The cricoid cartilage is a foundational, ring-shaped structure in the throat, forming the base of the laryngeal skeleton, which is commonly known as the voice box. Made of hyaline cartilage, it supports the upper airway and provides a protective framework for the respiratory passage. This structure helps ensure the continuous flow of air into the lungs.
Anatomical Placement in the Neck
The cricoid cartilage is situated low in the front of the neck, serving as a reliable landmark for medical professionals. Its position is immediately below the larger thyroid cartilage, the structure that forms the anterior prominence known as the Adam’s apple. This location marks the inferior boundary of the larynx, where the voice box transitions into the trachea. The cricoid cartilage attaches directly to the first cartilaginous ring of the trachea by a ligament.
The position of this cartilage corresponds closely to the sixth cervical vertebra (C6) in the spine. This vertebral level is frequently referenced in anatomical and surgical descriptions. Locating the cricoid externally is possible through palpation by gently moving downward from the thyroid cartilage prominence. A small, soft depression, the cricothyroid membrane, is felt first, followed by the firm, rounded structure of the cricoid arch.
Distinctive Shape and Structure
The physical design of the cricoid cartilage is unique within the respiratory system. It is the only laryngeal cartilage that forms a complete, uninterrupted ring around the entire circumference of the airway. This structural difference makes the cricoid cartilage significantly stronger and thicker than the thyroid cartilage directly above it. The specific morphology of the cricoid is frequently likened to a signet ring, highlighting its uneven circumference.
The structure consists of two distinct parts: a narrow anterior arch and a broad posterior lamina. The anterior arch is the slender, curved portion easily felt at the front of the neck, resembling the band of a ring. Conversely, the posterior lamina is a tall, quadrilateral sheet of cartilage that makes up the back part, similar to the flat face of a signet ring. The composition is primarily hyaline cartilage, which is characterized by its smooth nature and capacity to withstand compressive forces, making it well-suited for maintaining an open airway.
Primary Functions in Respiration and Voice
The structural integrity and unique placement of the cricoid cartilage enable it to perform two major biological roles related to breathing and sound production. Its primary function in respiration is maintaining the patency of the airway, meaning keeping the passage open. Because the cricoid is the only complete ring of cartilage in the upper airway, it acts as a rigid support that prevents the trachea from collapsing. This stability is particularly important during inhalation, when negative pressure is created within the chest cavity.
In terms of vocalization, the cricoid cartilage acts as a supporting foundation for the mechanics of speech. Its large posterior lamina provides a secure attachment site for other laryngeal cartilages, notably the paired arytenoid cartilages. These pyramid-shaped structures sit atop the cricoid’s posterior surface and connect to the vocal cords. The cricoid and arytenoids form a specialized joint that permits the arytenoids to rotate and slide, controlling the tension and position of the vocal cords to produce sound.