Why vagus nerve is not splanchnic nerve?

The vagus nerve is considered a splanchnic nerve. The splanchnic nerves are nerves that innervate the viscera (organs) of the body, including the abdominal and thoracic cavities. The vagus nerve is one of the longest nerves in the body and innervates many organs in the thoracic and abdominal cavities, including the heart, lungs, stomach, intestines, and liver. It is sometimes referred to as the "wandering nerve" due to its extensive innervation of various structures in the body.

In describing splanchnic nerves, they can be classified further based on their location and distribution:

1. Thoracic Splanchnic Nerves: These nerves arise from the thoracic spinal cord and innervate the organs in the thoracic cavity.

2. Sacral Splanchnic Nerves: These nerves originate from the sacral spinal cord and innervate the organs in the pelvic cavity.

3. Cranial Splanchnic Nerves: These nerves arise from the brain (specifically the brainstem) and innervate organs in the head and neck region, as well as certain thoracic and abdominal organs.

The vagus nerve is a cranial splanchnic nerve, specifically designated as the 10th cranial nerve. It has both somatic and autonomic functions, innervating both skeletal muscles and various organs in the body, including the heart, lungs, and gastrointestinal tract.

Therefore, the vagus nerve is considered a splanchnic nerve, specifically a cranial splanchnic nerve, due to its origin and distribution.