Tensor tympani is supplied by branch from the medial pterygoid nerve which is a direct branch of mandibular division of trigeminal nerve (and not posterior division of mandibular nerve).
Tensor Tympani Muscle:
-Tensor tympani develops from the first arch.
-Arises from the semicanal for tensor tympani in the anterior wall of middle ear.
-Hooks around the processus cochleariformis in the medial wall
-Attaches the neck of malleus in the lateral wall.
-Action is to medialize the malleus & conduct sound.
Note:
-The posterior division of mandibular nerve is mainly sensory and divides into three branches.
-The auriculotemporal nerve.
-The lingual nerve.
-The inferior alveolar (dental) nerve.
-The motor component of posterior division of mandibular nerve supplies the mylohyoid and anterior belly of digastric.