Dominic Stone
The larynx, or voice box, is an organ in the neck involved in breathing, producing sound, and protecting the trachea against food aspiration. The muscles of the larynx can be divided into two groups: extrinsic and intrinsic. The extrinsic muscles act to elevate or depress the larynx during swallowing, while the intrinsic muscles act to move the individual components of the larynx, playing a vital role in breathing and
| Characteristics | Values |
|---|---|
| Larynx function | Involved in breathing, producing sound, and protecting the trachea against food aspiration |
| Larynx opening | Laryngeal inlet is about 4-5 centimeters in diameter |
| Larynx components | Cartilages, ligaments, membranes, and muscles |
| Muscle groups | Intrinsic (internal) and extrinsic (external) |
| Intrinsic muscle function | Control the shape of the rima glottidis (opening between the vocal folds and arytenoid cartilages), and the length and tension of the vocal folds |
| Extrinsic muscle function | Elevate or depress the larynx during swallowing |
| Intrinsic laryngeal muscles | Cricothyroid, Thyroarytenoid, lateral and posterior Cricoarytenoid, Interarytenoid, and more |
| Extrinsic laryngeal muscles | Suprahyoid (stylohyoid, digastric, mylohyoid, geniohyoid) and infrahyoid (sternohyoid, omohyoid, sternothyroid, thyrohyoid) |
| Muscle-related disorders | Laryngeal paralysis, Duchenne muscular dystrophy |
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What You'll Learn
Posterior cricoarytenoid muscles
The posterior cricoarytenoid muscle is an intrinsic muscle of the larynx. It is the only muscle that abducts the vocal cords, thereby opening the rima glottidis. This is important for breathing and speech. The muscle originates from the posterior surface of the cricoid cartilage and attaches to the muscular process of the arytenoid cartilage. It is innervated by the recurrent laryngeal nerve, specifically the inferior laryngeal nerve, which is a branch of the recurrent laryngeal nerve. The recurrent laryngeal nerve carries information from the vagus nerve.
The posterior cricoarytenoid muscle rotates the arytenoid cartilages laterally, pulling them posterolaterally. This movement separates the vocal cords and assists other intrinsic muscles in lengthening the vocal cords, allowing for the passage of air during inspiration and expiration. This makes the posterior cricoarytenoid muscle crucial for respiration. Its paralysis may lead to asphyxia, as it is the only muscle that opens the glottis, enabling breathing.
The posterior cricoarytenoid muscle also participates in the production of unvoiced sounds, such as letters that do not require vibration of the vocal cords. Failure of this muscle's function is often due to damage to the recurrent laryngeal nerve, which can occur during thyroidectomy operations or due to diseases affecting surrounding organs. Symptoms of unilateral recurrent laryngeal nerve palsy include hoarseness and reduced vocal stamina, while bilateral palsy can be life-threatening due to potential asphyxiation.
The posterior cricoarytenoid muscle is supplied by the laryngeal branches of the superior and inferior thyroid arteries. These arteries are branches of the external carotid and subclavian arteries, respectively. The muscle fibres vary in orientation, with the superior-most fibres being nearly horizontal, the intermediate fibres obliquely oriented, and the inferior-most fibres almost vertical. This variation in fibre orientation suggests that different movements may be produced depending on which portion of the muscle contracts.
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Lateral cricoarytenoid muscles
The lateral cricoarytenoid muscle is an intrinsic muscle of the larynx. It is involved in the production of sound, or phonation, by moving the various parts of the larynx and changing the state of the vocal folds. The intrinsic laryngeal muscles, of which the lateral cricoarytenoid is a part, are all involved in the production of sound. They do so by moving the various parts of the larynx, changing the state of the vocal folds (i.e. tension and length) and opening or closing the rima glottidis.
The lateral cricoarytenoid muscle is a bilateral muscle attaching between the cricoid and arytenoid cartilages of the larynx. It is innervated by the vagus nerve through the anterior branches of the recurrent laryngeal nerve. The muscle is located laterally to the vocal folds. Its insertion is closely related to the transverse arytenoid and posterior cricoarytenoid muscles as they all insert into the muscular process of the arytenoid cartilage.
The lateral cricoarytenoid is one of the classical adductor muscles involved in controlling the degree of glottis closure by rotating the arytenoid cartilages towards the midline. When the lateral cricoarytenoid muscles contract, they rotate the arytenoid cartilages and thus medially swing the vocal process onto which the vocal ligaments are attached. This brings the tips of the vocal processes together, resulting in adduction of the vocal folds and closure of the anterior part of the rima glottidis.
The main function of the lateral cricoarytenoid muscle is to aid sound production by adducting the vocal folds. It is one of the adductors, which close the glottis by pulling the back end of the arytenoid cartilages apart. This pulls the front ends together, making the vocal folds come together. The larynx, commonly called the voice box, is an organ in the top of the neck involved in breathing, producing sound, and protecting the trachea against food aspiration.
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Cricothyroid muscles
The cricothyroid muscles are one of the intrinsic laryngeal muscles, accompanied by six other muscles. They are small, bilaterally paired muscles found deep in the anterior compartment of the neck. The cricothyroid muscle is also known as the 'singer's muscle' because it is important for creating forceful speech and altering the tone of voice.
