- Primary Function: Main parasympathetic (“rest and digest”) innervation to thorax and abdomen up to the splenic flexure.
- Key Anatomy:
- Exits skull via jugular foramen.
- Brainstem Nuclei:
- Nucleus Ambiguus: Motor to larynx/pharynx (swallowing, phonation).
- Dorsal Motor Nucleus: Parasympathetics to heart, lungs, GI.
- Nucleus Solitarius: Visceral sensory (taste, baroreceptors).
- Major Branches & Clinical Correlates:
- Recurrent Laryngeal Nerve (RLN)
- Function: Motor to most intrinsic laryngeal muscles.
- Lesion: Hoarseness.
- Vulnerable during: Thyroid surgery.
- Course: Left RLN loops under aortic arch; Right RLN loops under right subclavian artery.
- Superior Laryngeal Nerve (SLN)
- Function: External branch innervates cricothyroid muscle (creates high-pitched sounds).
- Lesion: Monotonous voice.
- Vulnerable during: Ligation of superior thyroid artery in thyroidectomy.
- Vagal Trunk Lesion (e.g., at jugular foramen):
- Hoarseness (laryngeal muscle paralysis).
- Dysphagia (pharyngeal muscle paralysis).
- Uvula deviates AWAY from the side of the lesion.
- Reflexes:
- Gag Reflex: Afferent = CN IX, Efferent = CN X.
- Baroreceptor Reflex: Aortic arch afferent and all parasympathetic efferent signals are carried by CN X.