Question 16

College Answer

This question required candidates to address the following relevant to the anatomy of the larynx - it's location and extent; relations; structure (paired and unpaired cartilages; major ligaments; intrinsic and extrinsic muscles); nerve supply (sensory and motor); and blood supply (and venous darinage). There were some marks allocated for other correct information relevant to the anatomy of the larynx (e.g. epithelium; differences in age; lymphatic drainage). This was a purely anatomy question so functions of the larynx was not required.

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.

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

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