Motor innervation to the posterior belly of the digastric muscle is supplied by_______________?
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Answer: A. Facial nerve
Explanation
The posterior belly of the digastric muscle originates from the second pharyngeal arch and is innervated by the facial nerve. Cranial nerve VII sends a dedicated motor branch to the posterior belly as it emerges from the stylomastoid foramen. This second arch embryological origin explains why its motor supply comes from the facial nerve. The digastric muscle features two bellies sharing an intermediate tendon attached to the hyoid bone. The posterior belly acts to elevate and pull the hyoid bone posteriorly during swallowing. Pharyngeal arch development dictates that adjacent muscles share common cranial nerve motor supplies.
The vagus nerve innervates laryngeal and pharyngeal structures without supplying the digastric muscle bellies. The mylohyoid nerve is a branch of the trigeminal nerve that innervates the anterior belly of the digastric. The inferior alveolar nerve provides sensory innervation to mandibular teeth and bone rather than neck muscles.
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