Anatomy quiz for chapter 4
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Velopharyngeal-Nasal Function and Speech Production
introDuCtion
The velopharyngeal-nasal apparatus is located within the head and neck and comprises a system of valves and air passages. This system interconnects the throat (pharynx) and the atmosphere through the nose. Although most textbooks focus on the velopharyngeal part of this system, this chapter covers the complete velopharyngeal-nasal apparatus as a single functional entity. The chapter begins by discussing the fundamen- tals of velopharyngeal-nasal function, and then turns to consideration of velopharyngeal-nasal function and speech production. The chapter concludes with a review.
FunDamentaLs oF VeLopHarynGeaL-nasaL FunCtion
This section covers the fundamentals of velopharyn- geal-nasal function and lays the groundwork for subse- quent consideration of velopharyngeal-nasal function in speech production. Topics include the anatomy of the velopharyngeal-nasal apparatus, forces and move- ments of the velopharyngeal-nasal apparatus, adjust- ments of the velopharyngeal-nasal apparatus, control variables of velopharyngeal-nasal function, neural sub- strates of velopharyngeal-nasal control, and ventilation and velopharyngeal-nasal function.
anatomy of the Velopharyngeal-nasal apparatus
The valves and air passages of the velopharyngeal- nasal apparatus are linked together such that some of the components are arranged in mechanical series (one after another) and some are arranged in mechanical parallel (side by side). This section begins by discuss- ing the skeletal superstructure that supports the velo- pharyngeal-nasal apparatus. From there, the section proceeds to separate discussions of the anatomy of the pharynx, velum, nasal cavities, and outer nose.
Skeletal Superstructure
Figure 4–1 depicts the skeletal superstructure of the velopharyngeal-nasal apparatus. This superstructure consists of the first six cervical vertebrae and various bones of the skull. The skull bones include bones of the cranium (braincase) and facial complex (forehead, eyes, nose, mouth, and upper throat). These bones are individ- ually intricate structures that are rigidly joined together into a unified framework. This framework contributes to the walls, floor, and roof of the velopharyngeal-nasal apparatus through a system of structural processes, plates, and projections, and provides for the attach- ment of muscles of the velopharyngeal-nasal appa- ratus. Some of the most important bony structures of
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Maxillary bone
Vomer bone
Styloid process
Nasal choana
Palatine bone
Zygomatic bone
Nasal bone
Zygomatic bone
Alveolar process
Mandible
Frontal bone
Temporal bone
Maxillary bone
Cervical vertebrae
Cervical vertebrae
Temporal bone
Styloid process
Mastoid process
Front view Side view
Bottom view (mandible and vertebrae removed)
Mastoid process
FiGure 4–1. Skeletal superstructure of the velopharyngeal-nasal apparatus. The mandible (lower jaw) is shown for reference in front and side views. The bottom view shows the mandible and vertebrae removed.
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4 Velopharyngeal-Nasal Function and Speech Production 121
the apparatus include the temporal bones (sides of the lower braincase), frontal bone (front of the upper braincase), palatine bones (back of the floor of the nasal cavities), maxillary bones (front of the floor of the nasal cavities), sphenoid bone (back wall of the nasal cavities), ethmoid bone (upper side walls of the nasal cavities and upper part of their medial wall), vomer bone (lower part of the medial wall of the nasal cavities), inferior con- chae (lower side walls of the nasal cavities), and nasal
bones (bridge of the outer nose). The bony structures mentioned can be seen in various perspectives in Figure 4–1, in other figures in this chapter, and in depictions of the bony skeleton of the oral apparatus in Chapter 5.
Pharynx
Figure 4–2 depicts some of the salient structural fea- tures of the pharynx (throat). The pharynx is a tube of
Ramus of mandible
Root of tongue (lingual tonsil)
Laryngeal aditus
Esophagus
Pyriform sinus
Epiglottis
Faucial isthmus
Nasal choana
Back view (opened from behind)
Foramen magnum (skull opening for spinal cord)
Velum
FiGure 4–2. Salient features of the pharynx as revealed from a back view in which the posterior pharyngeal wall is opened from behind. The skull, mandible, and selected muscles are shown for reference.
Duane C. spriestersbach (1916–2011)
Duane C. Spriestersbach had a distinguished career as a clinical investigator of communication problems of children with cleft palate and cranio- facial disorders. “Sprie,” as he was affectionately called, served for many years at the University of Iowa as the program director of a large federally funded research grant on cleft palate. His leader- ship fostered much of the research done over two decades on normal velopharyngeal function for speech production and on mechanisms involved in control of the velopharyngeal apparatus in indi-
viduals with velopharyngeal incompetence. Many of the names in this chapter’s reference list cut their research teeth under his guidance. Spriestersbach was an exceptional thinker who had an enormous impact on translating the products of research into practical clinical applications for those with speech disorders caused by cleft palate. In his spare time, he took to the stage, where he performed in the Iowa City Community Theatre, and to the card table, where he played a legendary mean hand of poker.
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Foundations of Speech and Hearing: Anatomy and Physiology122
tendon and muscle that extends from the base of the skull to the cricoid cartilage in the front and to the sixth cervical vertebra in the back. The mix of tendon and muscle varies along the length of the pharynx. The upper end of the structure is made up solely of connective tissue, called the pharyngeal aponeurosis, which effectively suspends the pharyngeal tube from above (the way the rim of a basketball goal suspends the net). Muscular tissue increases in proportion down the length of the pharynx until it predominates. At the lower end, the pharynx is solely muscular and is con- tinuous with the esophagus (gullet), where its front and back walls are in contact. This contact is broken during activities such as swallowing and regurgitation.
The pharyngeal tube is widest at the top and nar- rows down its length. It is oval in cross-section, being larger side to side than front to back. The front wall of the pharynx is partially formed by the back surfaces of the velum (defined below), tongue, and epiglottis. Oth-
erwise, the structure is open at the front and connects, from top to bottom, with the nasal cavities, oral cavity, and laryngeal aditus (upper entrance to the larynx).
The pharynx comprises three cavities that are designated, from top to bottom, as the nasopharynx, oropharynx, and laryngopharynx. The boundaries of these cavities are shown in Figure 4–3. The nasophar- ynx lies behind the nose and above the velum. Because the velum is mobile, the lower boundary of the naso- pharynx is somewhat arbitrary. Thus, a common con- vention is to specify this boundary by a reference line extending between the upper surface of the hard palate and the most forward point on the uppermost vertebra.
The nasopharynx always remains patent, a feature that distinguishes it from the other subdivisions of the pharynx. The pharyngeal orifices of the auditory tubes (also called the eustachian tubes) are located on the lateral walls of the nasopharynx. These tubes enable pressure equilibration between the middle ears and
Nasopharynx
Oropharynx
Laryngopharynx
Tongue
Velum
Nasal cavities
Epiglottis
Esophagus
Cricoid cartilage
Hyoid bone
FiGure 4–3. Boundaries of the nasopharynx, oropharynx, and laryngo- pharynx. The boundary between the nasopharynx and oropharynx can be arbitrary; in this figure it is defined by an imaginary line extending backward at the level of the hard palate. The boundary between the oropharynx and laryngopharynx is the hyoid bone, and the lower boundary of the laryngophar- ynx is the base of the cricoid cartilage.
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4 Velopharyngeal-Nasal Function and Speech Production 123
atmosphere. Across the back surface of the nasophar- ynx, between the pharyngeal orifices of the auditory tubes, lies a large mass of lymphoid tissue called the pharyngeal tonsil. This tissue is also referred to as the nasopharyngeal tonsil and, when abnormally enlarged, is designated as adenoid tissue (or just the adenoids). At the front, the nasopharynx connects to the nasal cavities through the nasal choanae (funnel-like openings). These are two oval-shaped apertures that are about twice as long (top to bottom) as they are wide (side to side) and are oriented in the vertical plane (see Figure 4–2). The nasal choanae are also referred to as the posterior nares (nostrils) or internal nares.
The oropharynx forms the middle part of the pha- ryngeal tube. The upper boundary of the oropharynx is coextensive with the lower boundary of the naso- pharynx. The lower boundary of the oropharynx is the hyoid (tongue) bone. As shown in Figure 4–4, the front of the oropharynx opens into the oral cavity through the faucial isthmus, the narrow passage situated between the velum and the base of the tongue. This isthmus is bounded on the left and right sides by the anterior and posterior faucial pillars, pairs of muscular bands that resemble pairs of legs. The palatine tonsils are located between the anterior and posterior faucial pillars on each side of the isthmus. They are also often called the
faucial tonsils and are “the” tonsils most often referred to colloquially. The back surface of the tongue is the site of yet another tonsil, the so-called lingual tonsil. This tonsil is a broad aggregate of lymph glands distributed across much of the root of the tongue. The oropharynx is the only subdivision of the pharynx that can be seen without special equipment. The back wall of the oro- pharynx is best viewed when the velum is elevated, as in “open your mouth wide and say ‘ah.’”
The laryngopharynx constitutes the lowermost part of the pharynx. The upper boundary of the laryn- gopharynx is the hyoid bone and the lower boundary is the base of the cricoid cartilage, where the pharynx is continuous with the esophagus. At the front, the laryngopharynx is bounded by the back surface of the tongue (and the lingual tonsil), the laryngeal aditus (formed by the epiglottis and aryepiglottic folds), and the pyriform sinuses (pear-shaped cavities located lat- eral to the aryepiglottic folds).
Muscle tissue is an important part of the pharynx and encircles it, much like bands of cord encircle the casing (tread and sidewalls) of a radial automobile tire. In effect, the pharynx is an elongated structure with the architecture of a sphincter. Its overall arrangement is similar to that of the gut. This should come as no
Tongue
Hard palate
Velum (soft palate and uvula)
Palatine tonsil
Back wall of oropharynxPosterior
faucial pillar
Anterior faucial pillar
FiGure 4–4. The oropharynx as seen from the front. The oropharynx is best viewed when instructed to, “open your mouth wide and say ‘ah.’” The narrow opening between the velum and the tongue (top to bottom) and between the anterior faucial pillars (side to side) is called the faucial isthmus.
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Foundations of Speech and Hearing: Anatomy and Physiology124
surprise, because the pharynx is a component of the digestive system.
Velum
The velum, which means curtain, is a pendulous flap consisting of the soft palate and uvula (meaning little grape). In this case, the velum is the curtain that hangs down from the back of the roof of the mouth, as illus- trated in Figures 4–3 and 4–4. A broad sheet of con- nective tissue, the palatal aponeurosis, forms a fibrous skeleton for the velum.
show me your Hand
They were twin girls. Each had speech that was a dead ringer for the speech of the other and that was characterized by multiple misarticulations and hypernasality. What was the cause? Had they developed some sort of twin speech? Did one have a problem that the other was imitating? Oral examinations revealed identical structural anomalies. Each girl had a short velum. Nasoen- doscopic examinations further revealed that, for each girl, the velum elevated only occasionally during speech production, but never came close to the posterior pharyngeal wall. The girls’ parents were with them and being interviewed by a student clinician and her supervisor. The moment the mother spoke, there were suspicions. She had a severe speech disorder characterized by multiple misarticulations and hypernasality, and exhibited pronounced nasal grimacing when speaking. She allowed an oral examination. She had a short velum. It was three of a kind.
Patterns of muscle fiber distribution differ along the length of the velum (Kuehn & Moon, 2005). These include: (a) a front portion that is void of muscle fibers, (b) a middle third that is rich with muscle fibers that course in various directions (including across the mid- line) and include insertions into the lateral margins of the structure, (c) muscle fibers that taper off toward the front and back of the structure, and (d) a uvular (back) portion that is sparsely interspersed with muscle fibers.
Nasal Cavities
The nasal cavities, also termed the nasal fossae (pro- nounced like posse), lie behind the outer nose. They constitute the inner nose and are two large chambers that run side by side. The two nasal cavities are sepa- rated from each other by the nasal septum (not often
perfectly vertical). As shown in Figure 4–5, this parti- tion has: (a) a front part composed of cartilage, (b) an upper back part that is the perpendicular plate of the ethmoid (sieve-like) bone, and (c) a lower back part that is the vomer (ploughshare-like) bone. The floor of the nasal cavities is broad and slightly concave and formed by the hard palate. This floor consists of two sets of bones. The palatine processes of the maxillary bones (left and right upper jaws) form the front three- fourths of the hard palate, and the horizontal processes of the palatine bones form the back one-fourth of the structure. (This can be seen in the bottom image in Fig- ure 4–1). The roof of the nasal cavities, in contrast to the floor, is quite narrow and formed by the cribriform plate of the ethmoid bone. The configuration of the two cavities is similar to the roofline of an A-frame house.
