Arytenoid cartilage

The arytenoid cartilages are a pair of small, pyramid-shaped cartilages located within the larynx. These cartilages are essential components of the laryngeal framework and are involved in the movement and control of the vocal cords. Each arytenoid cartilage has a triangular shape with three surfaces, and they serve as the primary anchor points for the vocal cords.

Location

The arytenoid cartilages are situated on the superior border of the cricoid cartilage in the posterior aspect of the larynx. They sit atop the cricoid cartilage’s lamina, positioned symmetrically on both sides of the midline. These cartilages are located just above the trachea, near the back of the throat, and are connected to other laryngeal structures, including the vocal cords and muscles that control their movement.

Structure and Anatomy

The arytenoid cartilages are vital components of the larynx that play a significant role in the movement of the vocal cords. They are small, pyramid-shaped structures located symmetrically within the posterior aspect of the larynx. Their shape and attachments allow for intricate movements necessary for vocal cord positioning and tension adjustments. Below is a detailed description of the anatomy of the arytenoid cartilages.

Shape and Structure

• The arytenoid cartilages are pyramidal in shape, with three surfaces, a base, and an apex. They are typically triangular or pyramid-like, allowing for various attachments of muscles and ligaments that control the vocal cords.
• Each cartilage has three prominent surfaces:
• • Posterior surface: This surface is convex and smooth, and it faces backward. It provides the point of attachment for muscles responsible for controlling the movement of the arytenoids.
  • Medial surface: This surface faces the opposite arytenoid cartilage and is involved in the closing of the vocal cords. It is flat and smooth.
  • Anterolateral surface: This surface faces forward and outward. It provides points of attachment for several key muscles and ligaments that help in vocal cord control.
• The apex of the arytenoid cartilage is pointed and curves slightly backward and medially. It serves as an attachment point for the corniculate cartilage and is involved in stabilizing the aryepiglottic folds.

Base of the Arytenoid Cartilage

The base of the arytenoid cartilage is concave and fits into the cricoarytenoid joint, which allows the arytenoid cartilages to move in various directions. The base has two projections:

• Vocal process: This is a pointed projection that extends anteriorly. The vocal cords (or vocal ligaments) attach to this process. It plays a crucial role in adjusting the tension and positioning of the vocal cords.
• Muscular process: This projection extends laterally from the base and provides an attachment for several muscles, including the posterior cricoarytenoid muscle and lateral cricoarytenoid muscle, which are involved in the movement of the arytenoid cartilages.

Articulation with the Cricoid Cartilage

• The arytenoid cartilages articulate with the cricoid cartilage through the cricoarytenoid joint, a synovial joint that allows for a wide range of movements, including rotation, tilting, and gliding. This joint is located at the superior border of the cricoid lamina, and the concave base of the arytenoid cartilage fits into this joint, allowing for smooth, controlled movements necessary for vocal cord adjustments.
• The movements of the arytenoid cartilages through this joint are essential for the opening and closing of the vocal cords during phonation and respiration.

Ligaments and Membranes Associated with the Arytenoid Cartilages

Several ligaments and membranes connect the arytenoid cartilages to other structures in the larynx, providing support and facilitating movement.

• Vocal Ligament: The vocal ligament attaches to the vocal process of the arytenoid cartilage. It runs forward to the thyroid cartilage, forming the structural core of the vocal cords. The tension of this ligament can be adjusted by the movements of the arytenoid cartilages, allowing for changes in pitch and sound.
• Quadrangular Membrane: This membrane extends between the arytenoid cartilages and the epiglottis. The upper border of this membrane forms the aryepiglottic fold, which includes the arytenoid cartilages and helps protect the airway during swallowing.
• Cricoarytenoid Ligaments: The posterior cricoarytenoid ligament and the anterior cricoarytenoid ligament support the cricoarytenoid joint. These ligaments stabilize the joint and control the range of motion of the arytenoid cartilages, ensuring that their movements are smooth and within the necessary range for vocal cord function.

Muscles Associated with the Arytenoid Cartilages

Several important muscles control the movement of the arytenoid cartilages, allowing for precise regulation of the vocal cords.

