Which nerve provides the majority of parasympathetic innervation to the thorax and abdomen?

• A. Vagus nerve (CN X)
• B. Oculomotor nerve (CN III)
• C. Glossopharyngeal nerve (CN IX)
• D. Hypoglossal nerve (CN XII)

Answer: (A)

Parasympathetic innervation to the thorax and most of the abdomen is provided primarily by the vagus nerve. It carries preganglionic parasympathetic fibers from the brainstem that reach the heart, lungs, and esophagus in the chest, then extend to the stomach, liver, pancreas, and much of the intestine in the abdomen, up to the proximal two-thirds of the transverse colon. The distal colon and pelvic organs receive parasympathetic input from the pelvic splanchnic nerves (S2–S4). Other nerves listed aren’t responsible for this broad thoracic and abdominal parasympathetic supply: the oculomotor nerve innervates the eye’s pupil and lens; the glossopharyngeal nerve targets the parotid gland; the hypoglossal nerve is motor to the tongue.