Regarding the intrinsic muscles of the larynx, all of the following statements are correct EXCEPT:

Explanation

## Intrinsic Laryngeal Muscles: Function and Innervation ### Overview The five intrinsic muscles of the larynx control vocal cord position and tension. Their innervation pattern is a classic NEET PG high-yield topic. ### Intrinsic Muscles: Function and Innervation Table | Muscle | Action | Innervation | Key Feature | |--------|--------|-------------|-------------| | **Posterior cricoarytenoid** | Abduction (opens cords) | RLN | **Only abductor** | | **Lateral cricoarytenoid** | Adduction (closes cords) | RLN | Paired muscle | | **Interarytenoid (transverse & oblique)** | Adduction (closes cords) | RLN | Unpaired/paired variants | | **Thyroarytenoid** | Relaxes/shortens cords | RLN | Includes vocalis | | **Cricothyroid** | Tenses cords | **SLN (external branch)** | Only muscle NOT innervated by RLN | ### Analysis of Each Option **Option 1 (Correct):** The posterior cricoarytenoid is the **only abductor** of the vocal cords and is innervated by the recurrent laryngeal nerve (RLN). This is critical because bilateral RLN injury causes vocal cord paralysis in adduction (stridor). ✓ **Option 2 (INCORRECT):** The lateral cricoarytenoid muscle is innervated by the **recurrent laryngeal nerve (RLN)**, NOT the superior laryngeal nerve (SLN). The SLN innervates only the cricothyroid muscle. ✗ **Option 3 (Correct):** The interarytenoid muscles (both transverse and oblique components) adduct the vocal cords and are innervated by the RLN. ✓ **Option 4 (Correct):** The thyroarytenoid muscle relaxes and shortens the vocal cords (opposite of cricothyroid) and is innervated by the RLN. ✓ ### Mnemonic: **"LATTE"** — **L**ateral cricoarytenoid, **A**rytenoid (interarytenoid), **T**hyroarytenoid, **T**ransverse/oblique, **E**very one innervated by RLN (except cricothyroid). All adductors/relaxers use RLN. ### High-Yield: **SLN innervates ONLY the cricothyroid muscle** (tenses cords via external branch). All other intrinsic muscles use RLN. This distinction is tested in every NEET PG exam cycle. ### Clinical Pearl: Bilateral RLN injury → vocal cords stuck in **midline (adducted) position** → stridor and airway obstruction. Bilateral SLN injury → loss of pitch control and vocal fatigue (cords cannot be tensed).