Cuneiform cartilages

The cuneiform cartilages are small, paired, rod-shaped structures made of elastic cartilage located within the larynx. They are considered accessory cartilages of the larynx and provide structural support to the soft tissues surrounding the laryngeal inlet. Although small and less prominent than other laryngeal cartilages, they play a role in maintaining the structure of the larynx.

Location

The cuneiform cartilages are embedded within the aryepiglottic folds, which extend from the arytenoid cartilages to the sides of the epiglottis. They are located superior and slightly anterior to the corniculate cartilages and are positioned lateral to the arytenoid cartilages in the posterior aspect of the larynx.

Structure and Anatomy

The cuneiform cartilages are small, paired structures that form part of the supportive framework of the larynx. Despite their small size, they contribute to the stability and function of the laryngeal tissues. Below is a detailed description of their anatomy.

Shape and Structure

• The cuneiform cartilages are small, rod-shaped structures made of elastic cartilage. This elastic cartilage allows the cuneiform cartilages to provide flexible support to the surrounding soft tissues, such as the aryepiglottic folds.
• Their cylindrical or wedge-like appearance gives them their name, with “cuneiform” derived from the Latin word “cuneus,” meaning wedge. They are relatively tiny compared to other cartilages in the larynx, such as the thyroid and cricoid cartilages.

Location in the Larynx

• The cuneiform cartilages are located in the aryepiglottic folds, which are membranous structures that extend from the sides of the epiglottis to the arytenoid cartilages. These folds help form the entrance to the larynx (the laryngeal inlet).
• They are positioned superior and slightly anterior to the corniculate cartilages, which sit atop the arytenoid cartilages. The cuneiform cartilages are embedded within the soft tissue, lateral to the arytenoid cartilages. This location places them toward the back of the larynx, where they contribute to the support of the laryngeal framework.

Relation to the Aryepiglottic Folds

• The cuneiform cartilages are an integral part of the aryepiglottic folds, which stretch from the arytenoid cartilages to the lateral edges of the epiglottis. These folds form the sides of the laryngeal inlet and play a role in protecting the airway by closing during swallowing.
• The cartilages lie within the aryepiglottic folds, helping to stiffen and maintain the shape of the folds. This support ensures that the aryepiglottic folds can efficiently protect the airway by closing over the laryngeal inlet when necessary.

Composition

• The cuneiform cartilages are composed of elastic cartilage, a type of cartilage that is flexible and resilient. Elastic cartilage contains elastin fibers that allow the cartilage to bend and return to its original shape without permanent deformation.
• This flexibility is important for the cuneiform cartilages, as they need to provide support to the soft tissues of the aryepiglottic folds while allowing these tissues to move during breathing, phonation, and swallowing.

Attachment and Support

• Unlike the larger laryngeal cartilages such as the thyroid and cricoid cartilages, the cuneiform cartilages do not have direct bony or cartilaginous attachments. Instead, they are embedded in the soft tissue of the aryepiglottic folds.
• Their support comes from their position within these folds, helping maintain the structure of the upper part of the larynx. The cuneiform cartilages contribute to the stabilization of the folds, especially during vocalization and protective airway closure.

Neighboring Structures

The cuneiform cartilages are closely associated with several key structures of the larynx:

• Corniculate Cartilages: These are small, horn-shaped cartilages that sit atop the arytenoid cartilages. The cuneiform cartilages are positioned just above and slightly in front of the corniculate cartilages.
• Arytenoid Cartilages: The arytenoid cartilages are pyramid-shaped cartilages that play a major role in the movement of the vocal cords. The cuneiform cartilages are lateral to the arytenoid cartilages, with both structures contributing to the aryepiglottic folds.
• Epiglottis: The epiglottis is a larger, leaf-shaped structure that protects the airway during swallowing. The aryepiglottic folds, which contain the cuneiform cartilages, extend from the sides of the epiglottis to the arytenoid cartilages, helping to form the laryngeal inlet.
• Aryepiglottic Folds: These folds house both the cuneiform and corniculate cartilages, contributing to the structural integrity and movement of the laryngeal inlet.

Vascular Supply

The cuneiform cartilages, being part of the laryngeal framework, share their blood supply with the laryngeal tissues.

• The primary blood supply comes from the superior laryngeal artery, a branch of the superior thyroid artery (itself a branch of the external carotid artery).
• Additional blood supply is provided by the inferior laryngeal artery, a branch of the inferior thyroid artery, which supplies blood to the lower parts of the larynx and associated structures.

Innervation

The innervation of the cuneiform cartilages is derived from the same nerve branches that supply the rest of the larynx.

Sensory and motor innervation to the cuneiform cartilages and the surrounding aryepiglottic folds is provided by the superior laryngeal nerve and the recurrent laryngeal nerve, both branches of the vagus nerve (cranial nerve X). The recurrent laryngeal nerve supplies most of the intrinsic muscles of the larynx, while the superior laryngeal nerve provides sensory input to the mucosa.

Lymphatic Drainage

The lymphatic drainage of the cuneiform cartilages follows the general lymphatic drainage pattern of the larynx.

Lymph from the upper part of the larynx, including the cuneiform cartilages, drains into the deep cervical lymph nodes and the prelaryngeal lymph nodes. These nodes are responsible for filtering lymph and preventing infections from spreading from the laryngeal region.