• Posterior Cricoarytenoid Muscle: This muscle is the primary abductor of the vocal cords, meaning it pulls the arytenoid cartilages outward, separating the vocal cords and opening the airway during breathing.
• Lateral Cricoarytenoid Muscle: This muscle is responsible for adducting the vocal cords, or pulling them together. It rotates the arytenoid cartilages inward, closing the airway and bringing the vocal cords together for phonation.
• Thyroarytenoid Muscle: This muscle runs parallel to the vocal cords and helps relax them by pulling the arytenoid cartilages forward. This reduces tension on the vocal cords, allowing for lower-pitched sounds.
• Interarytenoid Muscle: This muscle runs between the two arytenoid cartilages and brings them together, further closing the glottis and assisting in vocal cord adduction.

Blood Supply

The blood supply to the arytenoid cartilages is derived from the superior laryngeal artery and the inferior laryngeal artery, which are branches of the superior thyroid artery and inferior thyroid artery, respectively.

• Superior Laryngeal Artery: This artery supplies blood to the upper part of the larynx, including the arytenoid cartilages.
• Inferior Laryngeal Artery: This artery supplies the lower part of the larynx and the surrounding structures, including parts of the cricoarytenoid joint and the arytenoid cartilages.

Innervation

The arytenoid cartilages and the muscles that control them are innervated by branches of the vagus nerve (cranial nerve X).

• Recurrent Laryngeal Nerve: This nerve provides motor innervation to most of the muscles controlling the arytenoid cartilages, including the posterior and lateral cricoarytenoid muscles, the thyroarytenoid muscle, and the interarytenoid muscle. The recurrent laryngeal nerve also supplies sensory innervation to the area below the vocal cords.
• Superior Laryngeal Nerve: This nerve provides sensory innervation to the mucosa of the larynx, including the area surrounding the arytenoid cartilages.

Lymphatic Drainage

Lymphatic drainage from the arytenoid cartilages is directed to the deep cervical lymph nodes, which help filter lymph and prevent infections or inflammation from spreading in the larynx.

Deep Cervical Lymph Nodes: These lymph nodes are part of the lymphatic system that drains the laryngeal tissues, including the arytenoid cartilages.

Function

The arytenoid cartilages play a pivotal role in the movement and regulation of the vocal cords, which are essential for breathing, phonation (voice production), and protecting the airway. Below is a detailed explanation of the functions of the arytenoid cartilages.

Control of Vocal Cord Movement

The primary function of the arytenoid cartilages is to control the position and movement of the vocal cords, which are critical for regulating airflow through the larynx and enabling sound production.

• Abduction (Opening the Vocal Cords): The arytenoid cartilages move outward to separate the vocal cords, a process known as abduction. This movement widens the space between the vocal cords (the glottis), allowing air to pass freely into the trachea and lungs. Abduction is essential for breathing, especially during deep inhalation, as it ensures that the airway is fully open for maximum airflow. The posterior cricoarytenoid muscle is responsible for this movement.
• Adduction (Closing the Vocal Cords): The arytenoid cartilages also move inward to bring the vocal cords together, a process called adduction. This movement closes the glottis, preventing air from flowing through the larynx. Adduction is crucial for phonation, as the vocal cords must be brought close together to vibrate and produce sound when air is expelled from the lungs. The lateral cricoarytenoid muscle and interarytenoid muscle control adduction.

Phonation (Voice Production)

The arytenoid cartilages play a critical role in voice production by positioning the vocal cords for optimal vibration, which is necessary for generating sound.

• Vibration of Vocal Cords: For phonation to occur, the vocal cords must be brought together by the arytenoid cartilages. When air from the lungs passes through the closed vocal cords, they vibrate, producing sound. The precise movement of the arytenoid cartilages ensures that the vocal cords are in the correct position to vibrate efficiently, allowing for clear voice production.
• Pitch Control: The arytenoid cartilages help regulate the tension of the vocal cords, which affects the pitch of the sound produced. By tilting or gliding the arytenoids forward, the vocal cords become looser, resulting in lower-pitched sounds. Conversely, when the arytenoids tilt backward, the vocal cords are stretched, producing higher-pitched sounds. This ability to adjust tension and position is essential for modulating vocal pitch during speech or singing.

