Final answer:
The anterior spinal artery supplies the ventral/anterior nerve rootlet, originating from the vertebral arteries and running along the anterior surface of the spinal cord.
Step-by-step explanation:
The vessel that supplies the ventral/anterior nerve rootlet is the anterior spinal artery. This artery is a blood vessel that originates from the merged branches of the vertebral arteries. It runs along the anterior median fissure, on the anterior surface of the spinal cord, delivering the necessary blood supply to that region. The ventral nerve rootlets contain axons emerging from the anterior or lateral horns of the spinal cord, carrying motor signals out to the body.