Final answer:
The arms are supplied by the brachial plexus, encompassing spinal nerves C4 to T1, and the legs by the lumbar and sacral plexuses, with the lumbar plexus servicing the anterior leg and sacral plexus the posterior leg.
Step-by-step explanation:
The plexus that supplies the arms is known as the brachial plexus, while the one that supplies the legs can be divided into two: the lumbar plexus, which supplies nerves to the anterior leg, and the sacral plexus, which supplies the posterior leg. The brachial plexus derives from spinal nerves C4 through T1 and includes major nerves like the radial, ulnar, and median nerves that facilitate both sensory and motor functions in the arms.
Meanwhile, the lumbar plexus originates from all lumbar spinal nerves and includes the femoral nerve, among others, mainly enervating the anterior aspect of the leg. The sacral plexus is formed from spinal nerves L4 to S4 and gives rise to the sciatic nerve, a combination of the tibial nerve and the fibular nerve, which serves the posterior leg.