MCQ – 100775

Correct Answer � A Explanation

The piriform fossa (or piriform recess) is a mucosa-lined depression located on either side of the laryngeal inlet within the laryngopharynx. It is clinically important because it is a common site where foreign bodies (e.g., fish bones) can get lodged.

Nerve Supply:

• The internal laryngeal nerve, a branch of the superior laryngeal nerve, which itself is a branch of the vagus nerve (CN X), provides sensory innervation to the mucosa of the piriform fossa, laryngeal inlet, and upper part of the larynx above the vocal cords.

Clinical relevance:

• Foreign bodies in the piriform fossa can irritate the internal laryngeal nerve and trigger coughing or laryngeal spasm.

• Damage to this nerve (e.g., during surgery like thyroidectomy) can lead to loss of sensation above the vocal cords and aspiration risk.

Reason to rule out other options:

B. Recurrent laryngeal nerve:

• It supplies motor innervation to all intrinsic muscles of the larynx (except cricothyroid) and sensory below the vocal cords.

• It does not supply the piriform fossa, which is above the vocal cords.

C. External laryngeal nerve:

• This is a motor branch to the cricothyroid muscle.

• It has no sensory function, and no role in innervating the piriform fossa.

D. Glossopharyngeal nerve (CN IX):

• Provides sensory innervation to the oropharynx, posterior 1/3 of tongue, palatine tonsils, and upper pharynx, but not the piriform fossa which lies in the laryngopharynx and is served by CN X via the internal laryngeal nerve.