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🫁 LARYNX - Comprehensive Exam Notes

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Anatomy of the Larynx - Bailey & Love's view

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1. Introduction & Functions

• Protection of lower airway via:
  • Closure of the laryngeal inlet
  • Closure of the false cords (vestibular folds)
  • Closure of the glottis
  • Cessation of respiration
  • Cough reflex
• Phonation - vocal folds produce sound by quasiperiodic vibration
• Respiration - control of airway diameter
• Effort closure - fixes thorax to stabilize trunk (heavy lifting, Valsalva, defecation)

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2. Cartilaginous Framework

Unpaired Cartilages (3)

Paired Cartilages (3 pairs)

Exam tip: Thyroid, cricoid, most of arytenoid = hyaline cartilage (may ossify with age). Epiglottis, corniculate, cuneiform, vocal process of arytenoid = elastic cartilage (never ossifies).

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3. Joints of the Larynx

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4. Membranes & Ligaments

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5. Divisions of the Larynx (VERY HIGH YIELD)

Laryngeal Inlet
      ↓
 VESTIBULE (supraglottis)
      ↓
Vestibular folds (false cords) — pink mucosa
      ↓
 MIDDLE CAVITY (laryngeal ventricle bulges laterally)
      ↓
Vocal folds (true cords) — WHITE appearance
      ↓
 INFRAGLOTTIC SPACE (subglottis)
      ↓
Trachea

Rima glottidis = space between the vocal folds. V-shaped (meeting anteriorly at thyroid angle; separated posteriorly at arytenoids). True vocal folds are WHITE in color (avascular stratified squamous epithelium).

Laryngocele: Abnormal distension of the saccule due to increased intraglottic pressure (seen in horn players, glass blowers) or obstruction by tumor/inflammation. Internal laryngocele stays inside thyrohyoid space; external (mixed) laryngocele pierces thyrohyoid membrane and presents as neck swelling.

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6. Intrinsic Muscles of the Larynx (HIGHEST YIELD)

MNEMONICS:

• "PCA is the lifesaver" - Posterior CricoArytenoid is the only Abductor. If both are paralyzed → stridor + respiratory distress.
• "All muscles Adduct, only PCA Abducts"
• Cricothyroid = extrinsic to larynx (outside larynx proper) → supplied by eSLN, NOT RLN.

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7. Nerve Supply (VERY HIGH YIELD)

• Right RLN: Loops under right subclavian artery → shorter intrathoracic course
• Left RLN: Loops under arch of aorta → longer intrathoracic course → more vulnerable to mediastinal pathology (aortic aneurysm, lung cancer, enlarged nodes)

Human communicating nerve: Anastomosis between eSLN and RLN, seen in ~70% of larynges - provides sensory supply to subglottis and motor to thyroarytenoid.

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8. Blood Supply

The superior laryngeal artery and internal branch of SLN pierce the thyrohyoid membrane together.

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9. Lymphatic Drainage (HIGH YIELD for cancer staging)

Exam Key: Glottic (true cord) cancers have the best prognosis because of poor lymphatic supply → late metastasis. Supraglottic cancers are often bilateral because of rich bilateral lymphatics.

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10. Phonation and Respiration

• Vocal folds adduct; subglottic air pressure forces them apart momentarily → quasiperiodic vibration → sound column
• Pitch controlled by tension (cricothyroid lengthens/tenses; vocalis relaxes/shortens)
• Rima glottidis is V-shaped; intermembranous part (anterior) closed by LCA; intercartilaginous part (posterior) closed by transverse arytenoid

• Quiet respiration: rima glottidis triangular
• Forced inspiration: PCA contracts → arytenoids rotate laterally → rima glottidis opens wide (rhomboid shape)
• Effort closure: rima glottidis + rima vestibuli both closed (e.g., lifting, coughing, defecation)

• Larynx moves up and forward → epiglottis tilts over laryngeal inlet
• Rima glottidis + rima vestibuli both close
• Laryngeal elevation also opens esophagus (attached to posterior cricoid)

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11. Embryology (Exam Points)

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12. Clinical High-Yield Points

Recurrent Laryngeal Nerve Palsy

• Unilateral RLN injury: Vocal fold on affected side lies in adducted/paramedian position → hoarseness (dysphonia)
• Bilateral RLN injury: Both folds adduct → stridor + respiratory obstruction → may need tracheostomy (bilateral PCA paralyzed; no abduction possible)
• Causes: Thyroid surgery (most common), aortic aneurysm (especially left), mediastinal tumors, lung cancer, neck trauma

Superior Laryngeal Nerve Injury

• External branch injury (during thyroidectomy) → weakness of cricothyroid → loss of voice pitch control, loss of high-pitched singing → common in singers

Cricothyrotomy

• Emergency airway access when obstruction is above the vocal folds (e.g., anaphylaxis, foreign body supraglottis)
• Site: Median cricothyroid ligament, lower third of cricothyroid membrane
• Preferred over tracheotomy in emergencies (faster, more accessible)

Subglottic Stenosis

• Cricoid cartilage = narrowest part of airway in children (not true in adults where glottis is narrowest)
• Prolonged endotracheal intubation in ICU patients → pressure necrosis → subglottic stenosis
• Presents with stridor and respiratory distress

Laryngocele

• Abnormal air-filled dilation of laryngeal saccule
• Internal: Within paralaryngeal fat - may present as airway compromise
• External (mixed): Extends through thyrohyoid membrane → neck swelling (increases with Valsalva)
• Association with glottic tumors causing obstruction of the saccule

Epiglottitis

• H. influenzae type B (children) or Streptococcus (adults)
• "Thumbprint sign" on lateral soft tissue X-ray (thickened epiglottis)
• "Cherry red epiglottis" on laryngoscopy
• NEVER do throat examination in children - can precipitate complete obstruction

Laryngeal Cancer

• Most common site: Glottis (true vocal folds) - 60-65%
• Supraglottis: 30-35%; Subglottis: rare (<5%)
• Glottic: Best prognosis (avascular area, early hoarseness alerts patient, poor lymphatics)
• Supraglottic: Late presentation, bilateral nodal metastasis common
• Risk factors: Smoking + alcohol (synergistic), GERD, voice abuse

Reinke's Space (Reinke's Edema)

• Potential space between the vocal fold epithelium and the vocal ligament
• Edema here (from smoking, voice abuse, hypothyroidism) → Reinke's edema → hoarse low-pitched voice

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13. Quick Summary Table - Nerve to Muscle

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14. Vertebral Level Relations

Exam tip: Cricoid cartilage at C6 = landmark for: (1) Start of trachea, (2) End of pharynx/start of esophagus, (3) Change of common carotid to internal carotid, (4) Inferior thyroid artery entry, (5) Level of cricothyrotomy

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