Larynx and vocal apparatus

Larynx and vocal apparatus

Larynx and vocal apparatus

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Laryngeal Skeleton - Framework of Voice

Larynx and associated neurovasculature

Framework composed of nine cartilages connected by membranes and ligaments, providing structure and enabling phonation.

  • Unpaired Cartilages (3)
    • Thyroid: Largest, forms laryngeal prominence (Adam's apple).
    • Cricoid: Complete ring, signet-shaped. Landmark for cricothyrotomy.
    • Epiglottis: Elastic cartilage; covers laryngeal inlet during swallowing.
  • Paired Cartilages (3x2)
    • Arytenoid: Pyramidal; anchors vocal ligaments.
    • Corniculate: Sit atop arytenoids.
    • Cuneiform: Within aryepiglottic folds.

⭐ The cricoid cartilage is the only complete cartilaginous ring in the airway. Its posterior lamina is broad, and the anterior arch is narrow, creating a signet ring shape. This integrity is vital for maintaining airway patency.

Laryngeal Muscles - The Larynx's Puppeteers

  • Intrinsic Muscles: Fine-tune vocal cord movement. All are innervated by the Recurrent Laryngeal Nerve (RLN) except the cricothyroid.
    • Tensors:
      • Cricothyroid: Tenses cords (↑ pitch). Innervated by the Superior Laryngeal Nerve (external branch).
      • Thyroarytenoid (Vocalis): Relaxes cords (↓ pitch).
    • Adductors (close cords):
      • Lateral Cricoarytenoid
      • Transverse Arytenoid
    • Abductor (opens cords):
      • Posterior Cricoarytenoid

Superior view of intrinsic laryngeal muscles

⭐ The Posterior Cricoarytenoid (PCA) is the sole abductor of the vocal cords. Bilateral paralysis can cause acute airway obstruction, as it prevents breathing.

Innervation & Vasculature - Laryngeal Lifelines

  • Innervation (Vagus Nerve, CN X):

    • Superior Laryngeal N. (SLN):
      • Internal branch: Sensory mucosa above vocal cords.
      • External branch: Motor to cricothyroid (tenses cords, ↑ pitch).
    • Recurrent Laryngeal N. (RLN):
      • Motor to all other intrinsic muscles (phonation, respiration).
      • Sensory mucosa below vocal cords.
      • 📌 Mnemonic: Cricothyroid is the Chief Tensor, supplied by the eXternal branch of X (SLN).
  • Vasculature: Arteries travel with corresponding nerves.

    • Superior Laryngeal Artery (from Sup. Thyroid a.)
    • Inferior Laryngeal Artery (from Inf. Thyroid a.)

Laryngeal Nerves and Blood Supply

⭐ The left RLN has a longer course, looping under the aortic arch, making it more susceptible to injury from thoracic conditions (e.g., aortic aneurysm, lung cancer), causing hoarseness.

Clinical Correlates - When Things Go Wrong

  • Vocal Cord Paralysis:
    • Cause: Injury to the Recurrent Laryngeal Nerve (RLN) is the most common cause.
    • Etiology: Thyroid surgery, aortic arch pathology (left RLN), Pancoast tumor.
    • Symptoms: Hoarseness, dysphonia, and risk of aspiration.
  • Laryngitis:
    • Inflammation of the larynx, typically from viral infections or vocal overuse.
  • Laryngeal Carcinoma:
    • Strongly associated with smoking and alcohol (synergistic effect).
    • Presents with persistent hoarseness, dysphagia, and weight loss.
    • Most common type is squamous cell carcinoma.

Ortner's Syndrome: Cardiovocal syndrome where a large left atrium or aortic arch aneurysm compresses the left recurrent laryngeal nerve, causing hoarseness.

Recurrent laryngeal nerve course and vulnerability points

High‑Yield Points - ⚡ Biggest Takeaways

  • The recurrent laryngeal nerve (RLN) innervates all intrinsic laryngeal muscles except the cricothyroid. Unilateral damage causes hoarseness.
  • The cricothyroid muscle, innervated by the external branch of the superior laryngeal nerve, tenses the vocal cords to control pitch.
  • The posterior cricoarytenoid (PCA) is the sole abductor of the vocal cords; bilateral paralysis can cause airway obstruction.
  • Internal branch of the superior laryngeal nerve provides sensation to the supraglottis; injury leads to aspiration risk.
  • Cricothyrotomy is performed through the cricothyroid membrane.

Practice Questions: Larynx and vocal apparatus

Test your understanding with these related questions

A 45-year-old man presents to an urgent care clinic because he coughed up blood this morning. Although he had a persistent cough for the past 3 weeks, he had never coughed up blood until now. His voice is hoarse and admits that it has been like that for the past few months. Both his past medical history and family history are insignificant. He has smoked a pack of cigarettes a day since the age of 20 and drinks wine every night before bed. His vitals are: heart rate of 78/min, respiratory rate of 14/min, temperature of 36.5°C (97.8°F), blood pressure of 140/88 mm Hg. An indirect laryngoscopy reveals a rough vegetating lesion on the free border of the right vocal cord. Which of the following is the most likely diagnosis?

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Flashcards: Larynx and vocal apparatus

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The _____ muscle is responsible for dampening of loud noises.

TAP TO REVEAL ANSWER

The _____ muscle is responsible for dampening of loud noises.

tensor tympani

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