By far the most complex formations within the nasal cavities are located on its lateral walls. These for- mations are convoluted and labyrinthine and contain many nooks and crannies. Three shell-like structures give rise to this complexity. These structures are por- trayed in Figure 4–6 and include the superior, middle, and inferior nasal conchae, formations that extend along the length of the nasal cavities. The nasal con- chae, also called the nasal turbinates, have correspond- ing meatuses (passages) named for the conchae with which they are associated. The enfolding structure of
Cartilage
Vomer bone
Ethmoid bone
Frontal bone
Nasal bone
Maxillary bone
Teeth Palatine bone
FiGure 4–5. Components of the nasal septum (parti- tion between the two nasal cavities). The nasal septum con- sists of cartilage at the front and bone (ethmoid and vomer) in the back. Selected other bones and teeth are shown for reference.
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4 Velopharyngeal-Nasal Function and Speech Production 125
the nasal cavities provides a large surface area to the inner nose and has a rich blood supply. A final struc- ture of interest in each nasal cavity is the nasal vesti- bule, a modest dilation just inside the aperture of the anterior naris.
Outer Nose
Unlike the other components of the velopharyngeal- nasal apparatus, the outer nose is familiar to everyone, especially the surface features of the structure. The outer nose is hard to ignore because it is in the cen- ter of the face and projects outward and downward conspicuously. The more prominent surface features of the outer nose include the root, bridge, dorsum, apex, alae, base, septum, and anterior nares, as shown in Figure 4–7.
The root (point of attachment) of the outer nose is to the bottom of the forehead. Following downward along the center line are the bridge (upper bony part), dorsum (prominent upper surface), and apex (tip). The alae (wings) form much of the sides of the nose and contribute significantly to its general shape. The base of the nose constitutes the bottom of the struc- ture, partitioned down the middle (more or less) by the lowermost part of the nasal septum, and includ- ing the anterior nares (nostrils). The anterior nares are also referred to as the external nares and are somewhat
Superior nasal concha
Inferior nasal concha
Nasal vestibule
Middle nasal concha
FiGure 4–6. Superior, middle, and inferior nasal con- chae (also called nasal turbinates). These conchae contain many nooks and crannies and create a large surface area to the inner nose.
Root
Ala
Anterior naris
Base
Bridge
Dorsum
Apex
Septum
FiGure 4–7. Surface features of the outer nose.
Disposing of things
Mucus (a slimy substance) is formed in the nose to the tune of about half a pint a day (more when you have a cold). Particles filtered by the nose are collected in a blanket of mucus and moved through the nose by the action of cilia (tiny hair cells that collectively form a fringe). Things that get trapped are moved along toward the back of the throat and then swallowed into the stomach. Some material dries before reaching the back of the throat and fractionates into pieces contain- ing filtered particles. This happens at different spots within the nose and in residues of various consistencies. Prim and proper folks refer to these residues as nasal exudates or pieces of dried nasal mucus. Most of us refer to them as “boogers.” They are best gently blown into a tissue to rid them from the nose, but we all know other manual methods that are commonly practiced.
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Foundations of Speech and Hearing: Anatomy and Physiology
pear-shaped apertures that are typically about twice as long (front-to-back) as they are wide (side-to-side). Margins of the anterior nares include stiff hairs, called vibrissae. These hairs arrest the passage of particles rid- ing on air currents.
Forces and movements of the Velopharyngeal-nasal apparatus
Much of the functional potential of the velopharyn- geal-nasal apparatus lies in its capacity for movement. This movement is caused by forces applied to and by different components of the apparatus.
Forces of the Velopharyngeal-Nasal Apparatus
The forces operating on the velopharyngeal-nasal apparatus are of two types: passive and active. Passive force is inherent and always present (although subject to change), whereas active force is applied depending on the will and ability of the individual.
Passive Force
The passive force of velopharyngeal-nasal function arises from several sources. These include the natural recoil of muscles, cartilages, and connective tissues, the surface tension between structures in apposition, the pull of gravity, and aeromechanical forces within the upper airway (throat, mouth, and nose).
The distribution, sign, and magnitude of passive force depend on the prevailing mechanical conditions, including the positions, deformations, and levels of activity of different components of the velopharyngeal- nasal apparatus. For example, the pull of gravity dif- ferentially influences velopharyngeal-nasal function when body position is changed. Such influences are considered in detail in another section.
Active Force
The active force of velopharyngeal-nasal function arises from muscles distributed within different com- ponents of the velopharyngeal-nasal apparatus. This active force results from the contraction of muscle fibers. The contribution of specific muscles to such force generation is not completely understood. Never- theless, based on individual muscle architecture, con- sequences of muscle activation, and observations of the electrical activity of muscles during various activities, the probable roles of specific muscles can be specified with reasonable certainty.
The function described here for individual mus- cles assumes that the muscle under consideration is
activated and involved in a shortening (concentric) contraction. The influence of individual muscle actions depends on whether or not related muscles are active, on the mechanical status of different components of the velopharyngeal-nasal apparatus, and on the nature of the activity being performed. The muscles of the phar- ynx, velum, and outer nose are considered below.
Muscles of the Pharynx. Figure 4–8 portrays the mus- cles of the pharynx. They are the superior constrictor, middle constrictor, inferior constrictor, salpingo pharyngeus, stylopharyngeus, and palatopharyngeus muscles. These muscles influence the size and shape of the lumen (cavity) of the pharyngeal tube. Of course, other structures along the front side of the pharynx can also influence the lumen of the pharynx through their adjustments (velum, tongue, and epiglottis).
The superior constrictor muscle is located in the upper part of the pharynx. It is a complex muscle with multiple origins that arise from the front of the pha- ryngeal tube. Front points of attachment include the medial pterygoid plate (of the sphenoid bone), the pterygomandibular ligament (a tendinous inscription between the superior constrictor muscle and the buc cinator muscle, described in Chapter 5), the mylohy- oid line (site of attachment of the mylohyoid muscle, described in Chapter 5, on the inner surface of the body of the mandible), and the side of the back part of the tongue. Fibers from the multiple origins of the supe rior constrictor muscle course backward, toward the midline, and upward to insert into the fibrous median raphe (seam) of the posterior pharyngeal wall. There, they join with fibers of the paired muscle from the opposite side. The uppermost fibers of the superior constrictor muscle are horizontal and located at the level of the velum. When the superior constrictor mus- cle contracts, it reduces the regional cross section of the pharyngeal lumen by forward movement of the poste- rior pharyngeal wall and forward and inward move- ment of the lateral pharyngeal wall on the same side. The paired superior constrictor muscles encircle the posterior and lateral walls of the upper pharynx (recall the radial tire analogy from above), so that their simul- taneous contraction constricts the lumen of that part of the pharyngeal tube in the manner of a sphincter.
The middle constrictor muscle is a fan-shaped structure located midway along the length of the pharyngeal tube. Fibers of the muscle arise from the greater and lesser horns of the hyoid bone and the sty- lohyoid ligament (which runs between the downward and forward projecting styloid process of the temporal bone and the lesser horn of the hyoid bone) and radiate backward and toward the midline where they insert into the median raphe of the pharynx. The uppermost
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127
Side view
Palatopharyngeus
Superior constrictor
Middle constrictor
Inferior constrictor
Superior constrictor
Middle constrictor
Inferior constrictor
Back view
Salpingopharyngeus
Stylopharyngeus
FiGure 4–8. Muscles of the pharynx. The superior constrictor, middle constrictor, inferior constrictor, salpingopha- ryngeus, and palatopharyngeus muscles constrict the pharynx, whereas the stylopharyngeus muscle dilates the pharynx. Some of these muscles can also move the pharynx in other ways (see Figure 4–9).
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Foundations of Speech and Hearing: Anatomy and Physiology128
fibers of the middle constrictor muscle course obliquely upward and overlap the lower fibers of the superior constrictor muscle, whereas the lowermost fibers of the muscle run obliquely downward beneath the fibers of the inferior constrictor muscle. The middle fibers of the middle constrictor muscle run horizontally. The overlapping arrangement of the muscle fibers between the middle constrictor and superior constrictor mus- cles and between the inferior constrictor and middle constrictor muscles is akin to the way roof shingles partially overlap. When the middle constrictor muscle contracts, it decreases the cross section of the pharynx regionally, by virtue of forward movement of the pos- terior pharyngeal wall and forward and inward move- ment of the lateral pharyngeal wall. When the middle constrictor muscle acts in conjunction with its paired mate on the opposite side, the pharyngeal lumen is regionally constricted like a sphincter.
The inferior constrictor muscle is the most pow- erful of the three constrictor muscles of the pharynx. The fibers of this muscle arise from the sides of the thyroid and cricoid cartilages. The inferior constrictor muscle is sometimes thought of as consisting of two muscles, referred to as the thyropharyngeus and crico pharyngeus muscles. From the origins noted, fibers of the inferior constrictor muscle diverge in a fanlike con- figuration and course backward and toward the mid- line. There, they interdigitate with fibers from the inferior constrictor muscle of the opposite side at the median raphe of the pharyngeal tube. The middle and upper fibers of the inferior constrictor muscle ascend obliquely, whereas the lowermost fibers run horizon- tally and downward and are continuous with those of the esophagus. When the inferior constrictor muscle contracts, it draws the lower part of the posterior wall of the pharynx forward and pulls the lateral walls of the lower pharynx forward and inward. This action, in conjunction with that of the inferior constrictor muscle on the opposite side, constricts the lumen of the lower pharynx.
The salpingopharyngeus muscle is a narrow muscle that arises from near the lower border of the pharyngeal orifice of the auditory tube. The fibers of the muscle course downward vertically and insert into the lateral wall of the lower pharynx where they blend with fibers of the palatopharyngeus muscle (discussed below). When the salpingopharyngeus muscle con- tracts, it pulls the lateral wall of the pharynx upward and inward. When acting simultaneously with its paired muscle from the opposite side, its effect is to decrease the width of the pharynx.
The stylopharyngeus muscle is a slender muscle that runs a relatively long course. It originates from the styloid process of the temporal bone and runs down-
ward, forward, and toward the midline. Most fibers of the muscle insert into the lateral wall of the pharynx at and near the juncture of the superior constrictor and middle constrictor muscles. Some fibers extend lower in the pharyngeal wall and insert into the thyroid car- tilage. When the stylopharyngeus muscle contracts, it pulls upward on the pharyngeal tube and draws the lateral wall of the pharynx toward the side. Together with similar action of its paired mate from the opposite side, it widens the lumen of the pharynx in the region where the muscle fibers insert into the lateral walls of the pharyngeal tube. There is also an upward pull placed on the pharynx (and larynx) when the stylopha ryngeus muscles contract.
The palatopharyngeus muscle runs the length of the pharynx. It is a pharyngeal muscle as well as a mus- cle of the soft palate (and in that context is called the pharyngopalatine muscle). The muscle is considered here from the pharyngeal perspective. The palatopha ryngeus muscle arises mainly from the soft palate. The uppermost fibers are directed horizontally and inter- mingle with fibers of the superior constrictor muscle. A major fiber course is downward and toward the side through the posterior faucial pillar. Below the pillar, the fibers continue into the lower half of the pharynx and spread to the lateral wall of the structure and the thyroid cartilage. Some have suggested that the por- tion of the muscle that attaches to the thyroid cartilage be given recognition of its own as the palatothyroi deus muscle (Cassell & Elkadi, 1995), whereas others
Having it Both Ways
A muscle is usually thought of as having an origin and an insertion. The origin is its anchored end and the insertion is its movable end. This is all well and good in textbooks, but in real life things are a bit more complicated. What may be the anchored end of a muscle for one activity may be the movable end of that muscle for another activity. A lot of it has to do with what neighboring muscles are doing. Thus, a muscle’s function may change from time to time because various forces cause the mobility of its two ends to change in relation to one another. The convention adopted in this book is to reflect such change by alternately labeling a muscle in accordance with its perceived primary func- tion in a given context. Some purists may not embrace this convention, but it carries instruc- tive power and simply points out that in the busy world of the muscle, turn about is fair play.
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4 Velopharyngeal-Nasal Function and Speech Production 129
disagree (Moon & Kuehn, 2004). When the velum is relatively stable, contraction of the palatopharyngeus muscle results in two movements. The uppermost fibers of the muscle draw the lateral pharyngeal wall inward to complement the action of the superior con strictor muscle, whereas the lowermost fibers pull upward on the lateral pharyngeal wall and elevate the pharynx. (Attachments to the thyroid cartilage also effect an upward and forward pull on the larynx).
Figure 4–9 illustrates the general force vectors for the six muscles of the pharynx discussed in this sec- tion. This illustration summarizes the potential active forces operating on the pharynx and shows the combi- nations of forces that could be in play at any moment to decrease or increase the lumen of the pharynx and/ or change its positioning.
Muscles of the Velum. The muscles of the velum are shown in Figure 4–10. They are the palatal levator,
palatal tensor, uvulus, glossopalatine, and pharyn gopalatine muscles. These muscles influence the posi- tioning, configuration, and mechanical status of the velum.
