The larynx (voice box) is an organ located in the anterior neck. It is a component of the respiratory tract, and has several important functions, including phonation, the cough reflex, and protection of the lower respiratory tract.
There are nine cartilages located within the larynx; three unpaired, and six paired. They form the laryngeal skeleton, which provides rigidity and stability. In this article, we shall examine the anatomy of the laryngeal cartilages.
The three unpaired cartilages are the epiglottis, thyroid and cricoid cartilages.
The thyroid cartilage is a large, prominent structure which is easily visible in adult males. It is composed of two sheets (laminae), which join together anteriorly to form the laryngeal prominence (Adam’s apple).
The posterior border of each sheet project superiorly and inferiorly to form the superior and inferior horns (also known as cornu). The superior horns are connected to the hyoid bone via the lateral thyrohyoid ligament, while the inferior horns articulate with the cricoid cartilage.
The cricoid cartilage is a complete ring of hyaline cartilage, consisting of a broad sheet posteriorly and a much narrower arch anteriorly (said to resemble a signet ring in shape).
The cartilage completely encircles the airway, marking the inferior border of the larynx at the level of C6. It articulates with the paired arytenoid cartilages posteriorly, as well as providing an attachment for the inferior horns of the thyroid cartilage.
The cricoid is the only complete circle of cartilage in the larynx or trachea. This is of clinical relevance during emergency intubation – as pressure can be applied to the cricoid to occlude the oesophagus, and thus prevent regurgitation of gastric contents (known as cricoid pressure or Sellick’s manoeuvre).
The epiglottis is a leaf shaped plate of elastic cartilage which marks the entrance to the larynx. Its ‘stalk’ is attached to the back of the anterior aspect of the thyroid cartilage. During swallowing, the epiglottis flattens and moves posteriorly to close off the larynx and prevent aspiration.
There are three paired cartilages – the arytenoid, corniculate and cuneiform. They are situated bilaterally in the larynx.
The arytenoid cartilages are pyramidal shaped structures that sit on the cricoid cartilage. They consist of an apex, base, three sides and two processes, and provides an attachment point for various key structures in the larynx:
- Apex – articulates with the corniculate cartilage.
- Base – articulates with the superior border of the cricoid cartilage.
- Vocal process – provides attachment for the vocal ligament.
- Muscular process – provides attachment for the posterior and lateral cricoarytenoid muscles.
The corniculate cartilages are minor cartilaginous structures. They articulate with the apices of the arytenoid cartilages.
The cuneiform cartilages are located within the ary-epiglottic folds. They have no direct attachment, but act to strengthen the folds.