17. Notes on the Anatomy and Physiology of the Vocal Tract

Respiration7?

The process of respiration involves two actions, inhalation and exhala­tion. Air is inhaled and exhaled through the nose or nasal cavities, or through the pharynx, the larynx, the trachea or windpipe, the lung passages, and in and out of the lungs.

In quiet breathing the nasal cavity is open. The oral cavity may be open or closed. The nasopharynx, oropharynx, and the laryngopharynx make up a tubelike cavity, except when air is inhaled or exhaled through the mouth alone. In this type of breathing the nasopharynx is eliminated as one of the air passages.   During swallowing breathing is inhibited.

The laryngeal cavity is open, with the folds retracted for unobstructed breathing. The trachea or windpipe, a tube about a half an inch in diameter and four and a half inches long, is open for unobstructed breathing. The lungs fill on inhalation, and empty on exhalation, through a decrease in the dimensions of the thorax or chest cavity.

In normal vegetative breathing, the minimum necessary to maintain life, respiration is a rhythmical process occurring fifteen to eighteen times per minute. The time of each inhalation and exhalation is about equal, although the time may vary due to emotional disturbances, muscular effort, and fatigue. Normal breathing is an automatic or unconscious process, and has been termed passive or quiet breathing.

The breathing process, however, responds to conscious control. This occurs in singing or speech, where the timing changes to a quick inhalation, and to a slow controlled exhalation. This has been termed active breathing. As it becomes established by habit, active breathing becomes an automatic action, and unconsciously controlled. Then it may be said to be natural breathing.

The Thorax or Chest-cage7e

The thorax or chest-cage is a closed cavity, made up of a skeleton of bones and cartilages. It is bounded by the sternum or breastbone and coastal or rib cartilages in front; the twelve rib cartilages (costae) on each side; the twelve thoracic vertebrae and posterior parts of the ribs behind; and the diaphragm, a sheath of muscle on the bottom which is pushed upward in the shape of a dome by the viscera from below.

The sternum (breastbone) forms the central part of the front of the thor­acic wall. At the top it supports the clavicles (collarbones), and its edges or margins articulate with the cartilages of the ribs, 1 to 7. The average length of the sternum is 17 cm. (6.8 inches).

At birth the ribs are at right angles to the axis of the body. They grad­ually curve or change their angle, until at the age of four years the angle has changed from 90 degrees to approximately82 degrees, and in the adult to an angle of approximately 62 degrees. This makes for more efficient breathing. When the angle of the ribs is 90 degrees or slightly less, a baby must breathe in a predominantly abdominal manner. The suggestion to breathe like a baby is actually a suggestion to breathe abdominally. The suggestion to breathe as when lying down is conducive to breathing abdominally, since intercostal or rib breathing requires more effort than is necessary for quiet breathing.

The thorax or chest-cage has three diameters: vertical or length, trans­verse or width, and anteroposterior or depth. The cavity enclosed has the shape of a truncated cone, with its base at the bottom, and its apex at the top.   All diameters are increased during respiration.

The first seven ribs on each side are attached in front to the breastbone and in the back to the vertebrae. The next three ribs on each side are at­tached to the vertebrae in the back, and to the seventh rib above. The re­maining two ribs, called the floating ribs, are attached to the tenth rib above. The internal and external rib muscles bridge the eleven intercostal spaces, and move some or all of the cartilages and ribs during respiration.

The greatest expansion or movement of the thorax or chest-cage and the muscles for its control is possible below the first seven ribs, and explains why deep breathing and breath control should center in this region - below the breastbone and above the waistline.

The Trachea or Windpipe79

The trachea or windpipe is a cartilaginous and membranous tube, which extends from below the vocal folds to the division into the two bronchi (tubes), which lead to the lungs. In men, the length of the windpipe is on an average 11.5 cm. (4.53 inches); in women it is about 10 cm. (4 inches).

The trachea is made up of approximately eighteen cartilages, each of which forms two-thirds of a ring, the remaining one third being completed by fibro-elastic tissue and smooth muscle fibers. This construction permits the trachea to move inward when food passes down the esophagus behind.

The construction of the trachea also makes possible maximum distension during forced respiration. The trachealis muscle relaxes on inhalation, and the cross-sectional area of the windpipe becomes greater; on forced exhala­tion as in singing, the trachealis muscle contracts, thereby decreasing the cross-sectional area.

Bifurcation 80

The trachea divides itself into two branches called bronchi (bronchial tubes). This division is called bifurcation. The cross-sectional area is then changed, and the combined area of the bronchi exceeds that of the trachea. With each division and subdivision, bronchi into bronchioles, bronchioles into respiratory broncholes, into alveolar ducts, into alveolar sacs, there is a constantly increasing cross-sectional area of the pulmonary tree leading into the lungs. Along with this is a constantly decreasing resistance to the air entering the trachea.   This keeps the vocal cords open and retracted.

