Nerve supply to vocal cords is by
**Core Concept**
The vocal cords are innervated by both sensory and motor fibers, which are crucial for their function in speech and respiration. The motor innervation is provided by the recurrent laryngeal nerve, a branch of the vagus nerve, while the sensory innervation is provided by the internal laryngeal nerve, also a branch of the vagus nerve.
**Why the Correct Answer is Right**
The recurrent laryngeal nerve supplies motor innervation to all the intrinsic muscles of the larynx, except for the cricothyroid muscle, which is innervated by the external branch of the superior laryngeal nerve. The recurrent laryngeal nerve's motor fibers stimulate the muscles to open and close the glottis, regulating airflow and pitch. The internal laryngeal nerve provides sensory innervation to the mucosa of the larynx, transmitting information related to pain, temperature, and touch.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct nerve responsible for the motor innervation of the vocal cords.
**Option B:** This option is incorrect because it is not a recognized nerve responsible for the innervation of the vocal cords.
**Option C:** This option is incorrect because it is a nerve related to the larynx, but not specifically responsible for the motor innervation of the vocal cords.
**Clinical Pearl / High-Yield Fact**
The recurrent laryngeal nerve is known to be at risk during thyroid and parathyroid surgery due to its close proximity to these glands. Injury to this nerve can result in vocal cord paralysis, which can significantly impact a patient's quality of life.
**Correct Answer: C. Recurrent laryngeal nerve.**