The palatal levator muscle (also called the leva tor veli palatini muscle) forms much of the bulk of the velum. The palatal levator muscle is a flattened cylin- drical structure that arises from the petrous (hard) por- tion of the temporal bone and from the cartilaginous portion of the auditory tube. From there, it courses downward, forward, and toward the midline, pass- ing on the outside of the posterior naris. Fibers of the palatal levator muscle insert into the side of the velum and spread out where they join those of the palatal levator muscle from the opposite side. The spread of muscle fibers in each of the palatal levator muscles is to the midline and beyond to the other side of the velum (Kuehn & Moon, 2005). Fibers extend from behind the hard palate to the front of the uvula, en-
Side view Front view
Superior constrictor
Middle constrictor
Inferior constrictor
22
33
11
55
66
44 Salpingopharyngeus
Stylopharyngeus
Palatopharyngeus
55
22
11
33
66 55
44
66
44
FiGure 4–9. Summary of force vectors of the muscles of the pharynx. The superior constrictor (1), middle constrictor (2), and inferior constric- tor (3) muscles constrict the pharynx. The salpingopharyngeus (4) and palatopharyngeus (6) muscles pull upward and inward on the pharynx. The stylopharyngeus muscle (5) pulls upward and outward on the pharynx.
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Foundations of Speech and Hearing: Anatomy and Physiology130
compassing approximately the middle 40% of the velum (Boorman & Sommerlad, 1985) or more (Kuehn & Kahane, 1990). The paired palatal levator muscles form a muscular sling from their cranial attachments through the velum. Each palatal levator muscle inserts into the velum at an angle of about 45°. When the palatal levator muscle contracts, it draws the velum upward and backward. Simultaneous contraction of the paired palatal levator muscles lifts the velum toward the posterior pharyngeal wall along an angular trajectory.
The palatal tensor muscle (also termed the tensor veli palatini muscle) lies on the outer side of the pal atal levator muscle. It arises from the pterygoid and scapular fossae and angular spine of the sphenoid bone as well as the cartilaginous portion of the auditory tube. From there, fibers course vertically downward to terminate in a tendon and insert into the hook-shaped hamulus of the medial pterygoid plate of the sphenoid bone. The tendon of the palatal tensor muscle (along
with a sparse number of palatal tensor muscle fibers) courses inward and inserts into the hard palate and the velum (Barsoumian, Kuehn, Moon, & Canady, 1998). The palatal tensor muscle has an important role in opening the auditory tube. Earlier conceptions of the function of the palatal tensor muscle also suggested that its contraction would tense the velum, because it was thought that the muscle itself wrapped around the hamulus to contribute to the horizontal portion of the structure. However, the fact that the palatal tensor muscle is now known to insert on the hamulus, with only a few fibers continuing on to insert into the velum, indicates that it does not have the mechanical means to tense the velum to any significant degree. In contrast, the tendon does seem to play an important mechanical role. The prominent size of this tendon suggests that it may relieve stress at the junction between the hard and soft palates, stress induced by frequent up-and-down movements of the velum. The stress-relief function is believed to be akin to a reinforced collar at the junction
Uvulus Pharyngopalatine
Palatal levator
Palatal tensor
Glossopalatine
Back view
Side view
FiGure 4–10. Muscles of the velum. They are the palatal levator, palatal tensor, uvulus, glossopalatine, and pharyn- gopalatine muscles. Most of these muscles act primarily to move the velum upward and backward and downward and forward. Their individual actions are shown schematically in Figure 4–11.
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4 Velopharyngeal-Nasal Function and Speech Production 131
between an electrical plug and the wire extending from it (Kuehn, 1990).
The uvulus muscle is the only intrinsic muscle of the velum. (Both ends of it fibers are within the velum). Fibers of the muscle originate to the side of the posterior nasal spine formed by the palatine bones and behind the hard palate near the sling formed by the palatal levator muscles and about a fourth of the way along the length of the soft palate from the front. The muscle courses downward and backward, extending through much of the length of the soft palate. Very few fibers of the uvulus muscle actually enter the uvula proper, from which the muscle historically derived its name (Azzam & Kuehn, 1977; Huang, Lee, & Rajendran, 1997). This has prompted some to argue (and seemingly rightfully so) that calling this muscle the uvulus muscle is both a misnomer and anatomically misleading (Moon & Kuehn, 2004). When the uvulus muscle contracts, it has several effects that can be realized alone or in combina- tion. These include (a) shortening the velum, (b) lifting the velum, and (c) increasing the thickness (bulk) of the velum in the third quadrant of its length.
The glossopalatine muscle is both a muscle of the tongue and a muscle of the velum, and is discussed here as a muscle of the velum. Fibers of the glossopala tine muscle arise from the side of the tongue where they are closely blended with longitudinal fibers of the dor- sum of the tongue. They course upward and inward, forming the substance of the anterior faucial pillar, and insert into the lower surface of the palatal aponeurosis. The location of attachment to the soft palate is reported to vary across individuals, with some having inser- tions forward near the hard palate and others having insertions rearward near the uvula (Kuehn & Azzam, 1978). When the dorsum of the tongue is relatively fixed, contraction of the glossopalatine muscle places a downward and forward pull on the velum. Although the glossopalatine muscle has force potential on the velum, that potential is limited in comparison to the force potential of the pharyngopalatine muscle (Moon & Kuehn, 2004).
The pharyngopalatine muscle (discussed above as the palatopharyngeus muscle in the context of the pharynx) is considered here in the context of the velum. Its fibers arise from the lower half of the lateral wall of the pharynx and thyroid cartilage and course upward and toward the midline where they pass through the posterior faucial pillar and insert into the soft palate (also the superior constrictor muscle). Fibers do not approach or cross the midline of the soft palate, but insert more laterally within the structure (Kuehn & Kahane, 1990). One notion of mechanical prominence is that there is a downward directed sling formed by
the pharyngopalatine muscles that is antagonistic to the upward directed sling provided by the palatal leva tor muscles (Fritzell, 1969), although this idea has been questioned on anatomical grounds (Moon & Kuehn, 2004).
When the pharyngeal attachment of the pharyn gopalatine muscle is relatively fixed, contraction of its fibers (especially those which are vertically oriented) pulls downward and backward on the velum. The action suggested here is founded on assumed muscle vector pulls inferred from anatomical observations. This approach may or may not be wholly correct.
Figure 4–11 graphically illustrates the general force vectors for the four muscles that are known to operate on the velum. The palatal tensor muscle is not included in this figure because it does not appear to have a significant role in velar function.
Muscles of the Outer Nose. All of the muscles of the outer nose can be used for facial expression to convey meaning. For the purposes of this chapter, however, interest in these muscles is in their potential to influ- ence velopharyngeal-nasal function. Five outer nose muscles, shown in Figure 4–12, have this potential and it is these muscles that are discussed here.
The levator labii superioris alaeque nasi muscle (the longest name of any muscle in animals) is a thin structure located at the side of the outer nose between the orbit of the eye and the upper lip. Its origin is from the frontal process and infraorbital margin of the maxilla. From there, the muscle courses downward and toward the side, subdividing into two muscular slips. One slip inserts into the upper lip (blending with the orbicularis oris muscle, described in Chap- ter 5) and the other slip (of more interest here) inserts into the cartilage of the nasal ala (see Figure 4–7). Contraction of this latter muscular slip draws the ala upward on the same side of the outer nose (like lifting a side flap on a tent) and enlarges the cor- responding anterior naris.
The anterior nasal dilator muscle is a small muscle positioned on the lower lateral surface of the outer nose. It arises from the lower edge of the lateral nasal cartilage and runs downward and outward. Fol- lowing a short course, it inserts into the deep surface of the skin near the outer margin of the naris on the same side. Contraction of the anterior nasal dilator muscle enlarges the anterior naris on that side of the outer nose.
The posterior nasal dilator muscle is a small muscle located on the lower lateral surface of the outer nose. It lies behind the anterior nasal dilator muscle. Fibers of the posterior nasal dilator muscle originate
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Foundations of Speech and Hearing: Anatomy and Physiology132
from the nasal notch of the maxilla and adjacent sesa- moid cartilages of the outer nose. From this origin, they follow a short course and insert into the skin near the lower part of the alar cartilage along the outer margin of the naris on the same side. Contraction of the pos
terior nasal dilator muscle enlarges the corresponding anterior naris.
The nasalis muscle is located on the side of the outer nose. It originates from the maxilla, above and lateral to the incisive fossa. Fibers run upward and
22
11
44 44
22
11
33
11
33
Palatal levator
Uvulus
Glossopalatine
Pharyngopalatine
22
33
11
44
Side view
Front view
Left oblique view
33 44
FiGure 4–11. Summary of force vectors of the muscles of the velum. The palatal levator muscle (1) pulls the velum upward and backward. The uvulus muscle (2) shortens, lifts, and increases the thickness of the velum. The glossopalatine muscle (3) pulls the velum downward and forward and the pharyngopalatine muscle (4) pulls the velum downward and backward. The palatal tensor muscle is not included in this figure because it is not thought to have a significant effect on the velum.
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4 Velopharyngeal-Nasal Function and Speech Production 133
toward the midline and insert into an aponeurosis that is continuous with its paired muscle from the opposite side. When the nasalis muscle contracts, it draws down the cartilaginous part of the outer nose on the same side and decreases the aperture of the corresponding anterior naris. Under extreme action, contraction of this muscle and its counterpart from the opposite side may bring the two alae of the outer nose together or com- press them against one another.
The depressor alae nasi muscle is a short muscle that originates from the incisive fossa of the maxilla and radiates upward to insert into the back part of the ala and the cartilaginous septum of the outer nose. When the depressor alae nasi muscle contracts, it draws the ala of the outer nose downward on the side of action and decreases the aperture of the cor- responding naris.
Movements of the Velopharyngeal-Nasal Apparatus
Movements of the pharynx, velum, and outer nose are considered here apart from the forces that cause them. The relation of forces to movements is considered in the next section on adjustments.
Movements of the Pharynx
The pharynx is a highly mobile tube. As illustrated in Figure 4–13, this mobility is vested in structures of the pharynx itself and in structures that comprise its lower and front boundaries. These movement capabilities are: (a) lengthening and shortening through downward and upward movements of the larynx, (b) inward and outward movements of the lateral pharyngeal walls, (c) forward and backward movements of the posterior pharyngeal wall, and (d) forward and backward move- ments of velum, tongue, and epiglottis. Because the pharynx is a hollow tube, movements of the pharynx are manifested in changes in the shape of its internal cavity. This internal cavity can be constricted or dilated at multiple sites as the result of different combinations of movements of the structure. For example, one part of the pharynx may be constricted, another part dilated, and yet another part alternately constricted and dilated during an activity.
Movements of the Velum
The velum is a fleshy flap that is largely muscular. Most of the time, it hangs pendulously in the oropharyngeal space, but for many activities it moves substantially.
Anterior nasal dilator
Posterior nasal dilator
Levator labii superioris
alaeque nasi
Nasalis
Depressor alae nasi
FiGure 4–12. Muscles of the outer nose. Three muscles dilate the nares (levator labii superioris alaeque nasi, anterior nasal dilator, and posterior nasal dilator muscles) and two constrict the nares (nasalis and depressor alae nasi muscles) when contracted.
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Foundations of Speech and Hearing: Anatomy and Physiology134
Tongue
Skull
Side wall
Epiglottis
Esophagus
Velum
Side wall
Back wall
Larynx
Skull
Mouth of esophagus
(behind)
Cricoid lamina
Front view Side view
FiGure 4–13. Movements of the pharynx. These movements can be downward and upward, inward and outward, and forward and backward and can lengthen, shorten, widen, and constrict the pharyngeal tube. Some of these movements are carried out by parts of the pharynx and others are carried out by nearby structures (velum, tongue, epiglottis, and larynx).
sonar in a teacup
Early study of lateral pharyngeal wall movement was problematic because x-ray techniques of the day did not provide good frontal views of the pharynx. Two speech scientists and a medical physicist from the University of Wisconsin provided the first clean data on lateral pharyngeal wall movement through the use of pulsed ultrasound. The technique sounded the depth of a point on the pharyngeal wall (like tracking a submarine). To learn the technique, they attended a short course on obstetrics where the uses of ultrasound were being taught as a pioneering means for scanning the abdomen of pregnant women. The first monitoring of lateral pharyn- geal wall movement during speech production was done at that short course, on an individual immersed (except for the face) in a water-filled gunner ’s turret of a bomber (envision an enormous teacup). Gels were just then starting to be used to transmit ultrasound into the body for medical purposes.
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4 Velopharyngeal-Nasal Function and Speech Production 135
Movements of the velum are mainly along an upward- backward or downward-forward path, in which those in one direction closely trace those in the other. The angular trajectory is reported to be slightly curvilin- ear (Kent, Carney, & Severeid, 1974) or linear (Kuehn, 1976). Maximum upward movement of the velum places the upper surface of the structure within the nasopharynx (above the boundary specified by con- vention to separate the oropharynx and nasopharynx).