On exhalation there is a constantly decreasing cross-sectional area in the bronchial tubes, with a constantly increasing resistance to the air. This tends to approximate the vocal cords.

This is significant in a study of forced breathing necessary to vocal pro­duction. The contraction of the abdominal muscles establishes what is called the abdominal press, resulting in a pressure flow of the breath which not only vibrates the vocal cords, but can also assist in approximating them and holding them in approximation. This pressure flow of the breath, when pro­perly established, relieves the pharynx or throat of undue tension, and leaves the articulatory mechanism free and flexible.

The Lungs81

As previously mentioned, the trachea divides itself at the bifurcation or forking point into two bronchial tubes, each of which leads to a lung. The right lung is divided into three lobes; the left lung into only two lobes to make room for the heart.

The lungs are of a light, porous, highly elastic material. They always completely fill the thoracic cavity. Any change in the volume of the thoracic cavity is immediately reflected in the volume of the lungs. Any increase in the size of the thorax results in an active inhalation; any decrease in its size results in a passive exhalation.   Passive means "without effort."

The lungs are conical in shape. They are suspended freely in and norm­ally occupy the entire thorax. They are attached only at the top of the thorax where the bronchi or air tubes and the pulmonary arteries enter.

Each lung has a broad base resting on the diaphragm.

Each lung is covered by a delicate membrane called the pleura. The space between the pleura and the walls of the thorax contains a small amount of watery fluid by which the respiratory movements are rendered frictionless. Inflammation of the pleura is called pleurisy.

The lungs are said to play a purely passive role in respiratory move­ments. The changes they undergo are due directly to changes in the capacity of the thoracic cavity.

The Mechanism of Inhalation82

Inhalation may be produced by two methods: 1. by a contraction of the diaphragm, and 2. by an elevation of the ribs.

The Diaphragm83

The diaphragm is the most important muscle of inhalation. It is a mus­cular-tendonous partition which separates the thoracic viscera from the ab­dominal viscera. Its muscle fibers are attached in front to the sternum or breastbone, in the back to the spinal column, and on the sides to the lower ribs, and then in the center to the central tendon, a large, flat, thin, oval-shaped band of tissue.

The control of the diaphragm in passive or normal breathing lies in the medulla oblongata, the division of the brain which includes the respiratory center. As a result of impulses from this center, the diaphragm contracts downward and outward, forcing the abdominal contents downward and out­ward.   When the limits of the elasticity of the abdominal wall have been reached, the descent of the abdominal contents or viscera is stopped. The viscera now act as a fulcrum for the central tendon, and any further con­traction of the muscle fibers will cause the diaphragm to push the lower ribs outward. As a result the dimensions of the thoracic cavity are increased vertically, transversally, and antero-posteriorally.

As the diaphragm descends, its dome-shape seems to change very little. It would seem to move up and down like a piston, peeling off the thoracic boundary, while the base of the lungs expands to fill the space. In quiet breathing, the range of its movement is 3.0 cm. or a little over an inch.

Intercostal (rib) Breathing 84

The muscles utilized in quiet inhalation in addition to the diaphragm, are the external intercostals, the scaleni (triangular muscles), and the leva-tores costarum, the muscles that elevate the ribs. In active breathing as is used in singing or speech, several additional muscles maybe used: the ser-ratus muscles (notched or edged like a saw), and pectoralis (chest muscles shaped like a crows beak) the lattissimus dorsi (back muscles like lath-work pattern), the subclavious muscle (under the clavicle), and the sterno-cleido mastoid (muscle attached to the sternum).

In active breathing, the greater part of the breath inhaled can be attri­buted to the action of the diaphragm, the smaller part to the action of the intercostal muscles.88

The Mechanism of Exhalation86

Exhalation is the result of a decrease in the size of the thoracic cavity or chest cage. There are two ways that this may be accomplished: 1. by forcing the diaphragm back into the thoracic cavity; and 2. by depressing the ribs.

The first is accomplished by a contraction of the abdominal muscles87-the erectus, the external and internal oblique, and the transversus. This action is called the abdominal press. It raises the pressure in the abdom­inal cavity under the diaphragm, thereby pushing it back up into the thorax, and reducing the volume of the thoracic cavity and hence of the lungs. This is what happens when the breath is allowed to escape through an open glottis. If no breath is allowed to escape and the glottis is closed, the abdominal pressure will be felt mainly in the pelvic organs. This low abdominal pres­sure is the moving force in micuration (urination), defecation (evacuation of the bowels), and parturition (child birth). It should not be confused with the high abdominal pressure necessary to establish a pressure flow of the breath to not only vibrate the vocal cords, but to assist in approximating them as well, for singing as well as for speech.

It maybe argued that the abdominal musculature operates as one muscle. Pneumograph studies of the breathing of singers showed that in good singing there was practically no movement of the lower abdominal musculature on inhalation or exhalation, and that on exhalation the emphasis was on pressure exerted at a higher level.

