HOW VOICES WORK: BASIC VOCAL ANATOMY AND PHYSIOLOGY

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1 1 DRAFT excerpts from Chapter Three Rethinking Choir Pedagogy: Twenty-first Century Foundations James F. Daugherty, Ph.D. May not be used or circulated without permission. HOW VOICES WORK: BASIC VOCAL ANATOMY AND PHYSIOLOGY We begin this exploration by focusing primarily on anatomy. Anatomy has to do with study of the body s structure and form. Latter portions of this section also include some conceptual groundwork in physiology. Physiology addresses how body structures actually work and function. The explications that follow are designed to assist those with limited scientific backgrounds (that is, most choral-vocal music majors) to get ready for more in depth explorations found in books, research studies, and other media authored by voice scientists. In other words, the intention here is to offer a simultaneously accurate and user-friendly sequence of some basic facts and concepts. Even so, many students, particularly pre-professional undergraduates, may balk initially at the prospect of engaging with such material. It is human nature to ask, Why do I have to learn this stuff? This query, as is the case with most questions, is a logical and very appropriate one to pose. There is, as indicated in the introduction to this chapter, a reasonable, even compelling answer to that question. It bears repeating here: Because you work, or shortly will work, in a professional capacity with living human beings. Imprecise or just plain wrong understandings of vocal anatomy and physiology on your part, no matter how well-intentioned or sincerely held, can (a) potentially harm those persons entrusted to your care and (b) prevent you from devising strategies and learning opportunities that can actually help people achieve their fullest vocal and human potentials. Bluntly but succinctly put, ignorance of vocal anatomy, physiology, and acoustics is not an option for twenty-first century choral-vocal professionals. That said, let us roll up our sleeves and attend to the professional business now at hand. Definition and Description The Larynx The larynx (pronounced LAIR-inks) is a mobile body organ located in the neck. It is situated (a) in front of the spinal column, (b) below the base of the tongue, and (c) in front of and adjacent to the esophagus (the pathway for food and liquid from the mouth to the stomach). See Figure 3.1. The larynx basically forms a somewhat flexible, connecting tube. It is about one to two centimeters (or roughly 1.5 inches) long in adults. Sometimes the larynx is referred to, informally, as the voice box. It connects directly (a) to the respiratory system below it (trachea

2 2 [windpipe], bronchi, and lungs) and (b) to the vocal tract above it (the throat directly above the larynx, along with the oral cavity [mouth]). Larynx Figure 3.1. Location of the larynx, sagittal view. Image from GetBodySmart.com [permission pending] The larynx houses the vocal folds. As a unit, the larynx is largely suspended from a single bone, the hyoid (See Figure 3.2), which itself is suspended from the base of the skull by various muscles and ligaments. The fact that the larynx is suspended from the hyoid bone contributes to the capacity of the larynx as a whole to move up and down, and for various of its parts to gently slide, tilt, rotate, or rock back and forth. Hyoid bone

3 3 Hyoid bone Figure 3.2. The hyoid bone and suspension of the larynx, anterior view. Also attached to the hyoid bone is the root of the tongue. From the hyoid bone the tongue, of course, extends upward into the mouth. During swallowing, the base of the tongue moves backward and downward, while the larynx is drawn simultaneously forward and upward. In this fashion the base of the tongue shields and protects the larynx. The plural of larynx is larynges (pronounced lairingees). The adjectival form of the term is laryngeal (pronounced either lairingeeul or lairinjul), as in laryngeal cartilages. SIDEBAR: Viewing Anatomical Diagrams and Pictures. By custom, anatomical diagrams and pictures typically are labeled by terms that give the viewer important information about the angle, attitude, or direction of the body parts depicted. For example, Figure 3.1 is labeled a sagittal or side view of the larynx. Such information assists in visualizing spatially the orientation of particular body parts as they are represented in various diagrams and pictures. Among some basic, descriptive terms to know are: Supra- Sub- Anterior: Posterior: Superior: Inferior: a prefix meaning above or over toward the front a prefix meaning below or under toward the back toward the top toward the bottom

