below vocal folds