Lubker Bumps
Scientists often name phenomena for those who were first to describe them or to figure out what they meant. In this regard, the inauguration of the term “Lubker Bumps” seems long overdue. Most who have studied velopharyngeal-nasal function using aeromechanical techniques have encountered very small variations in nasal airflow (usually oscillating around zero airflow) when the velopharynx is closed airtight. These variations, as described by James F. Lubker, result from movements of the velum up and down within a closed velopharynx, acting like a piston in a cylinder to push very small quantities of air in and out of the nasopharynx. The nasal airflow tracings that characterize such piston movements show tiny bumps up and down around zero airflow that reflect true airflows, but ones not generated by the passage of air through the velopharynx. Lubker ’s reputation deserves to be bumped up a notch for his astute observation.
The velum is a flap and in some ways it resembles a trapdoor, but it does not move like a trapdoor, as if it were swinging from a hinge. Rather, as depicted in Figure 4–14, the shape of the velum actually changes when it moves. The farther up and back it moves, the more “hooked” its appearance (as viewed from the side) and the farther down and forward it moves, the more “pendulous” its appearance (as viewed from the side). This is because the major lifting force that pulls the velum upward is applied toward the middle of the velum. The hooked appearance of the velum results in identifiable landmarks during movement. The top of the hook (on the upper surface of the velum) is referred to as the velar eminence and the undersurface of the hook (on the lower surface of the velum) is designated as the dimple of the velum.
Movements of the Outer Nose
Movements of the outer nose result mainly from out- ward or inward movements of the nasal alae that may change the cross sections of the apertures of the ante- rior nares (nostrils). Under most circumstances, these movements are small. Exceptions occur during certain breathing events, when signaling emotions (disdain, contempt, and anger), and when using the nares to slow the flow of air from the outer nose by increasing resistance at its exit ports.
adjustments of the Velopharyngeal-nasal apparatus
The velopharyngeal-nasal apparatus is capable of many adjustments. The present discussion is limited to those adjustments that influence the degree of cou- pling between the oral and nasal cavities (through the velopharyngeal port) and between the nasal cavities and atmosphere (through the apertures of the anterior nares). Adjustments of lower parts of the pharynx are considered in Chapters 5 and 8.
Nasopharynx
Oropharynx
Velar eminence
Velar dimple
FiGure 4–14. Elevated configuration of the velum as viewed from the side. Note its “hooked” appearance. The upper surface of the hook is called the velar eminence and the undersurface of the hook is called the velar dimple.
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Foundations of Speech and Hearing: Anatomy and Physiology136
Coupling Between the Oral and Nasal Cavities
The degree of coupling between the oral and nasal cav- ities can be adjusted by changing the size of the velo- pharyngeal port (the usual opening between the oral and nasal cavities). The range of possibilities extends from a fully open port to a fully closed port.
The velopharyngeal port is open most of the time to accommodate nasal breathing. Closure of the port can be brought about through action of the velum and/ or pharynx. Combined action of the two structures is often described as a flap-sphincter action, the flap
being movement of the velum and the sphincter being movement of the pharynx.
There is no universal pattern for achieving velo- pharyngeal closure. On the contrary, several movement strategies for achieving closure of the velopharyngeal port have been identified that involve different actions or combinations of actions of the velum, lateral pha- ryngeal walls, and posterior pharyngeal wall (Croft, Shprintzen, & Rakoff, 1981; Finkelstein et al., 1995; Poppelreuter, Engelke, & Bruns, 2000; Shprintzen, 1992; Skolnik, McCall, & Barnes, 1973). These movement strategies are illustrated in Figure 4–15 and include: (a) elevation of the velum alone, (b) inward movement of the lateral pharyngeal walls alone, (c) elevation of the velum combined with inward movement of the lat- eral pharyngeal walls, and (d) elevation of the velum combined with inward movement of the lateral pha- ryngeal walls and forward movement of the posterior pharyngeal wall.
The prevailing wisdom is that these different movement strategies for achieving velopharyngeal clo- sure are rooted in differences in anatomy (Finkelstein et al., 1995). It should also be noted that different move- ment strategies for achieving closure of the velopha- ryngeal port are not fixed within individuals, but can change over time as velopharyngeal anatomy changes.
The positioning of the velum in the adjustment of oral-nasal coupling is most often attributed to action of the paired palatal levator muscles (Dickson, 1972). Thought typically has been that lifting of the velum fol- lows from the contractile force provided by these mus- cles and accounts for its midportion usually attaining the highest elevation during closure of the velopharyn- geal port (Bell-Berti, 1976; Fritzell, 1963; Lubker, 1968; Seaver & Kuehn, 1980). Although action of the palatal levator muscle seems to be clearly associated with the flap component of the flap-sphincter closure adjust- ment, correlations between palatal levator activity and the elevation of the velum are weaker (albeit posi- tive) than would be expected were the palatal leva tor muscle alone responsible for positioning the velum (Fritzell, 1979; Lubker, 1968). This suggests that other muscles must also be active in positioning the velum. Research, in fact, supports this inference. For example, different combinations of muscle activity among the palatal levator, glossopalatine, and pharyngopala tine muscles have been found to be associated with the same positioning of the velum (Kuehn, Folkins, & Cutting, 1982). This and other evidence (Moon, Smith, Folkins, Lemke, & Gartlan, 1994b) suggest that there is a trading relationship among these three muscles that contribute to movements of the velum. Clearly, classi- cal notions of the velum being controlled by the palatal levator muscle alone is not adequate.
Back wall of pharynx
Side wall of pharynx
(right)
Side wall of pharynx
(left)
Top surface of velum
A
B
C
D
FiGure 4–15. Patterns of velopharyngeal closure as seen from above. These patterns are velar elevation (A), inward movement of the lateral pharyngeal walls (B), com- bined velar elevation and inward movement of the lateral pharyngeal walls (C), and velar elevation combined with inward movement of the lateral pharyngeal walls and for- ward movement of the posterior pharyngeal wall (D).
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4 Velopharyngeal-Nasal Function and Speech Production 137
Coupling Between the Nasal Cavities and Atmosphere
The degree of coupling between the nasal cavities and atmosphere can be adjusted by changing the size of the anterior nares. The range of possibilities extends from fully open nares to fully closed nares. It is also possible to have different degrees of coupling for the two nares (one being open more than the other).
Where’s the rest?
Many studies have examined the correlation between velopharyngeal incompetence and articulation skill in children with repaired cleft palates. The highest correlation found in these studies is 0.5. Square that number and you find that velopharyngeal incompetence predicts only 25% of the variance in articulation skill. Where’s the rest? Some have suggested it’s to be found in “learning.” We believe 75% is far too much to be attributed to such a notion. Rather, we suspect that the rest is confounded by the fact that the children studied were never categorized with regard to the magnitude of their nasal airway resistance. Not knowing or controlling for this factor would have an important influence on the strength of the correlation obtained between velopharyngeal incompetence and articulation skill. Where’s the rest of the variance of interest? We think it’s probably in the nose and has been overlooked.
The anterior nares, like the velopharynx, are rel- atively open most of the time to accommodate nasal breathing. Dilation or constriction of the nares can be brought about through actions of muscles of the outer nose. Such actions can be either opposed or supple- mented by aeromechanical forces associated with breathing. For example, muscles that dilate the anterior nares may activate to resist the tendency of the nares to collapse in response to low air pressures (created by high airflows) in their lumina. The need for such activation can be appreciated by sniffing briskly while watching the outer nose in a mirror. Both the nares and alae of the outer nose tend to be sucked inward by the lowering of nasal pressures. More forceful inspirations require increasingly forceful contractions of nasal dilators to maintain patent nares (Bridger, 1970).
Control Variables of Velopharyngeal-nasal Function
Several control variables are important in velopharyn- geal-nasal function. Their relative significance depends on the particular activity being performed and its goal, whether it is breathing, speaking, singing, blowing, sucking, swallowing, gagging, whistling, playing a wind instrument, or blowing glass. For example, speak- ing involves control variables based on acoustic goals, whereas tidal breathing does not. For another example, the force with which the velopharynx is closed may be an important variable for an activity that calls for very high oral air pressure (glass blowing), but be a less important variable for an activity with low oral air pressure demands (whispering). For persons with a normally functioning velopharyngeal-nasal appa- ratus, the most significant features of control pertain to the velopharyngeal portion of the apparatus. There are times, however, when control of the outer nose can become important.
For purposes of this chapter, attention is devoted to three control variables that influence aeromechanical and acoustic aspects of velopharyngeal-nasal function. These include: (a) the magnitude of the airway resis- tance offered by the velopharyngeal-nasal apparatus, (b) the magnitude of the muscular pressure exerted by the velopharyngeal sphincter to accomplish and main- tain velopharyngeal closure, and (c) the magnitude of the acoustic impedance offered by the velopharyngeal- nasal apparatus.
Velopharyngeal-Nasal Airway Resistance
Resistance is defined, in a mechanical sense, as opposi- tion to movement and results in a loss of energy through friction. Velopharyngeal-nasal airway resistance has to do with opposition to the mass flow of air (the breath) through structures of the velopharyngeal-nasal airway. This is analogous to the resistance to airflow through the laryngeal airway, discussed in Chapter 3.
Adjustments of the velopharyngeal port, nasal cavities, and/or outer nose can create a change in airway resistance between the oral cavity and atmo- sphere through the nasal route, as portrayed in Fig- ure 4–16. Changing the cross section and/or length of the velopharyngeal port, changing the engorgement of the nasal cavities, or changing the cross section of the anterior nares can all have consequences for velo- pharyngeal-nasal airway resistance. Airflow also alters the resistance because resistance is airflow depen- dent. Specifically, resistance increases and decreases with increases and decreases in the rate at which the
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Foundations of Speech and Hearing: Anatomy and Physiology138
air moves, even when the physical dimensions of the velopharyngeal-nasal airway remain unchanged.
The range of potential airway resistance values is large and can go from very low (following the admin- istration of a decongestant) to infinity (completely
obstructed). Infinite airway resistance is usually effected through airtight closure of the velopharyngeal port. Infinite velopharyngeal-nasal airway resistance can also be achieved in the case of an open velopharynx under circumstances where there is complete nasal blockage.
Outer nose
Nasal cavities
Mass airflow
Velopharyngeal port
FiGure 4–16. Airflow through the velopharyngeal-nasal apparatus. The resistance of the velopharyngeal-nasal apparatus to air flowing through it can be altered by adjustments of the velopharyngeal port, the nasal cavities, and the outer nose. Changes in the rate at which air flows through the apparatus can also alter the resistance.
the Flap Flap
Pharyngeal flaps are secondary surgical procedures usually performed on persons with repaired cleft palates who persist with velopharyngeal incom- petence or insufficiency following primary surgery. Flaps are constructed using tissue from the posterior pharyngeal wall (peeled away like the skin on a banana) and attaching it to the velum to form a bridge. Flaps have also been used in children with cerebral palsy who have paresis (weakness) of the velar muscles. Such flaps have been found to improve speech in such children, but they also have been found to have a major negative side effect. They may raise the resistance to breathing through the nose and cause some children to switch from nose breathing to mouth breathing. Mouth breathing opens the door (pun intended) to drooling. The negative social consequences of drooling are often judged to outweigh the positive social consequences of improved speech. Thus, flaps sometimes have had to be removed.
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4 Velopharyngeal-Nasal Function and Speech Production 139
Velopharyngeal Sphincter Compression
Once airtight velopharyngeal closure is attained, the force of that closure can be adjusted to meet the needs of the situation. This force, depicted in Figure 4–17,
is represented by the compressive muscular pressure exerted to maintain the velopharyngeal sphincter in a closed configuration. The muscular pressure exerted at any moment must exceed the magnitude of the air pressure difference across the velopharyngeal sphincter
Side wall of pharynx
(right)
Back wall of pharynx
Side wall of pharynx
(left)
Top surface of velum
FiGure 4–17. Compressive muscular pressure during velopharyngeal closure. The greater the pressure difference across the velopharynx, the higher the compressive pressure needed to maintain velopharyngeal closure. The inset shows the velopharynx as if viewed from above.
some things are not Quite What they seem
There seems to be a relatively large number of musicians who complain of “air leaks out the nose” while playing wind instruments. Such complaints are red flags for what is often called stress-induced velopharyngeal incompetence. Sometimes physical measurements confirm that, in fact, the velopharynx is open during sound production. But sometimes physical measurements show that, surprisingly, the velopharynx is closed during sound production, despite what the musician is
feeling. Why the mismatch? A study of trombonists may have found the answer. By sensing changes in air pressure at the anterior nares, Bennett and Hoit (2013) discovered that some trombonists open the velopharynx at the beginning of expiration before the sound begins, and then close the velopharynx right as the sound starts. What they felt was correct: the velopharynx was open. But it was not open while they were actually playing. Sometimes the senses play tricks on us.
