Final answer:
The white rami communicantes could be the damaged structures preventing a visceral signal from the small intestine reaching the spinal cord, as they carry the preganglionic sympathetic fibers towards the spinal nerve.
Step-by-step explanation:
If the visceral signal from the small intestine does not reach the spinal cord, the affected structures might be the white rami communicantes. This is because the white rami communicantes are myelinated structures that provide a short connection from a sympathetic chain ganglion to the spinal nerve that contains the preganglionic sympathetic fiber. Preganglionic neurons that originate in the spinal cord pass through the white rami communicantes and then can continue through splanchnic nerves to synapse within a prevertebral ganglion, like the celiac or the inferior mesenteric ganglion, rather than synapsing in the sympathetic chain ganglia. This route is typically taken by fibers that innervate the abdominal and pelvic organs. The gray rami communicantes, on the other hand, contain postganglionic fibers. Thus, if a visceral signal is not reaching the spinal cord, the white rami communicantes are a possible site of damage, impacting the preganglionic sympathetic fibers that should reach the spinal cord.