A decrease in the size of the thoracic cavity may also be accomplished by depressing the ribs. The following muscles are involved: the internal intercostals (intercostales), the triangular sternum (triangularis sterni), and the transverse thoracic (transversis thoracis). The greater the expan­sion of the ribcage, the greater the transverse and anterio-posterior dia­meters of the thorax and the greater the inhalation. The greater the inhala­tion, the further the ribcage has to fall, and the greater the breath support. At the end of the inhalation phase, the intercostal muscles and the diaphragm relax.

In quiet breathing, certain passive factors assist the abdominal and intercostal muscles in the process of exhalation. These factors include 1. Gravity. The weight of the chest-cage will cause it to come down upon relaxation of the intercostal muscles of inhalation; 2. the elastic recoil of the lung tissue as the air is expelled; 3. the elastic recoil of the viscera; and the relaxed diaphragm, which is pushed upward by the viscera, and also drawn up by the negative intrathoracic pressure.

Whereas in passive or quiet exhalation there is a minimum of action by the muscles of exhalation, in forced exhalation they become predominant over the passive factors. If a fine control of the breath is to be established, there must be a delay in the return of the passive factors to their normal positions. The passive factors also contribute to a more forceful exhalation if there is a greater movement on inhalation. For example, greater expan­sion of the highly elastic lung tissue in inhalation re suits in a stronger recoil.

Although both inhalation and exhalation are essentially involuntary actions, they nevertheless can be under voluntary control to a certain extent. When involuntary, they are under the control of the medulla oblongata; when vol­untary, they are under the control of the cerebral cortex.

The ability of man to shift from one control to another, makes possible the use of conscious or voluntary actions in the learning process, which later become unconscious or involuntary actions.

The Larynx 88

The cartilaginous framework of the larynx is made up of the following cartilages: 1. the cricoid or ring cartilage; 2. the thyroid or shield cartilage; 3. the two arytenoid or pyramid cartilages; 4. the two corniculate (corn-shaped) cartilages forming the apex of the arytenoid cartilages; 5. the two cuneiform or small elongated rods lying in the arytenoid folds of the larynx; and 6. the epiglottis, shaped like a leaf with its stalk pointed downward, and attached to the angle of the thyroid cartilage.

1. The cricoid or signet ring cartilage is located at the top of the wind­ pipe, and is the articulating foundation of the laryngeal framework. It provides places of attachment for the posterior cricoarytenoid muscles, for some of the fibers of the inferior constrictor muscle, and for the lateral cricothyroid muscle.   The band of the ring provides places of origin at the front and sides for the cricothyroid muscles. On the top of the cartilage and at the sides are two oval surfaces on which the arytenoid cartilages rest.
   
2. The thyroid cartilage makes up the front and side walls of the frame­ work of the larynx. It is shield shaped, the angle where the sides meet being 90 to 100 degrees in the male, and 120 to 130 degrees in the female adult or the child. The vocal cords are attached to the inside of the thyroid cartilage at the angle where the sides meet, with one on each side of the midline. The inner surface also provides places of attachment for the epiglottis, and the thyroarytenoid and the cricothyroid muscles.
   
3. The arytenoid cartilages, pyramid in shape, are set at the back and on top of the cricoid cartilages.   Each arytenoid cartilage has a triangular base which articulates  with the cricoid cartilage, and each has three surfaces, separated by three borders - front, back, and side. The surfaces of each cartilage provide places of attachment behind for the posterior cricoarytenoid muscle, and in front to the lateral cricoarytenoid; in front to the lateral thyroarytenoid muscle and to the thyroarytenoid ligament.  The oblique and transverse arytenoid muscles have their attachment in the smooth and posterior surfaces of the arytenoid cartilages.
4. The corniculate (corn-shaped) cartilages are roughly pyramidal and articulate with the apex of each arytenoid cartilage. For phonation, the cartilaginous part of the glottis between the arytenoids must be closed, so that the air current can be directed through the membranous part of the glottis. The corniculates assist in making the closure complete.
5. The cuneiform (wedge-shaped) cartilages are likewise situated in the arytenoidepiglottic folds. Each is anterior and lateral of its respective arytenoid cartilage, and assists in making the closure of the glottis complete.
6. The epiglottis, shaped like a leaf with its stalk pointed downward, is attached to the inner surface of the angle of the thyroid cartilage by means of the thyroepiglottis ligament.   The upper leaf-like part is free and curves up behind the base of the tongue.   Most of the base of the tongue overhangs the epiglottis.   Except for the portion just below the center, the epiglottis presents a concave surface toward the laryngeal cavity. The portion excepted is a slight eminence called the cushion or tubercle of the epiglottis.

The Intrinsic Muscles of the Larynx89

1.         Cricothyroid:   (ring-shield muscles)

Action:  Cause the cricoid cartilage to rotate and slide on the thyroid cartilage, thereby increasing the length of the glottis.