4 4 Medial: Lateral: Sagittal: Transverse: Oblique: toward the midline or mid plane of the body toward the body s sides, away from the midline an imagined anatomical plane that separates the body into right and left sides; a side view an imagined anatomical plane that divides the body crosswise; a perpendicular orientation a diagonal or sloping orientation These descriptors may be combined. For example, a view or depiction of the larynx labeled anterolateral combines the descriptors anterior and lateral. Such a view would encompass the front and side of a particular body part, or portion thereof. An important point to remember when viewing anatomical depictions is that such figures invariably simplify matters in order to advance particular understandings. Thus they may obscure purposely the overall complexity, even seeming messiness, of how particular human body parts relate to other body parts. It is not absolutely necessary for choral conductor-teachers to know all of the various tissues, muscles, membranes, ligaments, blood vessels, nerves, joints, and glands that surround, transverse, or weave in and out of those body parts of particular interest to singers and singing pedagogues. After all, their professional duties do not include practicing medicine or performing surgery. But choral conductor-teachers should keep the presence of such complexity in mind. Otherwise, simplistic impressions may ensue. Such initial impressions can be difficult to unlearn later. Purposes of the Larynx Singers sometimes presume the sole purpose of the larynx is voice related, i.e., to facilitate speech and song. Yet the larynx serves several functions in the human body. Primary among them is survival. Recall that the larynx is positioned atop the trachea (the windpipe that provides a pathway for air entering and exiting the lungs). Recall also that the larynx lies adjacent to the esophagus. The esophagus is a pathway for food and liquid (and even post-nasal mucous or drip ) to traverse downward into the stomach. On occasion, moreover, the esophagus serves as the route by which acid or other content from the stomach, e.g., vomit, finds its way upward into the throat. From its strategic location atop the trachea and beside the esophagus, the larynx protects the lungs. As a unit, the larynx functions as a valve to prevent foreign substances from entering the lungs by (a) closing off the tracheal airway and (b) triggering a cough reflex when unwelcome matter starts to invade its territory.

5 5 The larynx also plays a role in maintaining the ecology of delicate lung tissues. It assists in the regulation of lung temperature, humidity, and air pressure. With respect to the latter, for instance, the larynx closes the tracheal airway during such biological actions as swallowing, lifting, childbirth, and defecation. Singers and choral teacher-conductors are rightly curious about the larynx because of its critical role in human speech and song. But the major evolutionary and ongoing biological purpose of the larynx is its function in swallowing, coughing, vomiting, and regulation of lung ecology. As Margaret Clegg (2000) observes, evolution of the modern human larynx as associated with fully upright posture evidently values protection of the airway over sustaining a capacity to vocalize. Structural Scaffolding of the Larynx: Laryngeal Cartilages As a unit, the larynx contains six cartilages that provide structural support for its various operations. Cartilage is a type of tough, yet semi-flexible, skeletal tissue. It is softer than bone, but harder than ligament. There are three paired and three unpaired cartilages in the larynx. The epiglottis, thyroid, and cricoid cartilages are unpaired, that is, single entitites. The arytenoids, corniculates, and cuneiforms are paired, meaning there are two of each. The epiglottis is comprised of elastic cartilage that does not ossify, or harden, with age. Generally speaking, all other laryngeal cartilages are comprised largely of hyaline cartilage, which does ossify with age, thus eventually limiting some laryngeal flexibility in older persons. Take time now to master the names and relative locations of these laryngeal cartilages. See Figure 3.3. Just as these cartilages provide scaffolding for the larynx, so can they afford conceptual scaffolding to facilitate subsequent learning about how human voices work.

6 6 Figure 3.3 Anterior and posterior views of the laryngeal cartilages. From Stemple, Glaze & Klaban (2000). Clinical voice pathology. Singular Publishing Group. Permission pending.

7 7 Thyroid Cartilage Unpaired Laryngeal Cartilages The thyroid cartilage is the largest of the laryngeal cartilages. It looks roughly like a crescent shield. Sometimes it is compared to a visor of the sort found on the helmet of a Medieval Knight, because it somewhat resembles that kind of visor in both appearance and movement. The thyroid cartilage consists primarily of two plates (called laminae), a top-center anterior notch, and two projections on either side (See Figure 3.3). The upward rising part of each projection is called a superior cornu. The descending part of each projection is known as an inferior cornu. The inferior cornua join to the cricoid cartilage. The superior cornua connect with ligaments to the hyoid bone. The thyroid cartilage is open in the back. Figure 3.3. The thyroid cartilage (a) anterior-sagittal view and (b) various views. The anterior (front) joining of the laminae forms an angle. Males in puberty and beyond typically display smaller angles than women or pre-pubertal children, resulting in a larger prominence at the point where the laminae join. This laryngeal prominence, especially evident in skinny or thin-necked persons, is referred to colloquially as the Adam s apple.

8 8 Put your finger on your throat and touch this comparatively large protrusion. This maneuver, aside from its value in locating the anterior thyroid cartilage, also affords a convenient way to locate the relative anterior position of the vocal folds. The vocal folds attach anteriorily (at the apex of their V configuration) on the inside of the thyroid cartilage, at a point known as the anterior commissure. See Figure 3.4. Anterior commissure Anterior commissure Figure 3.4. Anterior attachment of vocal folds to the thyroid cartilage at the anterior commissure, superior views. Cricoid Cartilage The cricoid (pronounced CRY-koyd) cartilage lies just beneath the thyroid cartilage. It forms a ring fully surrounding the laryngeal airway. It makes sense to think of the cricoid cartilage as the uppermost ring of the trachea (windpipe). The cricoid ring, however, is wide and tall in the back, lending it a signet ring appearance (See Figure 3.5). Anteriorily (at the front), the cricoid can move upward toward the thyroid cartilage in response to rotation of the cricothyroid joint (formed by the attachment of the cricoid cartilage to the inferior cornu of the thyroid cartilage). Posteriorily (at the back), the cricoid cartilage attaches to the arytenoid cartilages.