The cricothyroid muscle produces tension and elongation of the vocal cords. They draw up the arch of the cricoid cartilage and tilt back the upper border of the cricoid cartilage lamina. The distance between the vocal processes and the angle of the thyroid is increased, elongating and thus tensing the vocal folds, resulting in higher pitch phonation. They work as antagonists to the posterior cricoarytenoid muscles.
The cricothyroid muscle can be injured during a cricothyroidotomy, an emergency surgical procedure used to establish an airway. The cricothyroid artery and the external branch of the superior laryngeal nerve approach the muscle from a superolateral angle as it travels toward the midline. The superior poles of the ipsilateral lobe and the pyramidal lobe (when present) of the thyroid gland also partially cover the cricothyroid muscles.
The cricothyroid muscle is separated from its contralateral fellow by a triangular space occupied by the cricothyroid ligament. It is caudal to the inferior border of the thyroid cartilage and medial to the cricoarytenoid joint. The infrahyoid muscles are located superficially to the cricothyroid muscle.
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Thyroarytenoid muscles
The thyroarytenoid muscle, also known as vocalis, is a broad, thin, and wide muscle that forms the body of the vocal fold. It is one of the intrinsic muscles of the larynx, along with the oblique arytenoid, transverse arytenoid, posterior cricoarytenoid, lateral cricoarytenoid, cricothyroid, aryepiglotticus, thyroepiglottic muscles, and vocalis. The thyroarytenoid muscle plays a crucial role in controlling sound production or phonation, a process requiring high-level neuromuscular coordination. It arises from the inner surface of the inferior part of the thyroid cartilage, near the midline, and the cricothyroid ligament. The muscle fibres pass backward and laterally, inserting into the base and anterior surface of the arytenoid cartilage.
The thyroarytenoid muscle has two parts with different attachments and directions, making its action rather complicated. Its main function is to draw the arytenoid cartilages forward toward the thyroid cartilage, relaxing and shortening the vocal folds. The deeper portion of the thyroarytenoid muscle, if acting separately, is believed to modify the elasticity and tension of the vocal folds. In contrast, the lateral portion rotates the arytenoid cartilage inward, narrowing the rima glottidis by bringing the two vocal folds together.
The thyroarytenoid muscle is involved in the production of speech, with a considerable number of its fibres extending into the aryepiglottic fold. Some of these fibres continue as far as the margin of the epiglottis, forming the thyroepiglotticus muscle. The thyroarytenoid muscle is innervated by the recurrent laryngeal nerve, a branch of the vagus nerve. It also receives a communicating branch from the external laryngeal nerve. The muscle is supplied by the laryngeal branches of the superior and inferior thyroid arteries and is drained by the internal jug.
The thyroarytenoid muscle helps regulate the length and tension of the vocal folds, along with the cricothyroid and vocalis muscles. The vocalis muscle is considered part of the thyroarytenoid muscle by some anatomists, while others describe it as a separate muscle. The thyroarytenoid muscle relaxes the vocal ligament, resulting in a softer voice. This muscle also has a force to strengthen glottic closure, bringing the vocal folds together and keeping them together to resist the airstream from the lungs.
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Suprahyoid and infrahyoid muscles
The neck contains several muscles, which are classified based on their relationship to the hyoid bone. Muscles above the hyoid bone are called "suprahyoid muscles", while those below are called "infrahyoid muscles".
Suprahyoid muscles facilitate chewing, swallowing, and phonation. They also assist with neck flexion and play a crucial role in airway management. They are made up of four muscles: digastric, stylohyoid, mylohyoid, and geniohyoid. The suprahyoid muscles are primarily supplied by branches of the facial artery, with the occipital and lingual arteries also contributing. The digastric muscle, which is a spindle-shaped structure with two bellies, is innervated by the digastric branch of the facial nerve. The anterior belly is innervated by the inferior alveolar nerve, a branch of the mandibular nerve. The geniohyoid is located on either side of the midline of the neck, deep to the mylohyoid muscle.
Infrahyoid muscles, on the other hand, stabilize the hyoid bone. When they contract, they depress the hyoid bone, allowing the suprahyoid muscles to contract and depress the mandible. There are four infrahyoid muscles: omohyoid, sternohyoid, sternothyroid, and thyrohyoid. The majority of these muscles are innervated by the ansa cervicalis in their lower half.
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Frequently asked questions
The muscles of the larynx can be divided into two groups: extrinsic (external) muscles and intrinsic (internal) muscles.
The extrinsic muscles act to elevate or depress the larynx during swallowing. They are attached to the hyoid bone and move the thyroid cartilage.
The intrinsic muscles move the individual components of the larynx, playing a vital role in breathing and
The posterior cricoarytenoid muscles are the abductors of the vocal folds, and thus the only muscle capable of widening the rima glottidis. They open the glottis by pulling the back ends of the arytenoid cartilages together, pulling the front ends apart.
The adductors of the vocal folds are the lateral cricoarytenoid muscles. They narrow the rima glottidis, modulating the tone and volume of speech. They close the glottis by pulling the back ends of the arytenoid cartilages apart, pulling the front ends together.
