Which one of the following muscle is functioning as tensor of vocal cord during phonation?
**Core Concept**
The tensor vocis muscle plays a crucial role in modulating the tension of the vocal cords during phonation, allowing for precise control over pitch and volume. This muscle is a small, intrinsic muscle of the larynx. Proper functioning of the tensor vocis muscle is essential for maintaining normal vocal cord mobility and preventing voice disorders.
**Why the Correct Answer is Right**
During phonation, the tensor vocis muscle contracts, pulling the thyroid cartilage anteriorly and increasing the tension of the vocal cords. This muscle is innervated by the external branch of the superior laryngeal nerve, which is responsible for controlling the intrinsic muscles of the larynx. The tensor vocis muscle works in conjunction with the posterior cricoarytenoid muscle to regulate the tension of the vocal cords, allowing for smooth and controlled vocalization.
**Why Each Wrong Option is Incorrect**
**Option A:** The thyroarytenoid muscle is primarily responsible for relaxing the vocal cords, which is the opposite of what the tensor vocis muscle does during phonation.
**Option B:** The cricothyroid muscle is involved in stretching the vocal cords, but it is not the tensor vocis muscle.
**Option C:** The posterior cricoarytenoid muscle is responsible for abducting the vocal cords, which is not related to tension modulation during phonation.
**Clinical Pearl / High-Yield Fact**
The tensor vocis muscle is a key player in maintaining normal vocal cord mobility and preventing voice disorders. Dysfunction of this muscle can lead to conditions such as vocal cord paralysis or spasmodic dysphonia.
**Correct Answer:** C. Cricothyroid muscle.