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Foundations of Speech and Hearing: Anatomy and Physiology140
(whether it be positive or negative) to prevent the velo- pharynx from being forced (blown or sucked) open. Thus, only a low compressive force is required to effect airtight velopharyngeal closure for an activity involv- ing low oral air pressure, whereas a high compressive force is required for an activity involving high positive oral air pressure.
Velopharyngeal-Nasal Acoustic Impedance
Acoustic (sound) impedance, like airway resistance, involves opposition to flow. However, it involves opposition to the flow of sound rather than to mass airflow. Thus, the acoustic impedance offered by the velopharyngeal-nasal apparatus pertains to the rapid to-and-fro bumping of air molecules in which each stays in a very restricted region and passes energy on to its neighbors. The opposition to acoustic flow is fre- quency dependent. As portrayed in Figure 4–18, acous- tic impedance influences flow propagation of sound waves (not breath). The acoustic impedance of concern here is that distributed across the velopharyngeal port, nasal cavities, and outer nose.
The velopharyngeal port can be adjusted to influ- ence the degree of acoustic coupling between the oral and nasal cavities. When the port is closed (see Figure 4–18A), the oral and nasal airways are separated. Thus, nearly all of the sound energy passes through the oral airway and mouth and the acoustic impedance looking
Oral cavity
Sound energy
Mouth
Outer nose
Nasal cavities
Sound energy
Velopharyngeal port
Velopharyngeal closure
Mouth
Nasal cavities
Sound energy
Outer nose
Velopharyngeal port
Oral cavity
A
B
C
FiGure 4–18. Oral-nasal sound wave propagation through the velopharyngeal-nasal pathway (velopharynx, nasal cavities, and outer nose) and oral pathway (oral cav- ity and mouth). The conditions shown are the velopharynx closed with sound routed through the oral pathway (A), the oral pathway closed with sound routed through the velo- pharyngeal-nasal pathway (B), and both pathways open so that sound is routed through both simultaneously (C).
Which Hunt
It is often stated that velopharyngeal incompe- tence or insufficiency allows air to pass into the nasal cavities, causing hypernasality. This is a misconception. Significant quantities of air can pass into the nasal cavities through the velopha- rynx during utterance without a perception of hypernasality. Also, hypernasality may be heard during utterance when no air is passing into the nasal cavities, such as when the covering tissue of a submucous cleft palate vibrates and excites the nasal cavities into sympathetic vibration. Flow of air into the nose does not cause hyper- nasality. In fact, hypernasality may be present when inspiratory speech is produced and airflow is passing through the nasal cavities in the opposite direction from usual. It’s instructive to go through written discussions about velo- pharyngeal dysfunction and see which authors get it right and which authors get it wrong. Think of it as sort of a “which” hunt.
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4 Velopharyngeal-Nasal Function and Speech Production 141
into the nasal cavities from their velopharyngeal end is nearly infinite. (A small amount of sound energy may be transmitted through the closed velopharynx via sympathetic vibration, such as when the velum acts like a drumhead.)
When the velopharyngeal port is open (see Fig- ures 4–18B and C), the oral and nasal cavities are free to exchange sound energy and interact with one another acoustically, and sound energy may pass through the nasal cavities to atmosphere. Changes in the size of the velopharyngeal port are important to determining how sound energy is divided between the oral and nasal cavities. Also important are configurations of the oral and nasal cavities themselves and the extent to which each impedes the flow of sound energy. In the case of the nasal part of the system, degree of engorgement of the nasal cavities and status of the anterior nares are relevant factors.
neural substrates of Velopharyngeal-nasal Control
Velopharyngeal-nasal movement is controlled by the nervous system, but the nature of that movement and the nature of its control differ with the activity being performed. That is, different parts of the nervous system take charge of different components of the velopharyngeal-nasal apparatus for different types of activities such as sneezing, blowing, swallowing, and speaking.
Although different parts of the central nervous system are responsible for the control of different velopharyngeal-nasal activities, control commands are, nonetheless, sent through the same set of cranial nerves to muscles. These nerves originate in the brain- stem and course outward to provide motor innerva- tion to the pharynx, velum, and outer nose. As shown in Table 4–1, motor innervation of the pharynx and velum is effected through the pharyngeal plexus, a network that includes fibers from cranial nerves IX (glossopharyngeal), X (vagus), and possibly XI (acces- sory). An exception is found in the case of the palatal tensor muscle, whose motor innervation is provided by cranial nerve V (trigeminal). There may also be addi- tional motor innervation to the pharynx and velum through cranial nerve VII (facial), especially related to the palatal levator and uvulus muscles. Motor innervation to the outer nose is effected by cranial nerve VII.
One might think that information about the motor nerve supply to different parts of the velopharyngeal- nasal apparatus would be straightforward and agreed upon. This is, indeed, the case for motor innervation to the outer nose, but not for motor innervation to the pharynx and velum. This is because the linkage between specific cranial nerves and the motor supply to specific muscles is equivocal in some cases (Cassell & Elkadi, 1995; Dickson, 1972; Moon & Kuehn, 2004) and because conducting research on motor nerve function in the velopharyngeal-nasal region of human beings is extremely difficult (Kuehn & Perry, 2008).
taBLe 4–1. Summary of the Motor and Sensory Nerve Supply to the Pharynx, Velum, and Outer Nose Components of the Velopharyngeal-Nasal Apparatus. Cranial nerves include V (trigeminal), VII (facial), IX (glossopharyngeal), X (vagus), and possibly XI (accessory).
INNERVATION
COMPONENT MOTOR SENSORY
Pharynxa IX, X, (XI)b V, VII, IX, X
Veluma IX, X, (XI) (except palatal tensor muscle, which is innervated by V)
V, VII, IX, X
Outer Nose VII V
aThere may be additional motor innervation from cranial nerve VII to certain muscles of the pharynx and velum, especially the palatal levator muscle and uvulus muscle (Shimokawa, Yi, & Tanaka, 2005). bThe branches of cranial nerve IX and X (and possibly XI) that innervate parts of the velopharynx are sometimes called the pharyngeal plexus.
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Foundations of Speech and Hearing: Anatomy and Physiology142
Sensory innervation to the pharynx and velum is effected through cranial nerves V, VII, IX, and X, and sensory innervation to the outer nose is effected through cranial nerve V. Neural information traveling along the sensory nerve supply from the pharynx, velum, and outer nose comes from receptors that respond to vari- ous types of stimuli, including mechanical stimuli. For example, receptors located in the mucosa of the velum and pharynx respond to light touch and receptors located in and near the velopharyngeal-nasal muscles relay information about muscle length and tension.
Much of incoming information from the velopha- ryngeal-nasal apparatus is not sensed or perceived. This seems to be especially true for the velopharyngeal portion of the apparatus. For example, the potential for sensing the position of the velum in space (propriocep- tion) and its movement (kinesthesia) is believed to be rudimentary or nonexistent. Empirical evidence for this can be found in studies in which normal speakers have been shown to have difficulty controlling velo- pharyngeal movements voluntarily (Ruscello, 1982; Shelton, Beaumont, Trier, & Furr, 1978). Thus, it seems likely that control of the velopharyngeal apparatus relies more heavily on other types of information, such as that associated with the sensing of air pressure and airflow (Liss, Kuehn, & Hinkle, 1994; Warren, Dalston, & Dalston, 1990) and that associated with the sensing of the acoustic signal (Netsell, 1990) via cranial nerve VIII (auditory-vestibular).
Ventilation and Velopharyngeal-nasal Function
Recall from Chapter 2 that ventilation is the movement of air in and out of the pulmonary apparatus for the purpose of gas exchange. This movement of air can be routed through the nose, the mouth, or both.
Resting tidal breathing usually occurs through the nose alone. This may seem somewhat counterintui- tive, given that the airway resistance through the nasal pathway is much greater than through the oral path- way. Nevertheless, the nasal route typically prevails. This is because it provides advantages for both inspi- ration and expiration. Advantages of nasal inspiration are that it converts the temperature of incoming air to that of the body, increases the humidity of incoming air, and filters dust, bacteria, and other contaminants from the incoming air before they reach the lungs and lower airways. An advantage of nasal expiration is that it helps slow the flow of expired air to ensure adequate alveolar gas exchange (Hairfield, Warren, Hinton, & Seaton, 1987) by providing an additional braking mechanism (Jackson, 1976) to accompany the laryngeal
braking mechanism that also serves to slow expiration (Gautier, Remmers, & Bartlett, 1973).
Although nasal breathing is the norm, there are times it becomes necessary to switch to mouth breath- ing (or combined mouth and nose breathing) to main- tain adequate ventilation. This occurs when the nasal pathway resistance becomes too high due to high air flow, nasal pathway constriction, or both. Interest- ingly, the magnitude of resistance that leads to switch- ing from solely nasal breathing to nasal-oral breathing turns out to be slightly lower than the resistance value that leads to the sensation of breathing discomfort (Warren, Hairfield, Seaton, Morr, & Smith, 1988; War- ren, Mayo, Zajac, & Rochet, 1996). This means that the switch from nasal breathing to oral–nasal breathing occurs before any awareness of breathing difficulty.
the masked man’s nose
Nose masks are often used in research and clinical endeavors. Such masks must be sealed airtight against the face so that air doesn’t leak around their edges. But therein lies a potential problem. How the face gets compressed beneath the edges of a mask can influence how air moves through the outer nose. Try the follow- ing: breathe in and out through your nose to experience your usual nasal resistance to airflow. Next, touch your face below both your eyes and slowly slide that skin toward the middle of your face — but don’t touch your outer nose. Notice how it gets harder to breathe when you do this. How your facial skin gets “scrunched” greatly influences your nasal resistance, even though you may not actually touch your outer nose. The same is true for how you position a mask on someone else. Be careful. Don’t scrunch the skin around the outer nose. Otherwise, you may raise nasal resistance to airflow.
VeLopHarynGeaL-nasaL FunCtion anD speeCH proDuCtion
The velopharyngeal-nasal apparatus adjusts the oral– nasal distribution of aeromechanical and acoustic ener- gies during speech production. For the production of oral speech sounds, the velopharyngeal valve is usually closed and aeromechanical and acoustic energies are channeled through the oral cavity (mouth). In contrast, for the production of nasal speech sounds, the velopha-
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4 Velopharyngeal-Nasal Function and Speech Production 143
rynx is open and aeromechanical and acoustic energies are channeled through the nasal cavities (nose).
The velopharyngeal-nasal apparatus has two important roles during speech production. One is to manage the airstream to produce oral consonant sounds, that require high oral pressure. Such manage- ment requires that the velopharynx be closed, or nearly so, and that aeromechanical energy be directed through the oral channel. The other role is to manage the flow of acoustic energy into the oral and nasal cavities. This is important for the production of vowels and both oral and nasal consonants.
This section focuses on a series of topics perti- nent to velopharyngeal-nasal function and speech production. These include consideration of sustained utterances and running speech activities, followed by separate discussions about the influences of gravity, development, age, and sex on velopharyngeal-nasal function in speech production.
Velopharyngeal-nasal Function and sustained utterances
Sustained vowels and consonants are usually produced with relatively stable configurations of the velopharyn- geal-nasal apparatus. Observations are typically made of the velopharyngeal portion of the apparatus.
Velopharyngeal function for sustained vowels has been studied mainly through the use of x-ray and aero- mechanical techniques. Observations have shown that the velum moves upward and backward toward the posterior pharyngeal wall in anticipation of vowel pro- duction (Bzoch, 1968; Lubker, 1968; Moll, 1962). At the same time, the lateral pharyngeal walls move inward1 and the posterior pharyngeal wall may move forward slightly (Iglesias, Kuehn, & Morris, 1980). The velum is usually elevated maximally in its midportion dur- ing vowel production and contact with the posterior pharyngeal wall (if it occurs) is typically achieved by velar tissue that is approximately two-thirds of the distance from the hard palate to the uvula (Graber, Bzoch, & Aoba, 1959). There is also a tendency for the velum to be elevated to a higher position when sus-
tained vowels are produced at higher vocal effort levels (Tucker, 1963).
Airtight closure of the velopharyngeal port may or may not occur during sustained vowel production. The probability of airtight closure favors high vowels (such as /i/ in peek) over low vowels (such as /ae/ in cat). For example, Moll (1962), in an x-ray motion picture study of the velopharynx in young adults, found some were opening the velopharyngeal port during less than 15% of high vowel productions and nearly 40% of low vowel productions.
