Final answer:
The larynx and pharynx are innervated by the internal and external divisions of the superior laryngeal nerve for sensory and motor functions, respectively, and by the recurrent laryngeal nerve for motor functions and some sensory innervation. The pharynx has three parts: nasopharynx, oropharynx, and laryngopharynx, pertaining to both the digestive and respiratory pathways.
Step-by-step explanation:
The sensory and motor innervation of the larynx and pharynx includes several nerves and their specific divisions. The superior laryngeal nerve, which branches from the vagus nerve (cranial nerve X), has an internal division and an external division, serving different functions:
- Superior laryngeal nerve - internal division: This division provides sensory innervation to the mucosa above the vocal cords, including the larynx.
- Superior laryngeal nerve - external division: The external branch of the superior laryngeal nerve is primarily a motor nerve that innervates the cricothyroid muscle, which plays a critical role in tension and pitch modulation of the vocal cords.
- Recurrent laryngeal nerve: This nerve provides motor innervation to most of the intrinsic muscles of the larynx, which are responsible for phonation and protecting the airway during swallowing. It also provides sensory innervation to the mucosa below the vocal cords.
The pharynx is split into three parts: the nasopharynx, which is involved in breathing and speech, the oropharynx and laryngopharynx which serve both respiration and digestion. The laryngopharynx continues the route of ingested material and air, leading anteriorly to the larynx and posteriorly to the esophagus.
The sensory division of the peripheral nervous system interprets messages from sense organs and internal organs, whereas the motor division sends messages to internal organs, glands, and muscles. The larynx and pharynx receive their sensory and motor innervation mainly through branches of the vagus nerve.