Describe the anatomy of the larynx.

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College Answer

For this question, candidates were expected to address the location of the larynx, its relations, the cartilages (single and paired), ligaments, muscles (intrinsic and extrinsic), innervation (sensory and muscular) and blood supply (including venous drainage). Marks were apportioned to each section, so whilst some detail was required, breadth of knowledge was also important. Most candidates had a grasp of the gross anatomy, the main relations and at least the innervation provided by the recurrent laryngeal nerve. However, an understanding of the functional anatomy of the cartilages was not always apparent. It should be noted that not every single muscle needed to be named (especially for the extrinsic muscles), but an understanding of the major muscle groups should have been included.

Discussion

  • Landmarks:
    • Laryngeal prominence ("Adam's apple")
  • Basic structural anatomy: 
    • Considered part of the respiratory tract
    • Lined by pseudostratified columnar ciliated epithelium
    • Divides the airways into "upper" and "lower"
  • Relations: 
    • Superiorly: bounded by the hyoid bone
    • Anteriorly, covered by skin and protected by the thyroid cartilage
    • Inferiorly: becomes continuous with the trachea at the level of C6
    • Posteriorly: projects into the laryngopharynx
    • Laryngeal inlet:
      • Faces backwards and upwards
      • Bounded anteriorly by the upper edge of the epiglottis,
      • Bounded laterally and postriorly by the aryepiglottic folds
      • Bounded posteriorly by the interarytenoid fissure
    • Divided by the vocal folds into upper and lower half
  • Blood supply: ​​​​​
    • Upper half: superior laryngeal branch of the superior thyroid artery
    • Lower half: inferior laryngeal branch of the inferior thyroid artery
  • Venous drainage:
    • Upper half: superior laryngeal veins which empty into the superior thyroid veins
    • Lower half:inferior laryngeal veins to the inferior thyroid veins, which drain into the brachiocephalic veins
  • Lymphatic drainage:
    • upper and lower groups of deep cervical nodes
  • Cartilages:
    • Paired: arytenoid, corniculate and cuneiform​​​​​​​
    • Unpaired: epiglottis, thyroid and cricoid​​​​​​​
  • Ligaments:
    • ​​​​​​​Intrinsic:  cricothyroid ligament and quadrangular membrane
    • Extrinsic: thyrohyoid membrane, median and lateral thyrohyoid ligament, hyo-epiglottic ligament, cricotracheal ligament.
  • Muscles:
    • ​​​​​​​Intrinsic: cricothyroid, thyroarytenoid, posterior cricoarytenoid, lateral cricoarytenoid, transverse and oblique arytenoids. 
    • Extrinsic: supra and infrahyoid group of muscles: digastric, mylohyoid, stylohyoid, omohyoid, thyrohyoid. Also sternohyoid and sternothyroid.
  • Innervation: 
    • All the muscles of the larynx are supplied by the recurrent laryngeal nerve except cricothyroid which is innervated on its external surface by the external laryngeal nerve.
  • Function
    • Respiration (conductive airway)
    • Swallowing
    • Phonation
    • Cough reflex

References

Mete, Aslı, and İlknur Hatice Akbudak. "Functional Anatomy and Physiology of Airway." Tracheal Intubation. IntechOpen, 2018.

Marchant, Warwick. "Anatomy of the larynx, trachea and bronchi." Anaesthesia & intensive care medicine 6.8 (2005): 253-255.