12 most Solved Questions on Laryngeal Nerve Supply

NERVE SUPPLY OF LARYNX

Nerve supply of larynx

  • Sensory:
    • The internal laryngeal nerve supplies the mucous membrane above the level of the vocal folds.
    • The recurrent laryngeal nerve supplies the mucosa of the vocal cord and the subglottis(below the level of the vocal folds).
  • Motor:
    • All intrinsic muscles of the larynx are supplied by the recurrent laryngeal nerve except for the cricothyroid which is supplied by the external laryngeal nerve.

SUPERIOR LARYNGEAL NERVE

  • Arises from inferior ganglion of the vagus descends behind the internal carotid artery and at the level of greater cornua of hyoid bone, divides into external and internal branches.
  • The internal branch pierces the thyrohyoid membrane and supplies sensory innervation to the larynx (above the level of the vocal folds.) and hypopharynx.
  • The external laryngeal nerve  lies in relation to superior thyroid artery and supplies Cricothyroid.
  • External Laryngeal Nerve is the most common nerve injured in ligation of superior thyroid artery.
  • The cricothyroid muscle functions to increase tension in the vocal folds, especially at the upper range of pitch or loudness.
RECURRENT LARYNGEAL NERVE
  • Arises from the Vagus, travels further on the left where it loops around the arch of Aorta while on the right, it travels around the subclavian artery.
  • Left recurrent Laryngeal nerve is injured more frquently because of its longer and more extensive course.
  • The RLN is often in close proximity to Berry’s ligament.
  • The distal end of the RLN was identified along the tracheoesophageal groove.
  • The most common angle that the RLN forms with the tracheoesophageal groove is 15-30 degree.
  • When enlarged, tubercle of Zuckerkandl is a consistent landmark for the RLN because the nerve almost always courses medial and deep to it.
  • Rarely (0.5% to 1% of individuals), in presence of aberrant right subclavian artery, arising from the aorta after the left subclavian artery has given off, the right RLN passes directly from the vagus nerve in the neck towards the larynx and does not recur around subclavian artery. This uncommon anatomic variation of the RLN makes it highly susceptible to surgical injury and is known as right “nonrecurrent” laryngeal nerve.
  • The recurrent laryngeal nerve lies close to inferior thyroid artery.
  • Its motor branch supplies all the intinsic muscles of the larynx(Lateral cricoarytenoid, posterior cricorytenoid, transverse and oblique interarytenoid and thyroarytenoid) except Cricothyroid.
  • Sensory branch supplies the mucosa of the vocal cord and the subglottis(below the level of the vocal folds).
  • The muscle fibers of the trachea are innervated by the recurrent laryngeal nerve, which also carry sensory fibers from the mucous membrane.
    Recurrent laryngeal branches of the vagus nerve supply the striated muscle in the upper third of the esophagus
  •  The intrinsic muscles of the larynx, all of which are innervated by the recurrent laryngeal nerve, include the:
    • Posterior cricoarytenoid the only abductor of the vocal folds. Functions to open the glottis by rotary motion on the arytenoid cartilages. Also tenses cords during phonation.
    • Lateral cricoarytenoid functions to close glottis by rotating arytenoids medially.
    • Transverse arytenoid only unpaired muscle of the larynx. Functions to approximate bodies of arytenoids closing posterior aspect of glottis.
    • Oblique arytenoid this muscle plus action of transverse arytenoid function to close laryngeal introitus during swallowing.
    • Thyroarytenoid – very broad muscle, usually divided into three parts:
      • Thyroarytenoideus internus (vocalis) – adductor and major tensor of free edge of vocal fold.
      • Thyroarytenoideus externus – major adductor of vocal fold
      • Thyroepiglotticus – shortens vocal ligaments

IMPORTANT ANATOMOSIS BETWEEN LARYNGEAL NERVES

There are two types of important anastmosis between laryngeal branches of vagus :

1) Galen anastomosis (Ramus anastomoticus or Ansa of Galen)

This is an anastomosis between the recurrent laryngeal nerve and internal laryngeal nerve (internal branch of superior laryngeal nerve).

Generally, posterior branch of recurrent laryngeal nerve contributes to the anastomosis; however, anterior branch can also contribute.

2) Human communicating nerve

It is an anastomosis between recurrent laryngeal nerve (distal part) and external laryngeal nerve (external branch of superior laryngeal nerve).

Exam Question of

  • Cricothyroid muscle is supplied by external laryngeal nerve.
  • The nerve supply of the muscles:Lateral cricoarytenoid ,Posterior cricoarytenoid ,Thyroepiglotticus is by Recurrent laryngeal nerve.
  • Nerve supply of the mucosa of larynx is by Internal and recurrent laryngeal nerve.
  • Recurrent laryngeal nerve is in close association with Inferior thyroid artery.
  • External Laryngeal Nerve is the most common nerve injured in ligation of superior thyroid artery.
  • Galen’s anastomosis is between Recurrent laryngeal nerve and internal laryngeal nerve.

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Laryngeal Nerve Supply

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