Answer
Fig. 15.7
Vagus nerve (CN X).
Work Step by Step
The vagus nerve carries 90% of the parasympathetic preganglionic fibers. It travels down the neck and through the thorax ; at its lower end it penetrates the diaphragm and enters the abdominal cavity. In the thorax the vagus gives rise to a cardiac plexus-- with fibers going to the heart; a pulmonary plexus-- with fibers that follow bronchi and blood vessels into the lungs, and an esophageal plexus that controls swallowing.