Final answer:
The two upper motor neuron pathways involved in the movement of distal segments are the corticospinal and rubrospinal tracts, with the corticospinal tract being the primary pathway for controlling voluntary, skilled movements of the limbs.
Step-by-step explanation:
The two upper motor neuron (UMN) pathways involved in the movement of distal segments are the corticospinal and rubrospinal tracts. The corticospinal tract is the major descending tract that controls skeletal muscle movements. It originates in the primary motor cortex and synapses on lower motor neurons (LMN), which in turn project to the skeletal muscles. The rubrospinal tract also plays a role in motor control but to a lesser degree. The corticospinal tract is largely responsible for moving the muscles of the arms and legs, while also aiding in precise, skilled, voluntary movements. Conversely, the vestibulospinal and reticulospinal tracts are more involved in posture and locomotion, not specifically the fine-tuned movement of distal segments.