Final answer:
The superior root of the ansa cervicalis is formed by the union of the ventral rami of the first and second cervical spinal nerves (C1 and C2), part of the cervical enlargement region and ventral horn of the spinal cord.
Step-by-step explanation:
The superior root of the ansa cervicalis is a part of the cervical plexus, which is a network of nerve fibers that arise from the cervical enlargement region of the ventral (anterior) horn of the spinal cord. This area has a larger population of neurons that manage the sensory and motor functions of the neck and phrenic nerve, contributing to breathing as it connects with the diaphragm. Specifically, the superior root of the ansa cervicalis is formed by the union of the ventral rami of the first and second cervical spinal nerves (C1 and C2). The Ansa Cervicalis, as a nerve loop, is significant for providing motor innervation to several muscles of the neck.