Whether or not airtight velopharyngeal closure is achieved, high vowels and low vowels contrast in still other ways. Compared to low vowel production, high vowel production is associated with: (a) greater velar height, (b) greater extent of velar contact with the posterior pharyngeal wall when the two surfaces are in apposition, and (c) smaller distance between the velum and the posterior pharyngeal wall when closure is not complete (Iglesias et al., 1980; Lubker, 1968; Moll, 1962). High vowel production also involves greater velopha- ryngeal sphincter compression (closing force) than low vowel production when velopharyngeal closure is complete (Gotto, 1977; Kuehn & Moon, 1998; Moon, Kuehn, & Huisman, 1994a; Nusbaum, Foly, & Wells, 1935). Velar height differences during sustained vowel productions are relatively strongly correlated with the electrical activity of the palatal levator muscles (Bell-Berti, 1976; Fritzell, 1969; Lubker, 1968). Less than perfect correlations may relate to partial influences of other muscles involved in trading relationships with the palatal levator muscle in velar height adjustments (Fritzell, 1969; Kuehn et al., 1982).
Two possible mechanisms have been proposed to account for the differences observed in velar height between high and low vowel productions. These are portrayed in Figure 4–19. One is that the velum elevates to different degrees because of anatomical constraints imposed through interconnections to struc- tures below (Harrington, 1944; Kaltenborn, 1948; Lub- ker, 1968; Moll, 1962). Likely candidates include the glossopalatine and pharyngopalatine muscles that have originating attachments from below the velum. The glossopalatine muscle is considered to be the more
1 The suggestion has been made (Dickson & Dickson, 1972) that the palatal levator muscles are responsible for both elevation of the velum and inward movements of the lateral pharyngeal walls. Those in support of this suggestion contend that inward movements of the lateral pharyngeal walls occur in a region of the pharynx above the fiber course of the superior constrictor muscles (Honjo, Harada, & Kumazasa, 1976; Isshiki, Harita, & Kawano, 1985). A contrary viewpoint is that elevation of the velum and inward movements of the lateral pharyngeal walls are simply coordinated actions of the palatal levator muscles (to elevate the velum) and the superior constrictor muscles (to move the lateral pharyngeal walls inward). Those in support of this viewpoint contend that inward movements of the lateral pharyngeal walls occur below the velar eminence associated with insertion of the palatal levator muscles into the velum (Shprintzen, McCall, Skolnick, & Lenicone, 1975; Skolnick, 1970; Skolnick et al., 1973) and that the timing of movements of the velum and lateral pharyngeal walls are poorly correlated during speech production in normal individuals (Iglesias et al., 1980). We support this latter viewpoint in our description of velopharyngeal- nasal function and point the interested reader to Moon and Kuehn (2004) for further discussion on this topic.
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Foundations of Speech and Hearing: Anatomy and Physiology144
important of the two candidates. The hypothesis is that the glossopalatine muscle tethers the velum so that low vowels (involving low tongue positions) restrict elevation of the velum and lead to lesser degrees of closure of the velopharyngeal port. The influence
of tethering is less for high vowels (involving high tongue positions) because less restriction is placed on velar elevation.
The second mechanism proposed to account for velar height differences between high and low vowel
High vowels
Minimum mechanical tethering of velum
from below
Higher oral acoustic impedance
Low vowels
Smaller velopharyngeal opening
Non-nasal speech
Lower oral acoustic impedance
Larger velopharyngeal opening
Non-nasal speech
Maximum mechanical tethering of velum
from below
Tongue (Glossopalatine)
Pharynx (Pharyngopalatine)
Or
Or
FiGure 4–19. Possible mechanisms to explain why high vowels, when compared to low vowels, are associated with a greater velar height and greater contact between the velum and posterior pharyngeal wall (or smaller distance between them if there is no contact). One possible mechanism (left side of figure) relates to the tethering of the velum to struc- tures below through connections created by the glossopalatine muscle. Another possible mechanism (right side of figure) relates to the acoustic product and the need to ensure that the vowel is not perceived as nasal.
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4 Velopharyngeal-Nasal Function and Speech Production 145
productions has an acoustic-perceptual basis. That is, it may be that the velum elevates to different degrees because of acoustic requirements involved in ensur- ing that the utterance is not perceived as nasal (Cur- tis, 1968; Lubker, 1968; Moll, 1962). This speculation is based on the results of electrical analog studies of the nasalization of vowels conducted by House and Ste- vens (1956) and more recently with a computational speech production model by Bunton and Story (2012). Both studies demonstrated that less nasal coupling (velopharyngeal opening) is required to produce the auditory-perceptual judgment of nasal quality on high vowels than on low vowels. Thus, the velar height dif- ferences observed for high and low vowels could be purposive adjustments to control the degree of nasal- ization in the face of different tongue adjustments that influence the flow of acoustic energy through the oral and nasal cavities. In effect, at any given moment the particular shape of the oral and pharyngeal cavities (primarily due to position of the tongue) influences how the velopharynx must adjust to maintain the per- ception of non-nasal speech.
Velopharyngeal function has also been exam- ined during sustained consonant production. The consonants most often studied have been fricatives, especially /s/ and /z/, and nasals /m/ and /n/. Aeromechanical studies of nasal airflow during speech production (Hoit, Watson, Hixon, McMahon, & John- son, 1994; Thompson & Hixon, 1979) revealed airtight velopharyngeal closure on all sustained /s/ produc- tions and essentially all sustained /z/ productions of children and adults ranging in age from 3 to 97 years. Airtight closure of the velopharyngeal port (shown in Figure 4–14 and 4–18A) is clearly a priority on speech sounds that rely on management of the oral airstream for their production. Support for this is also found in an x-ray study (Iglesias et al., 1980) wherein sustained /z/ production had a higher velar elevation and more forward displacement of the posterior pharyngeal wall than did any of four sustained vowels that were studied.
Sustained nasal consonants are produced with large openings of the velopharyngeal port, as illus- trated in Figure 4–20. The position of the velum is the same (or slightly higher) for sustained /m/ produc- tions (Lubker, 1968) and sustained /n/ productions (Iglesias et al., 1980) compared to that observed for resting tidal breathing through the nose, and palatal levator muscle activity is not discernible via electro- myographic recordings (Lubker, 1968). Predictably, sustained nasal consonant productions are accom- panied by substantial nasal airflow (Hoit et al., 1994; Thompson & Hixon, 1979).
Velopharyngeal-nasal Function and running speech activities
Running speech activities require rapid adjustments of the velopharyngeal-nasal apparatus. A few minutes spent watching x-ray or real-time magnetic resonance imaging (MRI) recordings of running speech activities reveals that velopharyngeal articulation is every bit as fast and intricate as are movements of the mandible, tongue, and lips. In fact, velar elevating and lowering gestures can each occur within a time interval of about 1/10 of a second (Kuehn, 1976). During running speech production, the velopharyngeal port closes to various degrees for oral speech sounds and opens to various degrees for nasal speech sounds. The precise pattern of opening and closing and the degree to which the velopharyngeal port is opened or closed relate to the nature of the speech sounds being spoken, the influ- ence of surrounding sounds on a current sound being spoken, and the rate at which they are produced (Kent et al., 1974).
When consonants and vowels are combined, as they are in running speech activities, primacy of control of the velopharyngeal-nasal apparatus is vested in con- sonant productions. This is because the production of many consonant elements relies heavily on appropriate management of the airstream. Sacrificing the aerome- chanical requirements of these consonants by opening
Velum
FiGure 4–20. Velar position for sustained nasal conso- nant production. The velum is lowered to allow airflow and acoustic energy to pass through the velopharynx.
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Foundations of Speech and Hearing: Anatomy and Physiology146
the velopharynx may result in sacrificing the intel- ligibility of speech. In contrast, sacrificing closure for vowel productions may increase nasalization but has only a minimal affect on speech intelligibility. Those consonant elements that rely most on aeromechanical management of the airstream are often referred to as the pressure consonants because they are characteristi- cally produced with high oral air pressure and little or no velopharyngeal opening. Stop-plosive, fricative, and affricate speech sounds (see Chapter 5) are catego- rized as pressure consonants. In contrast, nasal conso- nants are produced with low oral air pressure and a relatively wide-open velopharyngeal port.
The control of the velopharyngeal-nasal appara- tus during running speech production is not simply a sequencing of separate and independent position and movement patterns for different speech sounds. To use an analogy, velopharyngeal adjustments for sequences of speech sounds are not like sequences of keyboard characters that are produced when each is called on to make an appearance (Hixon & Abbs, 1980). Rather, the position and movement patterns for two or more speech sounds may occur simultaneously, such that their productions actually overlap and intermingle. This is what was meant when it was stated above that the patterning of opening and closing of the velopha- ryngeal port for a particular sound is not only deter- mined by the requirements for that sound, but also by the influence of surrounding sounds. Part of this has to do with how the brain prepares in advance for velo- pharyngeal-nasal adjustments and part has to do with how the mechanical-inertial properties of the velopha- ryngeal-nasal apparatus influence its behavior. More is said about these principles in Chapter 5.
Underlying the assembling of velopharyngeal- nasal positions and movements is the principle that consonants influence the velopharyngeal-nasal adjust-
ments of all speech sounds (consonants and vowels) within their interval of preparation. The precise influ- ence depends on both the type of consonant and type of vowel. For example, the preparation period for oral consonants results in smaller velopharyngeal port openings for vowels that precede them, whereas the preparation period for nasal consonants results in larger velopharyngeal port openings for vowels that precede them (Warren & DuBois, 1964). Furthermore, when a nasal consonant is preceded by two consecu- tive vowels, the opening of the velopharyngeal port for the nasal consonant is initiated during the produc- tion of the first vowel in the sequence (Moll & Daniloff, 1971). Even the presence of a word boundary within a sequence does not affect this observation, although velar lowering may be delayed somewhat at marked junctural boundaries (McClean, 1973). The interac- tions between different speech sound adjustments of the velopharyngeal-nasal apparatus condition the posi- tion and movement patterns observed such that, at any instant, the configuration of the apparatus may con- tain evidence of events that are coming and events that have already taken place.
Understandably, the study of velopharyngeal-nasal function for speech production has focused on the expi- ratory phase of the breathing cycle, the phase of the cycle during which speech is produced. Nevertheless, the velopharyngeal-nasal apparatus also appears to play an important role during the inspiratory phase of the speech breathing cycle. Running speech breathing usu- ally demands quick inspirations to minimize interrup- tions to the flow of speech, and quick inspirations require a low resistance pathway. The best way to create such a low resistance pathway is to abduct the lips and open the velopharynx simultaneously. And this is, in fact, what people do. Thus, in contrast to resting tidal breathing, during which inspirations are typically routed through
playing by Her own rule
She was a young woman with a profound bilateral hearing loss. She’d received intensive behavioral therapy for imprecise articulation, but essen- tially no progress was being made. A puzzled speech-language pathologist made the referral. What was preventing improvement in speech? The answer was found in a recording of nasal airflow. A large burst of airflow was found to accompany each segment of speech that included a voiceless consonant. The young woman had apparently developed a production rule that said, “Only close your velopharynx for speech when your voice is on.” It turned out to be a rule that could be changed by displaying nasal airflow for her to monitor on a storage oscilloscope so that she could see her rule in action and adopt a more appropriate one with some guidance. Her velopha- rynx cooperated and her articulation improved.
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4 Velopharyngeal-Nasal Function and Speech Production 147
the nose exclusively, inspirations are routed through both the mouth and nose during speaking (Lester & Hoit, 2014). This not only allows for quick inspirations, but may also preserve some of the benefits of nasal inspira- tions, such as air filtration and humidification.
Gravity and Velopharyngeal-nasal Function in speech production
Velopharyngeal-nasal function changes with changes in spatial orientation, primarily because of the influ- ence of gravity. Each time the velopharyngeal-nasal apparatus is reoriented within a gravity field, alternate mechanical solutions are required to meet the goals for adjusting the velopharyngeal port. Reorientation in this context can result from a change in body position. For example, the usual upright (standing or seated) body position can be changed to semirecumbent, supine, prone, side-lying (left and right lateral), and head down positions, among others. Correspondingly, the orientation of the velopharyngeal-nasal apparatus will follow these changes.
Certain predictions can be made about the influ- ence of body position on the velopharyngeal-nasal
apparatus. These predictions as they relate to the velum are illustrated in Figure 4–21 for the upright and supine body positions. When the apparatus is in an upright position, the pull of gravity tends to lower the velum. This means that muscle force exerted to elevate the velum must overcome this pull, whereas muscle force exerted to lower the velum augments this pull. When in the supine body position, gravity acts to pull the velum toward the posterior pharyngeal wall. Thus, in supine, muscle force associated with movement of the velum toward the posterior pharyngeal wall augments the pull of gravity, and muscle force associated with moving the velum away from the posterior pharyngeal wall must overcome the pull of gravity.
Moon and Canady (1995) conducted a study of the effects of body position (and, therefore, gravity) on velopharyngeal muscle activity during speech production. They studied the activation levels (using electromyography) of the palatal levator and pha ryngopalatine muscles in upright and supine body positions and hypothesized that activation would be modulated by gravitational effects. Lower peak activa- tion levels were observed in the supine body position for the palatal levator muscle, suggesting that less acti- vation was required when the pull of gravity was in the
SupineUpright
Tongue
Tongue
Velum
Velum
FiGure 4–21. Predicted influences of body position on the velum. In upright body positions, gravity exerts a downward pull on the velum, whereas in the supine body position gravity pulls the velum toward the posterior pharyngeal wall. Thus, gravity counteracts the efforts of the palatal levator muscles in upright and augments them in supine.