Airway Protection During Swallowing

The arytenoid cartilages play an important role in protecting the airway during swallowing by closing the vocal cords and the glottis.

• Prevention of Aspiration: When swallowing, the arytenoid cartilages adduct the vocal cords, bringing them together to close the glottis. This closure prevents food, liquids, and foreign objects from entering the trachea and lungs, reducing the risk of aspiration. The interarytenoid muscle helps ensure that the arytenoid cartilages are tightly drawn together during swallowing, effectively sealing off the airway.
• Coordination with the Epiglottis: The arytenoid cartilages work in coordination with the epiglottis, which folds down over the laryngeal inlet during swallowing. The closure of the vocal cords, combined with the downward movement of the epiglottis, creates a double-layered defense mechanism that protects the airway from ingested material.

Adjustment of Glottal Width

The arytenoid cartilages regulate the width of the glottis, the opening between the vocal cords, which is crucial for controlling airflow through the larynx during various physiological processes.

• Breathing: During normal breathing, the arytenoid cartilages adjust the glottal width to allow a sufficient amount of air to pass through the larynx. For quiet breathing, the vocal cords are partially abducted, leaving the glottis open but not fully widened. During heavy breathing or physical exertion, the arytenoid cartilages fully abduct the vocal cords to widen the glottis, ensuring maximum airflow into the lungs.
• Coughing and Sneezing: When coughing or sneezing, the arytenoid cartilages briefly close the vocal cords, creating high pressure beneath the glottis. Upon sudden opening, air is forcefully expelled, helping to clear irritants or foreign objects from the airway.

Fine Control of Voice Quality and Loudness

The arytenoid cartilages provide fine control over the position and tension of the vocal cords, enabling adjustments in voice quality, loudness, and tone.

• Volume Control: The arytenoid cartilages control the degree to which the vocal cords are brought together during phonation. A tight adduction of the vocal cords results in a louder voice, as more subglottic pressure is required to push air through the vocal cords. Conversely, a less tight adduction produces a softer voice, as less pressure is required.
• Voice Timbre and Tone: The precise movement of the arytenoid cartilages allows for subtle adjustments in the vocal cords’ tension, affecting the timbre and tone of the voice. This control is particularly important for singers, who rely on the fine movements of the arytenoids to achieve the desired vocal quality and range.

Stabilization of the Laryngeal Structure

The arytenoid cartilages contribute to the overall stability of the laryngeal structure by anchoring the vocal cords and providing attachment points for key muscles and ligaments.

• Anchor for Vocal Ligaments: The arytenoid cartilages serve as the posterior anchor points for the vocal ligaments, which form the core of the vocal cords. This anchoring function ensures that the vocal cords remain properly aligned and stable during phonation and respiration.
• Support for Muscular Attachments: Several important muscles, such as the posterior and lateral cricoarytenoid muscles, attach to the arytenoid cartilages. These muscles are responsible for controlling the movement of the arytenoid cartilages and, by extension, the vocal cords. The stable base provided by the arytenoid cartilages ensures that these muscles can function efficiently.

Clinical Significance

The arytenoid cartilages play a critical role in voice production, airway protection, and breathing. Dysfunction or injury to these cartilages can lead to significant clinical issues, including vocal cord paralysis, dysphonia (voice disorders), and breathing difficulties. Conditions such as arytenoid dislocation or fracture can occur due to trauma, intubation, or laryngeal surgery, affecting the movement of the vocal cords and leading to hoarseness or airway obstruction.

Cricoarytenoid arthritis, commonly associated with rheumatoid arthritis, can cause inflammation of the cricoarytenoid joint, resulting in painful and restricted movement of the arytenoid cartilages. This can lead to symptoms such as voice changes, difficulty swallowing, and breathing difficulties. Additionally, laryngeal cancer involving the arytenoid cartilages may require surgical intervention, affecting vocal cord function. Therefore, the health and integrity of the arytenoid cartilages are crucial for maintaining proper vocal and respiratory function.