2.         Posterior cricoarytenoid:   (ring-pyramid muscles)

Action:  Assist in opening (abduction) the glottis or in tensing the vocal cords.

3.         Lateral cricoarytenoid:   (side ring-pyramid muscles)

Action:   Bring about an approximation of the vocal cords and assist in tensing them.

4.         Oblique arytenoid:   (slanting-pyramid muscles)

Action:   Part of the sphincter group of muscles which have the function of closing (abduction) the cartilaginous glottis.

5.         Transverse arytenoid:   (crosswise-pyramid muscles)

Action: Part of the sphincter groups. Assist in tensing the vocal folds.

6.         Thyroarytenoid:   (shield-pyramid muscles)

Action:   Part of the sphincter group.   Relax the vocal folds.

The Vocal Cords (Folds)90

The vocal cords or folds are the edges of the thyroarytenoid muscles. They are composed of elastic muscular folds which can be drawn together (approximated) and tensed, thereby setting up a resistance to the expired breath.   The result is a series of puffs that are resolved into musical tone.

When the cords are retracted, the laryngeal cavity is an open tube which leads into the pharynx. When they are approximated, they divide the laryn­geal cavity into two parts. The part above is called the vestibule, or hyper-glottal cavity; the part below, the sub-vestibule, or hypoglottal cavity .

The vestibule contains the ventricular folds, sometimes called the false vocal cords, which can completely close over the true vocal cords. In so doing they act as a protective device which prevents the entrance of foreign substances into the lungs. Their partial contraction is thought to be one of the causes of poor vocal quality. Like the vocal cords, the ventricular folds are attached in front to the inside of the thyroid cartilage, and at the back to the arytenoid cartilages. In some persons they may act as secondary vocal folds, and approximate above the true vocal folds to produce secondary vocal tone of their own called double voice.90

The Process of Phonation91

Phonation is the act or process of generating vocal sound. W It is the result of a pressure flow of the breath which is built up beneath the vocal lips. When the force of the pressure is sufficient to blow the vocal lips apart, puffs of air are released which produce sound waves.

After each puff of air, the vocal lips snap back into their approximation. With continued pressure flow of the breath there are repeated openings and closings of the vocal lips, the rapidity of which depends upon the breath pressure and the degree of contraction of the laryngeal muscles. The pitch of the sound produced is determined by the number of vibrations of the vocal lips per second. A pitch of middle C or 256 vibrations per second means that there must be 256 vibrations of the vocal lips per second. The sound waves generated consist of a fundamental and a rich supply of overtones. This is essentially the harmonic or relative pitch theory of vowel production.

The vocal cords are the source of the greatest amount of acoustical energy. As viewed in the Bell Telephone film "High Speed Motion Pictures of the Vocal Cords," the vocal cords vibrate much as the lips of a bugler or the lips of one giving a bronx cheer. Motion pictures taken with an exact duplicate of the Bell Telephone equipment were limited however to pictures of the vocal cords producing one sound (eh) , and one loudness (piano).

Different vowel sounds and different degrees of loudness brought about changes in the position of the epiglottis, which prevented unobstructed views for photographing the actions of the vocal cords. One is apt to come to the conclusion that the vocal cords vibrate in the same way for all vowel sounds. This would lead to the conclusion that the vocal cords are only a pitch mech­anism.

Motion pictures taken with Russell's laryngo-periskop indicated that "the laryngeal cavity prepares for the production of each vowel sound by assuming such a variation of form in conjunction with the vocal cords, as will result in producing not only the note to be intoned, but also a particular selection of overtones or partials. "42 This leads to the conclusion that the sets or vowel forms in the oral and nasopharynx regions are reflected into the laryngeal cavity. It is then possible to consider phonation as a part of the enunciation of the vowel sounds.

If we consider voice production in singing a matter of tuning the resona­tors - mouth, pharynx, and nasal passages - to the generator - the larynx -then the tuning process must necessarily be based on the vowel sounds, since they are the basis for vocal sound. The result of the tuning must sound free. This calls for noninterference from the extrinsic muscles, such as undue tightness of the jaw, palate and tongue, which will be reflected in the action of the vocal lips and prevent their unhindered vibration.

Freedom then is basically a freedom from the interference of any factors that prevent an unhindered vibration of the vocal cords for the desired qua­lity, pitch, duration, and intensity of the tone desired.

Registration and Range (see chapter 3)

The Falsetto Mechanism92

In falsetto the more external fibers of the thyroarytenoid muscles are relaxed. The more internal fibers of the thyroarytenoid muscles are tensed. The anteroposterior diameter of the glottis is increased slightly by the ten­sion of the posterior cricoarytenoid and cricothyroid muscles. The glottal lips are blown apart by the air pressure in the form of a small elliptical opening in the middle or anterior one-third of the length of the vocal folds. This results in a constant escape of air.