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Foundations of Speech and Hearing: Anatomy and Physiology148
same direction (toward the posterior pharyngeal wall). Also, the activation level of the pharyngopalatine muscle was usually greater in the supine body position where the pull of gravity was counter to movement of the velum away from the posterior pharyngeal wall. Overall, the observations of Moon and Canady gener- ally support the notion that levels of muscle activity in the velum are modulated in relation to the direction of the pull of gravity, with the effect being robust in the palatal levator muscle.
Reorientation of the velopharyngeal-nasal appa- ratus in space is not restricted to changes in body position. Reorientation can also mean that the body is maintained in a fixed position and the head is moved about different axes, thereby changing the spatial ori- entation of the velopharyngeal-nasal apparatus. For example, the head can be pitched about a lateral axis, rolled about a longitudinal axis, and yawed about a vertical axis. Simultaneous adjustments can also be made through more than one axis (pitching the head upward and yawing it to the right at the same time).
Rotation of the head about a lateral axis is an espe- cially common activity that influences the spatial orien- tation of the velopharyngeal-nasal apparatus (nod your head yes to this statement). Full flexion and full exten- sion of the neck (head rotated forward and backward, respectively) delimit the range of possible orientations associated with head rotation. Rotation through this range places maximally contrasting gravitational forces on the velopharyngeal-nasal apparatus, especially the velum. When the head is rotated downward from its usual position (toward a position in which the mandi- ble would rest on the rib cage wall), the pull of gravity on the velum is in a direction that tends to pull it away from the posterior pharyngeal wall. In contrast, when the head is rotated upward from its usual position (toward a position in which the tip of the nose is maxi- mally elevated), the pull of gravity on the velum is in a direction that tends to pull it toward the posterior pha- ryngeal wall. Whereas reorientation of the velopharyn- geal-nasal apparatus is not noticeable to most people, it may have a profound effect on those with borderline velopharyngeal competence. For example, in someone with a neuromotor-based weakness of the palatal leva tor muscles, rotation of the head upward may enhance movement of the velum toward the posterior pharyn- geal wall and, thereby, improve velopharyngeal-nasal function for speech production. In contrast, rotation of the head downward may do just the opposite.
Gravitational influences also affect the function of the nasal cavities. For example, it has been shown that nasal patency decreases and nasal airway resistance increases in downright as compared to upright body positions (Rudcrantz, 1969). This change in patency
appears to relate to vascular changes that cause nasal congestion (Hiyama, Ono, Ishiwata, & Kuroda, 2002).
Development of Velopharyngeal-nasal Function in speech production
The infant’s velopharyngeal-nasal apparatus is not just a small version of the adult’s apparatus, but differs in its configuration and spatial relationships to surround- ing structures. Several anatomical features and devel- opmental changes in those features are relevant to how the velopharyngeal-nasal apparatus functions in infants and children. (See Chapter 5 for further discussion of the development of upper airway structures.)
At birth, the larynx is located high within the neck, and the velum and epiglottis are approximated (Kent & Murray, 1982). Around 4 to 6 months of age, the velum and epiglottis separate (Sasaki, Levine, Laitman, & Crelin, 1977) as the larynx moves from the level of the first cervical vertebra to the level of the third cervical vertebra. This downward movement is accomplished primarily by rapid growth in the vertical dimension from about 4 cm in the pharynx of the newborn (Cre- lin, 1973) to approximately three times that length in the adult pharynx (Sasaki et al., 1977). During that same period, the hard and soft palates grow quickly, with the hard palate growing somewhat more quickly than the soft palate and the growth rate of both becom- ing more gradual after 2 years of age (Vorperian et al., 2005). These developmental changes affect the geom- etry and mechanical effectiveness of certain muscles. For example, as the palates grow, the orientation of the paired palatal levator muscle changes in ways that improve their mechanical advantage for elevating the velum (Fletcher, 1973).
Because the infant velum and epiglottis are approx- imated early in life, it is often assumed that infants are “obligate nasal breathers” (meaning that they breathe through the nose by necessity). However, this is not true. The preponderance of evidence indicates that most infants can breathe through the mouth when necessary. Specifically, when the anterior nares are occluded, healthy infants open the mouth and use the oral airway for breathing (Miller et al., 1985; Roden- stein, Perlmutter, & Stanescu, 1985). Therefore, the term preferential nasal breather is more appropriate to describe the predominant (rather than exclusive) use of the nasal airway for breathing in infants.
The birth cry is the first utterance for most human newborns. X-ray images of this first utterance have shown that it is made with an open velopharynx (Bosma, Truby, & Lind, 1965). Acoustic and percep-
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4 Velopharyngeal-Nasal Function and Speech Production 149
tual studies of infant vocalizations during the first few months of life have suggested that the velopharynx continues to be open during cry (Wasz-Hockert, Lind, Vuorenkoski, Partanen, & Valanne, 1964) and noncry vocalizations up to about 4 months of age (Buhr, 1980; Hsu, Fogel, & Cooper, 2000; Kent & Murray; 1982; Oller, 1986). Aeromechanical studies (Bunton & Hoit, 2016; Thom, Hoit, Hixon, & Smith, 2006) have shown that infants close the velopharynx at least occasionally for noncry vocalizations as early as 2 months of age and that the frequency of velopharyngeal closure for noncry oral sound production increases up to about 18 months of age. Once children reach the age of 3 years, the velopharynx closes for oral utterances and opens for nasal sound production (Thompson & Hixon, 1979; Zajac, 2000).
The temporal characteristics of velopharyngeal- nasal function during speech production in children ages 3 to 16 years have also been studied using aero- mechanical techniques (Leeper, Tissington, & Munhall, 1998; Zajac, 2000; Zajac & Hackett, 2002). The speech samples most often studied were nasal consonant– stop consonant combinations, which required rapid transitions between velopharyngeal opening and velopharyngeal closure. Leeper et al. reported a ten- dency toward shorter durations in temporal variables
with increasing age, but with the children generally performing similarly to the adults studied by Warren, Dalston, Trier, and Holder (1985). Subsequently, Zajac and then Zajac and Hackett reported differences in patterns of timing in the aeromechanical segments of speech produced by children and adults, with adults exhibiting shorter segments and less temporal variabil- ity than children.
Although airtight velopharyngeal closure is used early in childhood for oral speech sound produc- tion, the means for achieving this closure may change across childhood. One example relates to children who develop enlarged lymphoid tissue masses in the naso- pharyngeal tonsils (adenoids). These tonsils typically grow during the first decade of life and then begin to atrophy (Jaw, Sheu, Liu, & Lin, 1999; Subtelny & Koepp-Baker, 1956) until by adulthood they have fully atrophied, as illustrated in Figure 4–22. Against this background of anatomical change, velopharyngeal clo- sure must go through a slow reorganization in those children who have been accomplishing closure through abutment of the velum and walls of the pharynx against the enlarged adenoidal tissue. This accommo- dation is obviously successful given the continuation of airtight velopharyngeal closure during the normal developmental schedule, but it may be interrupted if
Nasopharyngeal tonsil
Adult Teenager Child
FiGure 4–22. Changes in nasopharyngeal tonsil mass during development. The nasopharyngeal tonsil is large in children and atrophies with age. The velopharyngeal structures accommodate to these changes to achieve velopharyngeal closure.
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Foundations of Speech and Hearing: Anatomy and Physiology150
an adenoidectomy (removal of the adenoids) is per- formed in a child who is at risk for velopharyngeal problems (Andreassen, Leeper, MacRae, & Nicholson, 1994; Finkelstein, Berger, Nachmani, & Ophir, 1996; Morris, 1975; Siegel-Sadewitz, & Shprintzen, 1986).
age and Velopharyngeal-nasal Function in speech production
Aging affects the mature velopharyngeal-nasal appa- ratus as it does other parts of the body. For example, the pharyngeal muscles weaken with age and the pha- ryngeal lumen enlarges (Zaino & Benventano, 1977), sensory innervation declines (Aviv et al., 1994), and muscle bulk and bone density decrease in this region
and elsewhere (Fremont & Hoyland, 2007). Such changes would seem to have the potential to alter velo- pharyngeal-nasal function for activities such as speech production.
Hutchinson, Robinson, and Nerbonne (1978) were the first to examine the potential influence of age on velopharyngeal-nasal function in speech production by measuring nasalance, an acoustic measurement of the quotient of nasal sound pressure level to nasal + oral sound pressure level. They found that older men and women exhibited higher average nasalance val- ues during reading compared to younger men and women. This finding was interpreted as evidence that velopharyngeal function for speech production dete- riorates with age. Nevertheless, acoustic evidence to the contrary (Seaver, Dalston, Leeper, & Adams, 1991)
When is a Bad nose Good and a Good nose Bad?
This chapter stresses the functional unity of the normal velopharyngeal- nasal apparatus. This unity is often even better illustrated in an abnormal velopharyngeal-nasal apparatus. Not all speakers with significant velopha- ryngeal openings during oral consonant productions are destined to exhibit significant speech problems. With the velopharynx and nose being in mechanical series (being in line), an abnormally blocked nose may actually counteract an abnormally opened velopharynx. That is, a bad nose can be a good thing for speech, even if not for breathing. Conversely, a good nose can be a bad thing for speech when there is significant velopharyngeal impairment. The surgeon who attempts to “clean up” a bad nose and does not take into account the status of the velopharynx, will sometimes figure this out after the fact when confronted with a child whose speech is worse after surgery.
He’s an old smoothie
He was a distinguished looking white-haired grandfather. He agreed to be examined by graduate students learning to administer an examination for velopharyngeal-nasal function. Students had been assigned different parts of the examination and told to practice the administration of their part on at least half a dozen people so they could get “calibrated.” One student who had dutifully practiced on a group of her peers, proceeded to ask the gentle- man to open his mouth while she turned on a flashlight and looked in. She methodically looked at structures and made comments to the class as she went along. When she shined the light on the gentleman’s hard palate, she paused briefly and said to him, “That’s the smoothest hard palate I’ve ever seen.” He smiled and said back, “That’s a denture, young lady.” And so it was. He took it out and showed it to the class. The moral of this story is don’t just practice on your classmates.
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4 Velopharyngeal-Nasal Function and Speech Production 151
and aeromechanical studies (using measures of airflow and air pressure) confirmed that velopharyngeal func- tion does not deteriorate with age by showing that the velopharynx is essentially airtight during oral utter- ance production in men and women as old as 97 years (Hoit et al., 1994; Zajac, 1997).
What could explain the lack of agreement between the conclusions of Hutchinson et al. (1978) — that velo- pharyngeal function for speech production deteriorates with age — and those of Hoit et al. (1994) and Zajac (1997) — that velopharyngeal function does not change with age? One possible explanation is that measures of nasalance (an acoustic measure) do not necessar- ily reflect velopharyngeal function per se, but can be influenced by other factors that change with age. For example, confounding variables could include: (a) an increase in the sympathetic transfer of acoustic energy from the oral cavity to the nasal cavities attendant to changes in the density of palatal structures with age (Tomoda, Morii, Yamashita, & Kumazawa, 1984), (b) a change in the spectral content of speech sounds associ- ated with known age-related decreases in vocal tract formant frequencies (Endres, Bambach, & Flosser, 1967), and (c) the use of smaller mouth openings dur- ing oral utterances by older individuals that would be consistent with differences in characteristic mandibular movement in older compared to younger individuals (Karlsson & Carlsson, 1990). That is, it is quite possi- ble that an elderly person could demonstrate elevated nasalance values, even when the velopharynx is closed airtight.
sex and Velopharyngeal-nasal Function in speech production
Sex makes a difference when it comes to the size of the velopharyngeal-nasal apparatus. For example, men, when compared to women, have longer pha- rynges (Fitch & Giedd, 1999), longer palatal levator muscles (Bae, Kuehn, Sutton, Conway, & Perry, 2011; Ettema, Kuehn, Perlman, & Alperin, 2002), longer hard palates (Bae et al. 2011), larger soft palates (Kuehn & Kahane, 1990), and longer noses (Zankl, Eberle, Molinari, & Schinzel, 2002). But do these differences influence velopharyngeal-nasal function for speech production?
There have been many studies comparing velo- pharyngeal function during speech production in men and women. These include studies that used x-ray techniques to track velar movement (Bzoch, 1968; Iglesias et al., 1980; Kuehn, 1976; McKerns & Bzoch, 1970; Seaver & Kuehn, 1980), electromyography to
record velar muscle activity (Seaver & Kuehn, 1980), and air pressure and airflow measures to determine velopharyngeal status (open vs closed) and orifice size (Andreasson, Smith, & Guyette, 1992; Hoit et al., 1994; Thompson & Hixon, 1979; Zajac & Mayo, 1996). Although their findings revealed some sex-related dif- ferences, they were small, idiosyncratic, or contradic- tory between studies. The only consistent sex-related difference was that the magnitude of airflow during nasal productions was greater in men than women. This is to be expected, given that men have larger air- ways than women.