9 9 Figure 3.5. Cricoid cartilage, anterior view. Epiglottis The uppermost laryngeal cartilage is the epiglottis. It resembles a shoehorn or a long leaf. See Figure 3.6. The base of the epiglottis is attached to the inside, anterior (front) rim of the thyroid cartilage, just below the thyroid notch. The elasticity of the epiglottis (recall that it does not harden with age) permits it both (a) to fold along its midline and (b) to move forward to close or seal off the laryngeal airway as it is pushed backwards by the tongue. By such movement the epiglottis diverts food and liquid toward the esophagus during swallowing. The epiglottis also triggers a cough reflex to repel foreign particles that may come in contact with it in its sealing position. When the tracheal airway is open, the epiglottis may function as an acoustic resonator. Figure 3.6. Epiglottis, anterior and sagittal views. Paired Laryngeal Cartilages Three laryngeal cartilages are paired. That is, they are present in groups of two. Figure 3.7 illustrates these paired cartilages: the arytenoids, the corniculates, and the cuneiforms.

10 10 Figure 3.7. Paired laryngeal cartilages. Arytenoid Cartilages The arytenoid (pronounced ah-rih-teh-noid) cartilages are positioned atop the posterior (or signet ) portion of the cricoid cartilage (Review Figure 3.3, posterior view, once more). They connect to the cricoid cartilage via the cricoarytenoid joints. Each of the three-sided, pyramidshaped arytenoid cartilages has four surfaces: anterior, lateral, medial, and a base. The arytenoid cartilages can move rather rapidly on two planes: (a) sideways, or laterally, to and from a midline point; and also (b) back to front, with a posterior to anterior movement. To achieve these directional movements, the two arytenoid cartilages can rotate, tilt, and glide in synchronous choreography. Such movements are important, because the vocal folds connect posteriorily (at the wings of their V shape) to the arytenoid cartilages. This point of connection, on the anterior angle at the base of each arytenoid cartilage, is known as the vocal process. When the arytenoids move, they play major roles in abducting (moving apart or separating) and adducting (bringing together) the vocal folds. The arytenoids, in other words, function as opener (abductor) and closer (adductor) cartilages. In performing these functions, the arytenoids facilitate vocal fold motion and also produce changes in the shape of the vocal fold edges. You will need to know the terms abduction and adduction. Alas, these words both look and sound similar. A helpful way to remember their meanings is by reference to their prefixes, aband ad-. In Latin, ab denotes away from (think abstain), while ad means to or toward (think additive).

11 11 Corniculate Cartilages The corniculate (pronounced cornihcueluht) cartilages are situated immediately above and joined to the superior tips of the arytenoid cartilages. The corniculates, along with the superior tips of the arytenoids, form posteriorward horns or cornua, hence their name. (Review again Figure 3.3, posterior view). Cuneiform Cartilages The cuneiform (pronounced CUEnihform) cartilages are embedded in the muscle of the aryepoglottic fold parallel to the epiglottis and just above, but separated from, the corniculate cartilages. You need not bother with them. These tiny, rod-like cartilages simply support the soft tissues of the aryepiglottic folds, which connect the arytenoid cartilages to the epiglottis. Otherwise, they appear to serve no known function from the standpoint of speech and singing. Larynx, Pharynx, Piriform Sinuses, Aryepiglottic Folds The terms larynx and pharynx (pronounced FAIR-inks) sound alike. As we have learned, the larynx houses and protects the vocal folds. Its cartilages form a somewhat flexible tube, about one to two centimeters in length, which connects the respiratory system to the throat area directly above the larynx. This throat area is the pharynx. The pharynx, as the term is typically employed, denotes that area extending from the top of the larynx all the way up to the velum, or soft palate, in the roof of the mouth. This combined throat and mouth area comprises what is commonly called the vocal tract. However, the bottom part of the pharynx also partially surrounds the upper laryngeal tube or epilarynx area. In this bottom part of the pharynx, moreover, there are two cavities, one on the front right side of the laryngeal tube and one on the front left side, known as the piriform sinuses or recesses. These pear-shaped cavities (Figure 3.8, Figure 3.9), located to the rear of the arytenoids and laterally to the aryepiglottic folds (which separate these cavities from the larynx), contain openings to the esophagus (the pathway tube to and from the stomach). Food and liquid pass through these openings.

12 12 Piriform sinuses Figure 3.8. Anterior wall of the pharynx viewed from behind. The pharynx communicates with the nasal cavity, auditory tubes, oral cavity, larynx and esophagus. Figure 3.9. Piriform sinuses and aryepiglottic fold viewed from above.