With proper dampening of the cords, the elliptical opening of the cords can be straightened out, and the amount of breath lost can be cut down. The result is a tone quality that seems to be a continuation of the quality of the lower registers. This may be called the high-voice mechanism, in contrast to the falsetto mechanism. The dynamic control of the tone quality of the high voice mechanism, as well as the control of the so-called messa di voce - swelling a tone from piano to forte and back to piano - is more dependent on air pressure than on the increased elasticity of the vocal folds.

The basis for dampening the posterior parts of the vocal folds lies in the co-ordinated tensions in the larynx as reflected in normal tone quality. In order to make the change to the high-voice mechanism, these tensions, which seem like one tension, must be held, and a change made in resonance placement. This is a change to a stronger mouth resonance, which is the basis of falsetto in the high voice. A psychological suggestion is: "Approach your high notes as if you were going to sing them ‘open’, and modify your sounds to a stronger mouth resonance."

Primary enunciation of the vowel sounds may be said to take place at the level of the larynx, and secondary enunciation at the level of the mouth. The emphasis in the dampened falsetto should be on a primary enunciation of the vowel sounds at the level of the larynx, controlled dynamically by a pressure flow of the breath.   This is also true in the female high voice.

The Articulatory Mechanism The Region of the Mouth Cavity "

The inner mouth cavity is bounded at the front and sides by the teeth and gums; in the back by the opening into the pharynx; at the top of roof by mucous membrane, a large portion of the tongue, and the mylohyoid (jaw-hyoid) and the geniohyoid (chin-hyoid) muscles.

The outer mouth cavity is bounded by the lips and cheeks in front, and by the teeth and gums on the inside. It opens upon the surface of the face at the mouth.

The upper jaw is made up of two fused bones (maxillae), each consisting of a body and four processes - alveolar, frontal, palatine, and zygomatic. The palatine process makes up most of the roof of the mouth and the floor of the nose.

The lower jaw consists of a horse shoe-shaped bone - the mandible -with perpendicular framework, and is joined with the two temporal (temple) bones.

The permanent teeth include: 4 incisors (cutters), 2 canines (eye teeth), 4 premolars (bicuspids), and 6 molars (grinders) in each jaw - a total of 32 teeth in all.

The salivary glands include three large pairs - theparotid (below and in front of each ear), the submaxillary (inside the lower jaw), and the sub-lingual (under the tongue) - which pour their secretions into the cavity of the mouth.

The Lips94

The lips, the muscular folds bounding the front opening of the mouth, are composed of skin, superficial fascia (surface tissue), the orbicularis muscle and other muscles inserted around it, alveolar tissue and mucous membrane. Each lip is connected in the median line to its respective gum by what is called the frenulum, a fold of mucous membrane.

The lips can assume three different basic positions: lateral, puckered, or relaxed.  Each position can affect the resonance quality of the tone sung.

The Cheeks 95

The cheeks (buccae) make up the sides of the face. Their composition from the outer surface to the inner is as follows: skin, superficial fascia (surface tissue), the cheek muscle (buccinator muscle), the submucous (underlying) alveolar tissue, and mucous membrane.

The attachment of the cheek (buccinator) muscles to the superior con­strictor of the pharynx at the wing of the lower jaw bone union makes pos­sible the continuity of the lateral walls of the oral cavity with the lateral walls of the pharynx.

Muscles of the Mouth Region 96

1.    Quadratus labii superioris (flat,  roughly squared muscle at each side of the upper lip and nose).

Action:  Deepens furrow between upper lip and nose, and widens nostril.

The above muscle has three heads:

1. Caput angulare (base of lower jaw). Action:   Raises upper lip.
2. Caput infraorbitale(bone cavity in head below the orbit in which the eye is located).

Action:   Lifts and protrudes upper lip.

3.         Caput zygomaticum (head-zygomatic arch)

Action:   Draws upper lip backward, upward, and outward.

1. Caninus (dog-like muscle) Action:   Raises angle of mouth.
   
2. Zygomaticus (shaped like a yoke).
   

Action:  Draws angle of mouth upward and backward as in laughing.

4.         Buccinator (cheek muscles): thin, broad muscles forming the wall of the cheek.

Action:   Compress the cheeks and retract the angles of the mouth.

5.         Risorius (laughing muscles): a narrow band of muscle fibers arising from the facia.

Action:   Draws angle of mouth out; compresses the cheek.

6.         Orbicular is oris (shaped like a circle):   the sphincter of the buccal (mouth) opening.

Action:   Closes lips; protrudes lips; draws upper lip down; draws lower lip up; draws corners of the mouth together; draws lips back against the teeth.

It is questionable as to whether this muscle is a separate entity or made up of other muscles, to include the caninus, zygomaticus, buccinator, caput longum of triangularis, the quadrarus labii superior and inferior, and the orbicularis oris.

