Which nerve is responsible for the innervation of the posterior belly of the digastric muscle?

The correct answer is the facial nerve, which is responsible for the innervation of the posterior belly of the digastric muscle. The digastric muscle consists of two muscle bellies: the anterior belly, innervated by the mandibular branch of the trigeminal nerve, and the posterior belly, innervated by the facial nerve. Specifically, the facial nerve, through its branch called the digastric branch, provides motor innervation to the posterior belly, allowing for its contraction and involvement in actions such as depression of the mandible and stabilization of the hyoid bone during swallowing.

The other options do not provide the correct innervation: the trigeminal nerve is primarily responsible for sensory and motor functions in the face, particularly for the anterior belly of the digastric muscle; the hypoglossal nerve innervates the muscles of the tongue; while the vagus nerve is involved in autonomic functions and innervates various muscles involved in the throat and voice production but does not innervate the digastric muscle. Understanding the specific innervation patterns is essential for the comprehension of muscle function and actions in surgical contexts.