MEDICAL PHYSIOLOGY

Detailed explanation-1: -The external laryngeal branch travels to the inferior pharyngeal constrictor muscle. This branch innervates an intrinsic laryngeal muscle called the cricothyroid muscle.

Detailed explanation-2: -The superior laryngeal branch of the vagus nerve originates from the 4th pharyngeal arch along with the cricothyroid muscle. This developmental pattern elucidates why the cricothyroid muscle is the only muscle that receives innervation via the superior laryngeal nerve.

Detailed explanation-3: -Functions. The vagus nerve has a very extensive distribution. Sensory: Innervates the skin of the external acoustic meatus and the internal surfaces of the laryngopharynx and larynx. Provides visceral sensation to the heart and abdominal viscera.

Detailed explanation-4: -The classical understanding of the anatomy is that the cricothyroid muscle (CTM) is innervated solely by the external branch of the superior laryngeal nerve (EBSLN), and the endolaryngeal muscles are covered only by the recurrent laryngeal nerve (RLN).

Detailed explanation-5: -Inferior laryngeal branch of the recurrent laryngeal nerve: excluding the cricothyroid muscle [innervated by the superior laryngeal nerve], the inferior laryngeal branch of the recurrent laryngeal nerve innervates all intrinsic muscles of the larynx.