7. Triangularis (shape of a triangle) Action:   Pulls down corners of the mouth.
   
8. Quadratus labii inferiors (flat roughly squared muscle in each side of lower lip).
   

Action:  Draws lower lip down and lateral ward.

9.         Mentalis (chin muscle)

Action:  Protrudes lower lip and wrinkles skin of chin. 10.     Platysma (flat thin layer of muscle)

Action:  Depresses lower lip and moves it laterally.

The Muscles of Mastication97

1.         Masseter (chewing muscles).   Either of a pair of large muscles which raise the lower jaw in chewing.

Action: Raise mandible - lower jaw - against maxillae -upper jaw-bone.

2.         Temporalis (temple muscles)

Action: Raise mandible against maxillae; posterior fibers retract man­dible, that is, draws mandible in posterior direction.

3.         External pterygoid (like a wing)

Action:  Raises and draws lower jaw forward.

4.    Internal pterygoid (like a wing)

Action:   Raises and draws lower jaw forward.

The Tongue 98

The tongue (lingua) lies on the floor of the mouth, with its root or base (radix linguae) directed backward. The tongue has four attachments: 1. to the soft palate by the tongue-palate (glossopalatine) arches; 2. to the pharynx by the superior constrictors (muscles that constrict, contract); 3. to the hyoid bone, by the hyoglossal muscles (flat muscles on either side of the tongue connecting with the body and greater horn of the hyoid bone); 4. to the epiglottis by the glossoepiglottic folds, a thin lamellae (layer) of yellow car-tilate which projects upward behind the tongue and just in front of the tongue glottis.

The tip (apex) of the tongue is directed forward against the inside of the lower teeth. The upper surface (dorsum)of the tongue is convex, and is div­ided lengthwise by a middle groove (sulcus). The rear or posterior one third of the back of the tongue moves downward in front of the pharynx and overhangs the epiglottis. The under surface of the tongue is connected by the chin-tongue (genio-glossus muscle) to the lower jaw (mandible). The frenulum, a fold of mucous membrane which lines the undersurface of the tongue, connects the tongue to the floor of the mouth.

There are extrinsic and intrinsic muscles in either half of the tongue. By extrinsic is meant, muscles which have their origins outside the tongue; by intrinsic is meant, muscles which have their origins entirely within it. The extrinsic muscles bring about changes in the position of the mass of the tongue and changes in form. The intrinsic muscles affect only the form of the tongue.

The Hyoid Bone99

The hyoid or lingual (tongue) bone is horseshoe-shaped, with its open end directed posteriorly. It is situated between the larynx and the tongue, and serves as a place of attachment for the muscles of the tongue. All move­ments or changes in the position of the hyoid bone are reflected in move­ments of the larynx, which is suspended from the hyoid bone. The front surface of the bone is convex; the back surface is concave, corresponding to the shape of the epiglottis.

Due to the fact that the hyoid bone is not directly attached to any other part of the skeletal framework of the body, it is free to move in any direct­ion - up, down, forward, backward, to the left or right, or in any combina­tion of these directions. Such freedom of movement makes the hyoid bone an important factor in vocal production.

The hyoid bone has, however, muscular attachments to other structures: to the larynx, lower jaw, tongue, cheek bones, pharynx sternum, and to the sternum. Its movements and the movements of these structures influence each other.

The Extrinsic Muscles of the Tongue100

1.         Genioglossus (chin and tongue muscles)

Action: Protrude or retract the tongue. All fibers, lower and higher, together depress the tongue and groove the dorsum.

2.         Hyoglossus (hyoid bone and tongue muscle)

Action:  Depresses side of tongue; draws it back when protruded.

3.         Styloglossus (pointed-tongue muscles)

Action: Raise the back of the tongue toward the roof of the mouth. When protruded the muscles draw it back into the mouth.

4.         Glossopalatinus (tongue-palate muscle)

Action: Lifts back of tongue; draws sides of soft palate down, constrict­ing isthmus of the fauces. This prevents food from returning to the mouth after swallowing.

The Intrinsic Muscles of the Tongue icn

1. Longitudinous superior (long muscle above) Action:  Shortens tongue and makes it wider.
   
2. Longitudinous inferior (long muscle below)
   

Action: Shortens tongue and makes it wider; pulls apex downward, makes dorsum convex.

3.         Transverse linguae (crosswise-tongue muscle)

Action:   Lengthens, narrows, and thickens tongue; lifts its edges.

4.         Verticalis linguae (vertical tongue muscle) Action:   Widens and flattens tip of tongue.

The tongue has extraordinary flexibility. As a result, most speech sounds can be made in an infinite number of ways, and much of the control of these sounds is due to the ear. This is the result of many years of con­ditioning.

