Anatomy of Voice Production

Voice production is a complex process that actually involves practically almost all systems of the body.  The process begins with respiration (breathing). As air is inhaled, the diaphragm (the large, horizontal muscle below the lungs) lowers, the volume of the lungs expand, and air rushes in to fill the space.  When we exhale, the muscles of the rib cage lower, the diaphragm raises, therefore expelling out air. 

In order for us to produce sound, the adductor muscles (the "vocal cord closers") will have to work to provide resistance to the exhaled air from the lungs.  This air will then burst through the closed vocal cords creating vibration.  As air rushes through the vocal cords, the pressure between the cords will drop, pulling them back together (Bernoulli Effect).  This vibration, or the action of the vocal cords being blown apart and then "sucked" back together will be repeated hundreds or even thousands of times per second, producing what we call our “voice".  This sound which originates at the level of the vocal cords, then goes through the pharynx (throat) and oral cavity (including the lips, tongue, palate, and jaw) to create speech. 

The larynx, also popularly known as 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, 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 largest of the unpaired cartilages, the thyroid cartilage, resembles a shield in terms of its shape.  The most anterior portion of this cartilage is very prominent in some men, and is commonly referred to as an "Adam's apple."  Everyone actually has an “Adam’s Apple” though it is more prevalently obvious in men.

The second unpaired cartilage, the cricoid cartilage, is often described as a "signet ring."  The third unpaired cartilage is the epiglottis, which is shaped like a leaf.  The physical property of the epiglottis allows it to invert to direct food and liquid to the esophagus to in turn protect the vocal cords and airway during swallowing.

The three paired cartilages include the arytenoid, cuneiform, and corniculate cartilages.  The arytenoids are a point of attachment for the vocal cords, allowing the opening and closing movement of the vocal cords which is necessary for respiration and voice production.  The other 2 cartilages, cuneiform and corniculate, are very small, and have no specialized function.

There are also two primary groups of laryngeal muscles, the extrinsic and the intrinsic muscle.  The extrinsic muscle group is the one that attach to a site within the larynx and to a site outside the larynx (such as the hyoid bone, jaw, etc.).  There are eight (8) extrinsic laryngeal muscles and they are further subdivided into the supra-hyoid group (above the hyoid bone), and the infrahyoid group (below the hyoid bone).  The suprahyoid group includes the stylohyoid, mylohyoid, geniohyoid, and the digastric muscles and they work together to raise the larynx. The infrahyoid group on the other hand includes the sternothyroid, sternohyoid, thyrohyoid, and omohyoid muscles and they work together to lower the hyoid bone and larynx.

The intrinsic laryngeal muscle group is 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 these muscles are paired with the exception of the transverse interarytenoid.  All of the intrinsic laryngeal muscles work together to close (adduct) the vocal cords with the exception of the posterior cricoarytenoid, which is the only intrinsic laryngeal muscle that opens (abducts) the vocal cords. 

The larynx (voice box) houses the vocal cords, two elastic bands of tissue on the left and the right side that forms the entryway into the trachea (airway).  On the sides and at the top of the true vocal cords are the ventricular cords or the false vocal cords.  The false vocal cords do not usually vibrate to help produce voice, but are usually observed adducting in people with muscle tension dysphonia, a voice disorder characterized by excessive muscular tension with voice production. The true vocal cords abduct(open) when we breathe and adduct(close) when we voice, cough, or even swallow.