Which of the following laryngeal muscles constitute tensors of vocal cord?

Okay, let's tackle this question about the laryngeal muscles that act as tensors of the vocal cords. First, I need to recall the anatomy of the larynx and the functions of its muscles. The larynx has several muscles that control the vocal cords, and their primary functions are to tense or relax them, as well as to open or close the glottis.

The question is asking specifically about the tensor muscles. Tensor muscles would be those that stretch or tighten the vocal cords, increasing their tension. I remember that the cricothyroid muscle is one of the main tensors. It does this by rotating the thyroid cartilage forward relative to the cricoid cartilage, which elongates and tightens the vocal cords. Another muscle might be the thyroarytenoid, but wait, I think the thyroarytenoid is more of a relaxer because it shortens the vocal cords. The posterior cricoarytenoid muscles are involved in abduction, opening the glottis, so they probably don't tense the cords. The lateral cricoarytenoid adducts the cords, closing the glottis, but again, not necessarily tensing them.

So the correct answer should be the cricothyroid muscle. Let me check the options again. If the options are A to D, and the correct one is C, then the explanation would need to detail why cricothyroid is the tensor. The other options would be incorrect because they either relax the cords or have different functions. The clinical pearl here is that the cricothyroid is the primary tensor, and it's innervated by the external branch of the superior laryngeal nerve, which is important for voice production. Students often confuse the functions of thyroarytenoid and cricothyroid, so emphasizing that the thyroarytenoid is a relaxer is key.

**Core Concept**
The laryngeal muscles that act as tensors of the vocal cords are responsible for elongating and tightening the vocal folds to increase pitch and vocal intensity. The **cricothyroid muscle** is the primary tensor, while others like the thyroarytenoid function as relaxers.

**Why the Correct Answer is Right**
The **cricothyroid muscle** tenses the vocal cords by rotating the thyroid cartilage anteriorly relative to the cricoid cartilage. This elongates and tightens the vocal ligaments, increasing vocal pitch. It is innervated by the external branch of the superior laryngeal nerve (a branch of the vagus nerve), distinguishing it from intrinsic laryngeal muscles innervated by the recurrent laryngeal nerve.

**Why Each Wrong Option is Incorrect**
**Option A:** The thyroarytenoid muscle (and its internal part, the vocalis) *relaxes* the vocal cords by shortening them, opposite to tensor function.
**Option B:** The posterior cricoarytenoid muscle is an *abductor* of the vocal cords, opening the glottis during inhalation.
**Option D:** The lateral cricoarytenoid muscle *adducts* the vocal cords, closing the glottis, but does not significantly alter their tension.

**Clinical Pearl / High-Yield Fact**
The cricothyroid muscle is unique among laryngeal muscles for its tensor role and

✓ Correct Answer: D. Cricothyroid and internal thyroarytenoid