Final answer:
The radial nerve originates from the posterior cord of the brachial plexus, which is comprised of the ventral nerve root axons from spinal roots C5 to T1 and is essential for motor and sensory functions in the upper limb.
Step-by-step explanation:
The radial nerve arises from the ventral nerve root with dorsal roots.
The radial nerve arises from the posterior cord of the brachial plexus, which in turn is composed of fibers from the ventral nerve root axons of spinal roots C5, C6, C7, C8, and T1. The ventral nerve roots contain the axons of motor neurons that originate in the anterior horn of the spinal cord, and these neurons are responsible for sending action potentials to cause skeletal muscles to contract.
The radial nerve, specifically, contains fibers that provide cutaneous sensation in the arm, as well as motor fibers that move muscles in the arm. This nerve plays a crucial role in the motor and sensory functions of the upper limb.