The larynx is a structure in the neck made up of four basic anatomical unit: the skeleton, muscles of the inner, outer muscles and mucosa. The most important part of laryngeal skeleton consists of cartilages: three single (epiglottic, cricoid, and thyroid) and three paired (cuneiform, arytenoid, corniculate). Muscles of the larynx are connected to the cartilages. One of the internal muscles (in the larynx), musculus vocalis ( a part of arytenoid muscle), extends from each side of the arytenoid cartilage to the interior of the thyroid cartilage down to the rear of the Adam’s apple, forming the body of the vocal cords. Vocal cords act as an oscillator or source of voice in vocal tract. The space between the vocal cords is called the glottis. Internal muscles change the position, shape and tension of the vocal cords, bringing them together (adduction), or separating them (abduction) or stretch.
Arytenoid cartilage are also capable of rotation and sliding thus allowing complex movement of vocal cords and changing their edges. All but one muscle on each side of the larynx are inervated to one of two laryngeal nerves. This nerve, which has a long trajectory, it goes from the neck down into the chest and back in the larynx it can be easily damaged by trauma, neck or chest surgery, which can result in vocal cord paralysis. The remaining muscle (cricoid) is inervated to the superior laryngeal nerve on each side, and it is therefore susceptible to viral and traumatic injury. “false ” vocal cords are located above the true vocal cords, and unlike the true ones, they do not not touch each other during speaking or singing.
Therefore, the elastic fixing of laryngeal cartilages, cartilage positions change in relation to one another when the laryngeal skeleton is raised or lowered. Such changes are controlled externally and vertically (from the outside of the larynx), laryngeal muscles, or muscles of the neck. When the angles and the distance between the cartilages changes to the effect of “accordion”, the remaining length of the inner muscle is changing as a result. Such a significant adjustment in the position of the internal muscle opposes to the fine control of the smooth voice quality.
Classical singers learn how to avoid the natural tendency of the larynx to rise to the height, and descend with the reduction in height, thereby increasing units of vocal quality. Singing techniques may be different in singers from Asia, India, Arabia, with a different aesthetic values.
Mucosa is a soft tissue that forms a thin surface that lubricates the vocal cords and makes contact when they are merged. In addition to the mucosal surface there is also squamous epitelium. The top layer of the lamina propria is more below, and it is connected to the basic membrane, known as Reinke’s area and it consists of loose fibrous components and matrices. It also shows a tendency for fluid accumulation. The epithelium is attached to the superficial layer of the lamina propria through the base membrane.
Central layer of the lamina propria contains elastic fibers and a moderate number of fibroblasts. The deeper layer is rich in fibroblasts and contains collagen fibers. Different fibers have different mechanical properties that are important for smooth movements (without barriers) that are necessary for the right vocal cord vibration. The structure contains a vocal cover (epithelium and superficial layer of lamina propria), transition (middle and deeper layers of the lamina propria) and body (vocal muscle).