The Palate102

The roof of the mouth is made up of two parts - the bony or hard palate, and the soft palate. The hard palate is covered with fibrous tissue and mucous membrane, and is limited in front and on the sides by the gums, (gingivae). Behind it and continuous with the hard palate is the soft palate, a fold of muscular and fibrous, sheet-like tissue covered with mucous membrane. The soft palate is continuous on the sides with the pharynx.

The lower part of the soft palate, hanging like a curtain between the mouth and the pharynx, is called the velum. A small, fleshy, more or less rounded protuberance called the uvula (grape-shaped), hangs from the middle of the velum. The uvula may be considered as a resonance coupler between the mouth and the nasal passages.

The fauces (isthmus faucium) are openings on each side of the throat by means of which the mouth cavity and the pharynx are connected. They are bounded on the top by the soft palate, and on the sides by the glossopalatine arch, (tongue-palate) and below by the tongue.

The glossopalatine arch of the fauces is due to the bulge of the glosso-palatine muscle, and forms the front pillar of the fauces. The pharyngopala-tine (pharynx-palate) arch is due to the bulge of the pharyngopalatine muscle, with its covering mucous membrane, and formsthe rear pillar of the fauces.

The soft palate makes possible a closure between the nasal and the oral cavities during the production of all English sounds except the nasals - (m), (n), and (ng). X-ray pictures of many of the leading singers of the Metro­politan Opera taken by G. Oscar Russell21proved that in their singing the nasal passages were closed off by the soft palate, except on the nasals. In testing a group of trained singers, Warren Wooldridge23found that a jury of teachers of singing could not distinguish any difference in the quality of a vowel sound sung with the nasal passages plugged or unplugged. This would prove that in what is accepted as good tone quality in singing, the nasal pas­sages are not used as resonators.

Other research studies by Kaltenborn12 prove that nasality caused by breath passing through the nose can be avoided by using a proportionately greater mouth opening than the opening into the nose. As previously men­tioned, Bartholomew and Russell are of the opinion that in good singing there is no resonance above the level of the mouth, except on the nasals.

The question: "Will the removal of my tonsils affect my singing voice?" can be answered by the knowledge that the fauces and the pillars of the fauces are actually musculature, which if cut into may destroy or upset the pharyn-geal control necessary in the act of good singing.

The removal of the uvula, often made necessary because of elongation, eliminates this part of the palate as a coupler to close off the nasal passages. Its loss can be counteracted by a sphincter action of the soft palate.

The Muscles of the Palate 103

1.         Tensor veli palatini (tense veils of soft palate)

Action:   Depress and flatten arch of the soft palate and makes the soft palate tense; open Eustachian tubes during swallowing.

2.         Levator veli palatini (elevator of the palate)

Action: Raises soft palate, increasing arch and bringing soft palate into contact with the posterior wall of the pharynx. Co-ordinated with the contractions of the superior pharyngeal constrictor. When the latter contracts it forms a ridge, called Passavant's ridge, in the posterior pharyngeal wall. Movement of the palate to the ridge results in closing the pharyngeal isthmus.

3.         Glossopalatinous (tongue-palate muscle)

Action: Elevates pharynx and larynx; narrows fauces; depresses soft palate.

4.         Pharyngopalatinous (pharynx-palate muscle)

Action: Elevates pharynx and larynx; narrows fauces; depresses soft palate.

5.         Musculus uvulae (muscle of the uvula) Action:  Elevates uvula.

The Pharyngeal Region'04

The pharynx is a muscular, membranous, cone-like tube, extending from the base of the skull to the level of the cricoid cartilage in front, and to the level of the sixth cervical vertebra in the back. It is about 11 cm or 4.5 inches in length. It opens into the esophagus at the level of the inferior border of the cricoid cartilage.

The pharynx has three divisions: the nasopharynx or nasal part; the oropharynx or mouth part; and the laryngopharynx or laryngeal part.

The nasopharynx lies behind the nose and above the level of the soft pal­ate. In contrast to the oral and laryngopharynx parts of the pharynx, its cavity always remains open. It is connected with the nose through the nasal cavities. On its back wall is a mass of lymphoid tissue (from lymph glands) - the pharyngeal tonsil or adenoids. The nasal passages are separated from each other by the nasal septum.

The laryngopharynx extends from the hyoid bone to the lower edge of the cricoid cartilage where it becomes continuous with the esophagus.

The transverse diameter of the pharynx is greater than its anteroposter-ior diameter. Its widest point is opposite the greater horn of the hyoid bone; its narrowest point is at the junction of the esophagus.

The Muscles of the Pharynx 10°

1.         Superior pharyngeal constrictors (flat, thin muscles which form most of the fleshy walls of the pharynx).

Action:   Contract pharynx in  swallowing.    Constrict top portion  of pharynx.

2. Middle pharyngeal constrictor (as above, flat, thin muscles, etc.) Action:   Contracts pharynx in swallowing.   Constricts lower portion of the pharynx.
   
