Makindo Medical Notes

Related Subjects: |Anatomy of the Oesophagus |Anatomy of the Diaphragm |Anatomy of Large Bowel |Anatomy of Small Bowel |Anatomy of the Biliary system |Anatomy of the Eye |Anatomy of the Larynx |Anatomy of the Ear |Anatomy of the Pharynx |Anatomy of the Nose |Anatomy of Male Genitalia |Anatomy of Breast |Anatomy of the Stomach |Anatomy of the Rectum |Anatomy of the Spleen

Introduction

The larynx, commonly known as the voice box, is a complex and dynamic organ located in the anterior neck. It functions as a passageway for air between the pharynx and the trachea, produces sounds for speech, and plays a vital role in protecting the lower respiratory tract during swallowing.

Cartilaginous Framework

• Unpaired Cartilages:
  • Thyroid Cartilage: The largest laryngeal cartilage forming the prominent “Adam’s apple,” it provides the main anterior and lateral support.
  • Cricoid Cartilage: A complete, signet ring–shaped cartilage that forms the inferior boundary of the larynx and supports the airway.
  • Epiglottis: A flexible, leaf-shaped cartilage that covers the laryngeal inlet during swallowing to prevent aspiration.
• Paired Cartilages:
  • Arytenoid Cartilages: Pyramid-shaped structures located on the posterior aspect of the cricoid cartilage that control the tension and position of the vocal folds.
  • Corniculate Cartilages: Small horn-shaped cartilages positioned atop the arytenoids, aiding in the fine adjustment of vocal fold movement.
  • Cuneiform Cartilages: Elongated, wedge-shaped cartilages embedded in the aryepiglottic folds that provide structural support to the laryngeal inlet.

Ligaments and Membranes

• Extrinsic Attachments:
  • Thyrohyoid Membrane: Connects the thyroid cartilage to the hyoid bone, stabilizing the upper larynx.
  • Cricotracheal Ligament: Connects the inferior border of the cricoid cartilage to the first tracheal ring, maintaining continuity with the airway.
• Intrinsic Support Structures:
  • Quadrangular Membrane: Extends from the arytenoid cartilages to the epiglottis and forms the upper boundary of the laryngeal ventricle.
  • Cricothyroid Ligament: Connects the cricoid and thyroid cartilages and helps adjust the tension of the vocal folds.

Internal Divisions of the Laryngeal Cavity

• Supraglottis: The region above the true vocal folds, including the epiglottis and vestibular (false) folds.
• Glottis: Contains the true vocal folds and the rima glottidis (the narrow slit between them) responsible for sound production.
• Subglottis: The area below the vocal folds, extending to the inferior border of the cricoid cartilage, where the larynx transitions into the trachea.

Musculature

• Intrinsic Laryngeal Muscles:
  • Cricothyroid Muscle: Tenses and elongates the vocal folds to adjust pitch (innervated by the external branch of the superior laryngeal nerve).
  • Posterior Cricoarytenoid Muscle: The sole abductor of the vocal folds, essential for opening the airway during respiration.
  • Lateral Cricoarytenoid and Interarytenoid Muscles: Adduct the vocal folds, closing the rima glottidis during phonation.
  • Thyroarytenoid (Vocalis) Muscle: Modulates the mass and tension of the vocal folds, influencing sound quality.
• Extrinsic Laryngeal Muscles:
  • These muscles (e.g., thyrohyoid, sternohyoid, and omohyoid) support and position the larynx during swallowing and speech.

Vascular Supply and Innervation

• Blood Supply:
  • Superior Laryngeal Artery: A branch of the superior thyroid artery that supplies the upper larynx.
  • Inferior Laryngeal Artery: Branches from the inferior thyroid artery and supplies the lower laryngeal structures.
• Nerve Supply:
  • Superior Laryngeal Nerve: Splits into an internal branch (sensory to the supraglottis) and an external branch (motor to the cricothyroid muscle).
  • Recurrent Laryngeal Nerve: Provides motor innervation to all intrinsic laryngeal muscles (except the cricothyroid) and sensory innervation to the subglottic region.

Clinical Relevance

• Injury to the recurrent laryngeal nerve can result in vocal cord paralysis, leading to hoarseness or breathing difficulties.
• Inflammatory conditions such as laryngitis can affect vocal quality and cause discomfort.
• The larynx serves as an essential landmark for airway management procedures, such as endotracheal intubation and emergency cricothyrotomy.

Conclusion

The larynx’s intricate anatomy—comprising a robust cartilaginous framework, supportive ligaments and membranes, finely tuned intrinsic muscles, and a dedicated blood and nerve supply—enables it to perform its multifaceted roles in respiration, phonation, and airway protection. A detailed understanding of these structures is crucial for clinical practice and the management of laryngeal disorders.