Anatomy and Physiology

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Anatomy & Physiology of the Voice

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. 

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. 
 

 Larynx  Larynx
Copyright, Blue Tree Publishing
Copyright, Blue Tree Publishing

 
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. 
 

 Larynx  Larynx
Copyright, Blue Tree Publishing
Copyright, Blue Tree Publishing


 
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.).  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.

The intrinsic laryngeal muscles are described as such because both of their attachments are within the larynx.  The intrinsic muscles include the interarytenoid, lateral cricoarytenoid, posterior cricoarytenoid,  cricothyroid, and thyroarytenoid (true vocal cord) muscles.  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.  
 

Vocal cords
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Videostroboscopic View of the Larynx
Read an explanation of this examination online.

The larynx houses the vocal cords, two elastic bands of tissue (right and left) that form the entryway into the trachea (airway).  Above and to the sides of the true vocal cords are the false vocal cords, or ventricular cords.  The false vocal cords do not usually vibrate during voicing, but are often seen coming together (adducting) in individuals with muscle tension dysphonia, a common voice disorder characterized by excessive muscular tension with voice production. The true vocal cords open (abduct) when we are breathing and close (adduct) during voicing, coughing, and swallowing.

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