3. Inferior pharyngeal constrictor (as above, flat, thin muscles, etc.) Action:   Contracts diameter of pharynx.   Constricts lower portion of pharynx.
   
4. Stylopharyngeus (a slender muscle connecting the base of the styloid process and the pharynx).
   

Action:  Raises and dilates pharynx; raises larynx.

5.         Salpinggopharyngeus (pertaining to Eustachian tubes and pharynx) Action:   Narrows fauces; elevates superior portion of the pharynx.

The Nose and the Nasal Sinuses106

The external nose, pyramidal in form, is connected directly with the forehead. It is composed of tendonous fibers from the fascia, and covers the lower part of the nasal bone, and the upper part of the lateral nasal car­tilages.   Its free angle is the apex.

The inside of the nose is a large, general cavity, extending from the floor of the cranium to the roof of the oral cavity. The nasal cavity is div­ided by a middle wall (septum) into two nasal passages (nasal fossae). In front,  the  nasal passages   open into a vestibule,  and  then to the outside through the nostrils (anterior nares). At the back they communicate with the nasal part of the pharynx through funnel-like passages (the choanae or posterior nares).

On the lateral walls of these passages can be seen the nasal turbinates (bones of the nose - superior, middle, and inferior). Above the superior turbinate bone is the sphenoidal sinus. Between the superior and middle turbinates is a nasal passage into whichopens the posterior ethmoidal sinus. Between the middle and inferior turbinates is a nasal passage into which open the middle and anterior ethmoidal sinuses, the frontal sinus, and the maxillary sinus. Below the inferior turbinate is a passage into which opens the nasolacrimal (tear) duct.

The roof of the nasal cavity is made up, from front to back, of parts of the nasal, frontal, ethmoidal, and sphenoidal bones. The front three-fourths of the floor is made up of the palatine process of the maxilla (upper jaw­bone) ; the back one-fourth of the horizontal plate of the palatine bone.

The nasal sinuses are the result of a growing outward of the walls of the nasal cavities. This action increases the size of the facial bones with­out any increase in weight. Although the nasal sinuses are not present at birth, they are complete at puberty or adulthood.

The number of nasal sinuses and their volumes follow:

1. Two frontal sinuses, with a volume of 20 cc each.
   
2. Six ethmoidal air cells or sinuses - three on each side averaging ap­proximately 7. 5 cc. - anterior, middle and posterior ethmoidal sinuses.
   
3. Two sphenoidal sinuses with a combined volume of 20 cc.
   
4. Two maxillary sinuses, with a volume of 25 cc each.
   

The Muscles of the Nose

1.         Procerus (in front-horn muscle)

Action: Draws down the medial angle of the eyebrows, and produces transverse wrinkles over the bridge of the nose.

2.         Nasalis (nose muscle)

Action: Depresses the cartilaginous part of the nose, and draws the ala (wing-like process) of the nose downward.

3.         Depressor septi (depressor-wall muscle)

Action: Antagonist of the other muscles of the nose, drawing the ala (wing) of the nose downward, thereby constricting the aperture of the nares.

4.         Dilator naris posterior (2), (dilator-nares muscles)

Action: Enlarges the aperture of the nares; resists tendency of nostrils to close from atmospheric pressure.

Resonators 107

A resonator in singing maybe definedas a cavity that amplifies or modi­fies vibrations produced by the vocal cords. The extent to which the vibra­tions are amplified or modified will depend not only on the shape and size of the resonator, but on the character of its walls as well. Hard walls reflect, soft walls absorb.

There are basically two types of resonators. One type has a more or less definite period, and because of this will produce only pitches corres­ponding to its fundamental frequency and those in tune with its overtones. The other type, with no particular frequency of its own, responds to com­plex tones of many frequencies, and will produce many different qualities.

The human resonators108 are made up of the following cavities: the bronchi and trachea; the larynx - above and below the glottis; the pharyngeal cavity -to include the laryngo pharynx, oropharynx and the nasopharynx; the nasal passages and the nasal sinuses - maxillary, frontal, sphenoidal, and eth-moidal. The pharynx mouth, and nasal passages are considered to be the most important resonators. Of these, the pharynx is considered to be the primary resonator. It can be coupled with the nose and/or the mouth to form one resonator. How much the other cavities -bronchi, trachea, larynx, and sinuses - modify or amplify the singing tone is a matter of conjecture.

The problem in the teaching of singing is essentially one of tuning the resonators - the pharynx, mouth and nasal passages - to the vibrations of the vocal cords. Whether the resonators respond sympathetically to the vocal cord vibrations, or whether it is a matter of forced vibration, is dif­ficult to determine. It would seem to be a matter of both. When they are properly tuned, that is, when the normal singing quality is established, the voice may be said to be properly placed.

The approximate volumes of the resonators are as follows: bronchi and trachea 60cc, the larynx 25cc, the pharynx 80cc, the mouth l00cc, the nose 60cc and the nasal sinuses 75cc.

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