Laryngeal cartilages <ul><li>The laryngeal skeleton consists of nine cartilages : </li></ul><ul><li>three single ( thyroid , cricoid, and epiglottic) </li></ul><ul><li>three paired (arytenoid, corniculate , and cuneiform). </li></ul><ul><li>The hyoid bone is not part of the larynx, though it is connected to it. </li></ul><ul><li>The larynx extends vertically from the tip of the epiglottis to the inferior border of the cricoid cartilage . </li></ul>
Laryngeal joints : Cricoarytenoid joint :Its synovial joint surrounded by capsular ligament,formed between the base of arytenoid and upper border of cricoid lamina.Two types of movements—a)rotatory ,b)gliding movement. Cricothyroid joint : Its also a synovial joint.Each is formed by the inferior cornua of thyroid cartilage with a facet on the cricoid cartilage.
muscles There are two primary groups of laryngeal muscles, extrinsic and instrinsic. The extrinsic muscles are described as such because they attach to a site within the larynx and to a site outside of the larynx (such as the hyoid bone, jaw, etc.). The intrinsic laryngeal muscles are described as such because both of their attachments are within the larynx.
Intrinsic muscles associated with the larynx Cricothyroid muscles lengthen and stretch the vocal folds. Posterior cricoarytenoid muscles abduct and externally rotate the arytenoid cartilages, resulting in abducted vocal cords. Lateral cricoarytenoid muscles adduct and internally rotate the arytenoid cartilages, which can result in adducted vocal folds. Transverse arytenoid muscle adducts the arytenoid cartilages, resulting in adducted vocal cords.  Oblique arytenoid muscles narrow the laryngeal inlet by constricting the distance between the arytenoid cartilages and epiglottis. Vocalis muscles adjust tension in vocal folds. Thyroarytenoid muscles - sphincter of vestibule, narrowing the laryngeal inlet. All of the intrinsic muscles are paired (that is, there is a right and left muscle) with the exception of the transverse interarytenoid. All of the intrinsic laryngeal muscles work together to adduct (close) the vocal cords with the exception of the posterior cricoarytenoid, which is the only muscle that abducts (opens) the vocal cords.
Extrinsic muscles associated with the larynx <ul><li>Thyrohyoid muscles </li></ul><ul><li>Sternothyroid muscles </li></ul><ul><li>Inferior constrictor muscles </li></ul><ul><li>Digastric </li></ul><ul><li>Stylohyoid </li></ul><ul><li>Mylohyoid </li></ul><ul><li>Geniohyoid </li></ul><ul><li>Hyoglossus </li></ul>There are eight extrinsic laryngeal muscles, and they are further divided into the suprahyoid group (above the hyoid bone) and the infrahyoid group (below the hyoid bone). The suprahyoid group includes the stylohyoid, mylohyoid, geniohyoid, and digastric muscles. The suprahyoid extrinsic laryngeal muscles work together to raise the larynx. The infrahyoid group includes the sternothyroid, sternohyoid, thyrohyoid, and omohyoid muscles. The infrahyoid extrinsic laryngeal muscles work together to lower the hyoid bone and larynx.
Function of the larynx <ul><li>Phonation </li></ul><ul><li>Respiration </li></ul><ul><li>Fixation of chest </li></ul><ul><li>Protection of lower respiratory tract </li></ul>
Relationship between function and structure of larynx <ul><li>In order to perform its specific function, larynx has special corresponding structural characteristics:- </li></ul>
phonation Sound Production Sound production occurs due to the vibration of the mucosa at the inner edge of each vocal cord. Thus any structural, inflammatory, or neoplastic lesion of the vocal cord affects voice production and quality (Fig.3). Voice production is a complex action, and involves practically all systems of the body. Voice production begins with respiration (breathing). Air is inhaled as the diaphragm (the large, horizontal muscle below the lungs) lowers. The volume of the lungs expands and air rushes in to fill this space. We exhale as the muscles of the rib cage lower and the diaphragm raises, essentially squeezing the air out.
Voice production <ul><li>In order to produce sound, adductor muscles (the "vocal cord closers") are activated, providing resistance to exhaled air from the lungs. Air then bursts through the closed vocal cords. As the air rushes through the vocal cords, the pressure between the cords drops, sucking them back together. This is known as the "Bernoulli Effect." This vibration, or the action of the vocal cords being blown apart and then "sucked" back together, is repeated hundreds or even thousands of times per second, producing what we hear as voice. This sound, created at the level of the vocal cords, is then shaped by muscular changes in the pharynx (throat) and oral cavity (including the lips, tongue, palate, and jaw) to create speech. </li></ul>
The larynx (lar-inks), commonly called the "voice box," is a tube shaped structure comprised of a complex system of muscle, cartilage, and connective tissue. The larynx is suspended from the hyoid bone, which is significant in that it is the only bone in the body that does not articulate with any other bone. The framework of the larynx is composed of three unpaired and three paired cartilages. The thyroid cartilage is the largest of the unpaired cartilages, and resembles a shield in shape. The most anterior portion of this cartilage is very prominent in some men, and is commonly referred to as an "Adam's apple." The second unpaired cartilage is the cricoid cartilage, whose shape is often described as a "signet ring." The third unpaired cartilage is the epiglottis, which is shaped like a leaf. The attachment of the epiglottis allows it to invert, an action which helps to direct food and liquid into the esophagus and to protect the vocal cords and airway during swallowing.
The three paired cartilages include the arytenoid, cuneiform, and corniculate cartilages. The arytenoids are shaped like pyramids, and because they are a point of attachment for the vocal cords, allow the opening and closing movement of the vocal cords necessary for respiration and voice. The cuneiform and corniculate cartilages are very small, and have no clear-cut function.
Innervation <ul><li>The larynx is innervated by branches of the vagus nerve on each side. Sensory innervation to the glottis and laryngeal vestibule is by the internal branch of the superior laryngeal nerve . The external branch of the superior laryngeal nerve innervates the cricothyroid muscle . Motor innervation to all other muscles of the larynx and sensory innervation to the subglottis is by the recurrent laryngeal nerve . While the sensory input described above is (general) visceral sensation (diffuse, poorly localized), the vocal fold also receives general somatic sensory innervation (proprioceptive and touch) by the superior laryngeal nerve. </li></ul><ul><li>Injury to the external laryngeal nerve causes weakened phonation because the vocal cords cannot be tightened. Injury to one of the recurrent laryngeal nerves produces hoarseness , if both are damaged the voice may or may not be preserved, but breathing becomes difficult. </li></ul>
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