Which intrinsic laryngeal muscle is responsible for abduction of the vocal cords and is innervated by the recurrent laryngeal nerve?

Explanation

## Intrinsic Laryngeal Muscles: Abduction Function **Key Point:** The posterior cricoarytenoid is the ONLY intrinsic laryngeal muscle that abducts (separates) the vocal cords, and it is innervated by the recurrent laryngeal nerve. ### Anatomical Basis **High-Yield:** Posterior cricoarytenoid muscle: - **Origin:** Posterior surface of cricoid cartilage - **Insertion:** Muscular process of arytenoid cartilage - **Action:** Rotates arytenoid cartilage laterally → abducts vocal cords - **Innervation:** Recurrent laryngeal nerve (RLN) - **Bilateral action:** Opens the rima glottidis (airway opening) ### Clinical Significance **Clinical Pearl:** Bilateral recurrent laryngeal nerve injury results in: - Both vocal cords in paramedian position (abduction lost) - Severe airway obstruction - Stridor and dyspnea - Tracheostomy may be required ### Intrinsic Muscle Classification Table | Muscle | Action | Innervation | Clinical Importance | |--------|--------|-------------|---------------------| | Posterior cricoarytenoid | Abduction | RLN | Only abductor; airway opening | | Lateral cricoarytenoid | Adduction | RLN | Vocal cord closure | | Interarytenoid | Adduction | RLN | Vocal cord approximation | | Thyroarytenoid | Adduction, tension | RLN | Phonation, pitch control | | Cricothyroid | Tension | Superior laryngeal nerve | Pitch elevation | **Mnemonic:** **LACTIC** = Lateral cricoarytenoid, Adduction, Thyroarytenoid, Interarytenoid, Cricothyroid, Innervation (RLN for all except cricothyroid) ### Functional Significance **Warning:** Loss of posterior cricoarytenoid function (RLN palsy) is more dangerous than loss of adductors because it eliminates the only abductor muscle, leading to airway compromise rather than just voice changes.