The thoracic splanchnic nerves are a group of nerves that originate from the thoracic region of the spinal cord. They are part of the autonomic nervous system and primarily carry sympathetic fibers. These nerves play a crucial role in regulating the functions of internal organs, particularly those in the abdominal cavity. There are three main types of thoracic splanchnic nerves: the greater splanchnic nerve, the lesser splanchnic nerve, and the least splanchnic nerve. Each of these nerves innervates specific organs, such as the stomach, liver, and kidneys, helping to control processes like digestion and blood flow.