Function

The cuneiform cartilages are small but play an essential role in maintaining the structure and function of the larynx. Although their contribution is subtle compared to the larger cartilages, they are crucial for maintaining the integrity of the laryngeal inlet and ensuring proper airway protection. Below is a detailed explanation of their functions.

Structural Support for the Aryepiglottic Folds

The primary function of the cuneiform cartilages is to provide structural support to the aryepiglottic folds.

• Maintaining the Shape of the Aryepiglottic Folds: The aryepiglottic folds form the borders of the laryngeal inlet and extend from the arytenoid cartilages to the sides of the epiglottis. The cuneiform cartilages are embedded within these folds, and their presence helps maintain the shape and stiffness of the folds. This structural support is important for ensuring that the aryepiglottic folds do not collapse, which would obstruct the laryngeal inlet.
• Tension and Stability: By stiffening the aryepiglottic folds, the cuneiform cartilages allow the folds to function properly during phonation and breathing. Without the support provided by these cartilages, the aryepiglottic folds might sag or lose tension, affecting the structure and function of the larynx.

Protection of the Laryngeal Inlet

The cuneiform cartilages play a role in protecting the laryngeal inlet, the opening that leads to the vocal cords and lower respiratory tract.

• Support During Swallowing: During swallowing, the larynx moves upward, and the epiglottis folds down to cover the laryngeal inlet, preventing food and liquids from entering the trachea. The cuneiform cartilages, by maintaining the integrity of the aryepiglottic folds, contribute to the effective closure of the laryngeal inlet during this process. This ensures that the airway is fully protected during swallowing, reducing the risk of aspiration.
• Reinforcement of the Aryepiglottic Folds: The aryepiglottic folds close tightly over the laryngeal inlet during swallowing and vocalization to ensure that no foreign material enters the airway. The cuneiform cartilages, acting as stiffeners, reinforce these folds to make the closure more effective. Their presence ensures that the folds do not collapse or fold inwards under the pressure of swallowing or breathing, helping to maintain a clear and protected airway.

Facilitating Phonation and Airway Control

The cuneiform cartilages contribute indirectly to phonation and the control of the airway by stabilizing the structures involved in voice production and breathing.

• Assistance in Voice Production: Although the cuneiform cartilages do not directly control the vocal cords, their support of the aryepiglottic folds helps ensure that the vocal tract remains stable during phonation. This stability is important for producing consistent, clear sounds. The aryepiglottic folds play a role in regulating the airflow through the larynx, and the cuneiform cartilages help ensure that these folds maintain their shape during speech or singing.
• Airway Control During Breathing: By supporting the aryepiglottic folds, the cuneiform cartilages help maintain the shape of the upper airway, ensuring that it remains open during breathing. Proper airway control is essential for regulating airflow during both inhalation and exhalation. The cuneiform cartilages prevent the aryepiglottic folds from collapsing inward during heavy breathing or physical exertion, ensuring that the airway remains open and unimpeded.

Contributing to the Laryngeal Framework

While small, the cuneiform cartilages are part of the laryngeal framework, contributing to the overall structural integrity of the larynx.

• Collaborative Role in Laryngeal Support: The cuneiform cartilages work in conjunction with the corniculate cartilages and arytenoid cartilages to form a supporting framework for the laryngeal inlet. Together, these cartilages ensure that the soft tissues of the larynx maintain their shape and function properly during activities such as speaking, swallowing, and breathing.
• Laryngeal Resilience: The presence of the cuneiform cartilages within the aryepiglottic folds adds to the resilience of the laryngeal structures. Their flexibility, due to the elastic cartilage composition, allows them to withstand the stresses of repetitive movement during vocalization, breathing, and swallowing without becoming damaged or deformed.

Reinforcement of the Laryngeal Inlet in Phonation and Swallowing

The cuneiform cartilages assist in reinforcing the structures that are responsible for closing off the airway during both phonation (sound production) and swallowing.

• Assisting Epiglottic Function: When the epiglottis folds backward to close the laryngeal inlet, the aryepiglottic folds, which contain the cuneiform cartilages, play a role in helping the epiglottis fully seal the airway. The cuneiform cartilages maintain the firmness of these folds to ensure that the airway is properly closed during swallowing, preventing choking or aspiration.
• Supporting the Laryngeal Vestibule: The vestibule of the larynx, which is the region above the vocal folds, is supported by the aryepiglottic folds, which in turn are reinforced by the cuneiform cartilages. This support helps maintain the structure and tension necessary for both protecting the airway and facilitating phonation.

Clinical Significance

The cuneiform cartilages play an essential role in maintaining the structure of the laryngeal inlet and the integrity of the aryepiglottic folds. While small and less prominent than other laryngeal cartilages, their dysfunction or damage can affect the protective mechanisms of the airway. Conditions affecting the cuneiform cartilages may compromise the stability of the aryepiglottic folds, leading to issues with airway closure during swallowing and an increased risk of aspiration or choking.

In certain laryngeal disorders, such as laryngomalacia—a condition where the soft tissues of the larynx collapse inward during breathing—the role of the cuneiform cartilages becomes clinically significant. Proper structural support from these cartilages helps prevent the collapse of the aryepiglottic folds, which is essential for maintaining a clear airway, particularly in infants and children who are more prone to airway obstruction. During laryngeal surgeries or procedures, awareness of the cuneiform cartilages’ location helps avoid inadvertent damage, which could affect airway stability and voice production.