Which intrinsic laryngeal muscle is responsible for abducting the vocal cords, and which nerve innervates it?

Explanation

## Intrinsic Laryngeal Muscles and Vocal Cord Movement **Key Point:** The posterior cricoarytenoid muscle is the **only muscle that abducts (opens) the vocal cords**, making it the sole abductor of the larynx. All other intrinsic muscles either adduct the cords or modify tension. ## Intrinsic Laryngeal Muscles: Function and Innervation | Muscle | Action | Innervation | Clinical Significance | | --- | --- | --- | --- | | **Posterior cricoarytenoid** | **Abduction (opens cords)** | **RLN** | **Only abductor; bilateral paralysis → airway obstruction** | | Lateral cricoarytenoid | Adduction (closes cords) | RLN | Paired with interarytenoid | | Interarytenoid (transverse & oblique) | Adduction (closes cords) | RLN | Brings arytenoids together | | Thyroarytenoid | Adduction + relaxation | RLN | Shortens vocal cords; internal fibers = vocalis | | Cricothyroid | Tension (elongates cords) | SLN | Only muscle innervated by SLN | **Mnemonic:** **PCA = Only Abductor** — Posterior Cricoarytenoid is the only muscle that Abducts the vocal cords. All others are Adductors or Tensioners. **High-Yield:** Bilateral recurrent laryngeal nerve (RLN) paralysis causes both vocal cords to assume a paramedian position (neither fully open nor fully closed), resulting in **stridor and airway obstruction**. Unilateral RLN paralysis causes hoarseness due to inability to adduct the cord on the affected side. **Clinical Pearl:** The posterior cricoarytenoid is innervated by the RLN, which is why RLN injury causes the vocal cord to rest in a paramedian position — loss of the abductor (posterior cricoarytenoid) combined with unopposed adductors results in cord adduction. [cite:Gray's Anatomy 42e Ch 33; Clinically Oriented Anatomy 8e Ch 8]