Which Laryngeal Cartilage is Composed of Elastic Cartilage?

The laryngeal cartilage that is composed of elastic cartilage is the epiglottis. The epiglottis is a leaf-shaped flap situated beneath the tongue and the hyoid bone, covering the trachea during swallowing to prevent food and liquids from entering the airway.

Overview of the Laryngeal Cartilage Composition

The larynx, which is continuous with the pharynx superiorly and the trachea inferiorly, is comprised of an intricate framework of cartilage held together by fibro-elastic membranes. The intrinsic muscles of the larynx control the movement of these cartilages, allowing vital functions such as protection of the airway, vocalization, and effort closure. The larynx consists of three unpaired cartilages (thyroid, cricoid, and epiglottis) and four pairs of smaller cartilages (arytenoids, corniculates, cuneiforms, and tritiate).

Thyroid Cartilage: The Largest Larynx Cartilage

Thyroid cartilage is the largest cartilage in the larynx, composed of hyaline cartilage. It sits beneath the hyoid bone to which it connects by the thyrohyoid membrane. It articulates inferiorly with the cricoid cartilage. The thyroid cartilage forms a distinctive 'Adam’s apple' in males due to growth during puberty. The cartilage features interlaminar angles, arytenoid horns, and other important anatomical structures which are crucial in vocal cord manipulation and airway protection.

Cricoid Cartilage: A Complete Ring of Hyaline Cartilage

The cricoid cartilage is the only cartilage in the larynx that completely encircles the airway. It has a signet-ring shape, being narrow anteriorly and tall posteriorly. It connects centrally to the thyroid cartilage via the cricothyroid ligament and the conus elasticus. The cricoid cartilage plays a vital role in airway management, as it can be palpitated through the skin and is an important landmark for intubation.

Arytenoid, Corniculate, and Cuneiform Cartilages

The arytenoid, corniculate, and cuneiform cartilages are smaller hyaline cartilages that play a crucial role in vocal cord function. The arytenoid cartilages articulate with the cricoid cartilage and provide attachment points for the vocal cords. The corniculate and cuneiform cartilages, along with the arytenoids, help define the shape of the vocal cords and the laryngeal inlet.

The Epiglottis: Leaf-Shaped and Made of Elastic Cartilage

The epiglottis is the only laryngeal cartilage composed of elastic cartilage. It has a leaf-like shape with a stem arising from the thyroid cartilage and a broadened upper edge that can cover the laryngeal inlet during swallowing. The epiglottis plays a critical role in airway protection, though its exact function in adults is still a topic of debate. Pathological conditions such as acute epiglottitis and laryngomalacia highlight the potential for airway compromise.

Embryology and Anatomical Development

Laryngeal cartilage development begins in the fourth week of embryogenesis. Recent studies, such as the 2018 study on human embryos, have provided new insights into the embryology of the hyoid-larynx complex. The thyroid and cricoid cartilages arise from mesenchymal condensations in the neck regions, differing from previous descriptions based on fourth and sixth pharyngeal arch cartilages.

Blood Supply and Nerve Supply

Laryngeal cartilages are avascular and derive nutrition through diffusion from the blood supply of the overlying mucosa and surrounding tissue. The superior thyroid branch of the external carotid artery is the primary blood source. Unlike the laryngeal cartilages, the intrinsic muscles of the larynx have a rich nerve supply, necessitating detailed knowledge for surgical procedures.

Clinical Significance

Understanding the anatomy of the laryngeal cartilages is crucial for medical practitioners. Pediatricians must be aware of conditions such as epiglottitis and croup. Surgeons, anesthetists, and emergency physicians requiring airway access need to know the surface anatomy of the thyroid and cricoid cartilages for proper airway management. Otolaryngologists must have an intimate knowledge of these cartilages as landmarks during surgery and sites of cancer invasion, significantly impacting prognosis and management.

In conclusion, while the cricoid and thyroid cartilages consist of hyaline cartilage, the epiglottis is the only laryngeal cartilage composed of elastic cartilage, providing unique shape and function in the larynx.