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(nervus accessorius, or nerve of Willis, after the English physician T. Willis, who first described it in 1664), the 11th pair of cranial nerves.
The accessory nerve originates in the medulla oblongata and the spinal cord. It emerges from the cranial cavity with the glossopharyngeal and vagus nerves through the jugular foramen and supplies motor fibers to the sternocleidomastoid muscle on the neck (with unilateral contraction, this muscle inclines the head to the side and turns the face in the opposite direction) and to the trapezius muscle on the back (it raises the pectoral girdle and adducts the scapula). Some of the fibers of the accessory nerve are connected to the vagus nerve and with its branches reach the muscles of the soft palate, the pharynx, and the larynx.