Thus, the evidence indicates that men and women differ in certain details of velopharyngeal-nasal func- tion in speech production. However, it is not clear that these differences make a difference functionally or in their application to clinical concerns (McWilliams, Morris, & Shelton, 1990).
reVieW
The velopharyngeal-nasal apparatus is located within the head and neck, and comprises a system of valves and air passages that interconnects the throat and atmosphere through the nose.
The velopharyngeal-nasal apparatus includes the pharynx, velum, nasal cavities, and outer nose.
Forces of the velopharyngeal-nasal apparatus are of two types — passive and active, the former arising from several sources and the latter arising from mus- cles distributed within different parts of the velopha- ryngeal-nasal apparatus.
Muscles of the pharynx include the superior constrictor, middle constrictor, inferior constric tor, salpingopharyngeus, stylopharyngeus, and pala topharyngeus.
Muscles of the velum include the palatal leva tor, palatal tensor, uvulus, glossopalatine, and pharyngopalatine.
Muscles of the outer nose include the levator labii superioris alaeque nasi, anterior nasal dilator, poste rior nasal dilator, nasalis, and depressor alae nasi.
Movements of the pharynx enable its lumen to be changed along its length, either by constriction or dila- tion at different sites.
Movements of the velum involve shape changes of the structure and are mainly along an upward-back- ward or downward-forward path.
Movements of the outer nose influence the cross- sections of the anterior nares and are involved in breathing events and the signaling of emotions.
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Foundations of Speech and Hearing: Anatomy and Physiology152
Adjustments of the velopharyngeal-nasal appara- tus can influence the degree of coupling between the oral and nasal cavities and between the nasal cavities and atmosphere.
Closure of the velopharyngeal port can be achieved through a variety of movement strategies that involve different actions or combinations of actions of the velum, lateral pharyngeal walls, and posterior pha- ryngeal wall, strategies that are conditioned by velo- pharyngeal anatomy.
Closing and opening adjustments of the velopha- ryngeal port are controlled by different factors, with closing being controlled by muscular forces and open- ing being controlled by passive forces and muscular forces.
Adjustments of the anterior nares are involved in different activities and play a prominent role in breath- ing to resist the tendency of the outer nose to collapse in response to low pressures in its lumina.
The control variables of velopharyngeal-nasal function include airway resistance offered by the velopharyngeal-nasal apparatus, muscular pressure exerted by the velopharyngeal sphincter to maintain closure, and acoustic impedance in opposition to the flow of sound energy.
Different parts of the nervous system are respon- sible for the control of different components of the velopharyngeal-nasal apparatus and different activi- ties, with motor and sensory innervation being effected mainly through cranial nerves.
The warming, moistening, and filtering aspects of nasal function are important to health, and nasal breathing prevails until airway resistance becomes excessive, whereupon a switch is made to oral-nasal breathing.
The role of velopharyngeal-nasal function in speech production is to control the degree of coupling between the oral and nasal cavities and between the nasal cavities and atmosphere.
The velopharynx is active during sustained utter- ances, the patterning depending on the speech sound being produced, and with high vowels showing greater velar height, greater velar contact with the posterior pharyngeal wall, and greater velopharyngeal sphincter compression than low vowels.
Running speech activities involve combining consonants and vowels with primacy of control being vested in consonant productions, especially those that are associated with high oral pressure and little or no opening of the velopharyngeal port.
Position and movement patterns of the velopha- ryngeal-nasal apparatus may reflect the occurrence of two or more speech sounds simultaneously, such that
their productions overlap and intermingle and show evidence of how the brain prepares in advance for velo- pharyngeal-nasal adjustments and how the mechanical properties of the velopharyngeal-nasal apparatus influ- ence its behavior.
Gravity has effects on velopharyngeal-nasal func- tion that are manifested through reorientation of the position of the body or rotation of the head about dif- ferent axes, and are attributed to mechanical and car- diovascular factors.
Velopharyngeal-nasal closure for speech produc- tion develops gradually during infancy and appears to be relatively stable by 18 months of age with continu- ing modifications of temporal events related to velo- pharyngeal closure during childhood.
There is no credible evidence that velopharyngeal- nasal function for speech production changes with age in the mature velopharyngeal-nasal apparatus.
The sex of the speaker appears to have an influ- ence on certain details of velopharyngeal-nasal func- tion during speech production, but it is not clear that these differences are functionally important or that they are relevant to clinical concerns.
reFerenCes
Andreassen, M., Leeper, H., MacRae, D., & Nicholson, I. (1994). Aerodynamic, acoustic, and perceptual changes following adenoidectomy. Cleft Palate-Craniofacial Journal, 31, 264–270.
Andreassen, M., Smith, B., & Guyette, T. (1992). Pressure-flow measurements for selected oral and nasal sound segments produced by normal adults. Cleft Palate-Craniofacial Journal, 29, 1–9.
Aviv, J., Martin, J., Jones, M., Wee, T., Diamond, B., Keen, M., & Blitzer, A. (1994). Age-related changes in pharyngeal and supraglottic sensation. Annals of Otology, Rhinology, and Lar- yngology, 103, 749–752.
Azzam, N., & Kuehn, D. (1977). The morphology of musculus uvulae. Cleft Palate Journal, 14, 78–87.
Bae, Y., Kuehn, D., Sutton, B., Conway, C., & Perry, J. (2011). Three-dimensional magnetic resonance imaging of velo- pharyngeal structures. Journal of Speech, Language, and Hear- ing Research, 54, 1538–1545.
Barsoumian, R., Kuehn, D., Moon, J., & Canady, J. (1998). An anatomic study of the tensor veli palatini and dilata- tor tubae muscles in relation to eustachian tube and velar function. Cleft Palate-Craniofacial Journal, 35, 101–110.
Bell-Berti, F. (1976). An electromyographic study of velopha- ryngeal function in speech. Journal of Speech and Hearing Research, 19, 225–240.
Bennett, K., & Hoit, J. (2013). Stress velopharyngeal incom- petence (SVPI) in collegiate trombone players. Cleft Palate- Craniofacial Journal, 50, 388–393.
EBSCOhost - printed on 10/23/2020 8:35 PM via CUNY LEHMAN COLLEGE. All use subject to https://www.ebsco.com/terms-of-use
4 Velopharyngeal-Nasal Function and Speech Production 153
Boorman, J., & Sommerlad, B. (1985). Levator palati and palatal dimples: Their anatomy, relationship and clinical significance. British Journal of Plastic Surgery, 38, 326–332.
Bosma, J., Truby, H., & Lind, J. (1965). Cry motions of the newborn infant. Acta Paediatrica Scandinavica, 163, 63–91.
Bridger, G. (1970). Physiology of the nasal valve. Archives of Otolaryngology, 92, 543–553.
Buhr, R. (1980). The emergence of vowels in an infant. Journal of Speech and Hearing Research, 23, 73–94.
Bunton, K. & Hoit, J. (2016, March). Velopharyngeal closure dur- ing the first 24 months of life in typically developing children. Poster presented at the Conference on Motor Speech, New- port Beach, CA.
Bunton, K., & Story, B. (2012). The relation of nasality and nasalance to nasal port area based on a computational model. Cleft Palate-Craniofacial Journal, 49(6), 741–749.
Bzoch, K. (1968). Variations in velar valving: The factor of vowel changes. Cleft Palate Journal, 5, 211–218.
Cassell, M., & Elkadi, H. (1995). Anatomy and physiology of the palate and velopharyngeal apertures. In R. Shprintzen & J. Bardach (Eds.), Cleft palate speech management: A multi- disciplinary approach (pp. 45–61). St. Louis, MO: Mosby.
Crelin, E. (1973). Functional anatomy of the newborn. New Haven, CT: Yale University Press.
Croft, C., Shprintzen, R., & Rakoff, S. (1981). Patterns of velo- pharyngeal valving in normal and cleft palate subjects: A multiview videofluoroscopic and nasendoscopic study. Laryngoscope, 91, 265–271.
Curtis, J. (1968). Acoustics of speech production and nasaliza- tion. In D. Spriestersbach & D. Sherman (Eds.), Cleft palate and communication (pp. 27–60). New York, NY: Academic Press.
Dickson, D. (1972). Normal and cleft palate anatomy. Cleft Palate Journal, 9, 280–293.
Dickson, D., & Dickson, W. (1972). Velopharyngeal anatomy. Journal of Speech and Hearing Research, 15, 372–381.
Endres, W., Bambach, W., & Flosser, G. (1967). Voice spec- trograms as a function of age, voice disguise, and voice imitation. Journal of the Acoustical Society of America, 49, 1842–1848.
Ettema, S., Kuehn, D., Perlman, A., & Alperin, N. (2002). Mag- netic resonance imaging of the levator veli palatini muscle during speech. Cleft-Palate-Craniofacial Journal, 39, 130–144.
Finkelstein, Y., Berger, G., Nachmani, A., & Ophir, D. (1996). The functional role of the adenoids in speech. International Journal of Pediatric Otorhinolaryngology, 34, 61–74.
Finkelstein, Y., Shapiro-Feinberg, M., Talmi, Y., Nachmani, A., DeRowe, A., & Ophir, D. (1995). Axial configuration of the velopharyngeal valve and its valving mechanism. Cleft Palate-Craniofacial Journal, 32, 299–305.
Fitch, W., & Giedd, J. (1999). Morphology and development of the human vocal tract: A study using magnetic reso- nance imaging. Journal of the Acoustical Society of America, 106, 1511–1522.
Fletcher, S. (1973). Maturation of the speech mechanism. Folia Phoniatrica, 25, 161–172.
Fremont, A., & Hoyland, J. (2007). Morphology, mechanisms and pathology of musculoskeletal ageing. Journal of Pathol- ogy, 211, 252–259.
Fritzell, B. (1963). An electromyographic study of the move- ments of the soft palate in speech. Folia Phoniatrica, 15, 307–311.
Fritzell, B. (1969). The velopharyngeal muscles in speech. Acta Otolaryngologica, Supplement. 250, 1–81.
Fritzell, B. (1979). Electromyography in the study of the velo- pharyngeal function — A review. Folia Phoniatrica, 31, 93–102.
Gautier, H., Remmers, J., & Bartlett, D. (1973). Control of the duration of expiration. Respiration Physiology, 18, 205–221.
Gotto, T. (1977). Tightness in velopharyngeal closure and its regulatory mechanism. Journal of the Osaka University Den- tal Society, 22, 1–19.
Graber, T., Bzoch, K., & Aoba, T. (1959). A functional study of the palatal and pharyngeal structures. Angle Orthodontist, 29, 30–40.
Hairfield, W., Warren, D., Hinton, V., & Seaton, D. (1987). Inspiratory and expiratory effects of nasal breathing. Cleft Palate Journal, 24, 183–189.
Harrington, R. (1944). A study of the mechanism of velopha- ryngeal closure. Journal of Speech Disorders, 9, 325–345.
Hixon, T., & Abbs, J. (1980). Normal speech production. In T. Hixon, L. Shriberg, & J. Saxman (Eds.), Introduction to communication disorders (pp. 42–87). Englewood Cliffs, NJ: Prentice-Hall.
Hiyama, S., Ono, T., Ishiwata, Y., & Kuroda, T. (2002). Effects of mandibular position and body posture on nasal patency in normal awake subjects. Angle Orthodontist, 72, 547–553.
Hoit, J., Watson, P., Hixon, K., McMahon, P., & Johnson, C. (1994). Age and velopharyngeal function during speech production. Journal of Speech and Hearing Research, 37, 295–302.
Honjo, I., Harada, H., & Kumazasa. T. (1976). Role of the leva- tor veli palatini muscle in movement of the lateral pharyn- geal wall. Archives of Otology, Rhinology, and Laryngology, 212, 93–98.
House, A., & Stevens, K. (1956). Analog studies of the nasal- ization of vowels. Journal of Speech and Hearing Disorders, 21, 218–232.
Hsu, H., Fogel, A., & Cooper, R. (2000). Infant vocal develop- ment during the first 6 months: Speech quality and melodic complexity. Infant and Child Development, 9, 1–16.
Huang, Z., Lee, S., & Rajendran, K. (1997). Structure of the musculus uvulae: Functional and surgical implications of an anatomic study. Cleft Palate-Craniofacial Journal, 34, 466–474.
Hutchinson, J., Robinson, K., & Nerbonne, M. (1978). Patterns of nasalance in a sample of normal gerontologic subjects. Journal of Communication Disorders, 11, 469–481.
Iglesias, A., Kuehn, D., & Morris, H. (1980). Simultaneous assessment of pharyngeal wall and velar displacement for selected speech sounds. Journal of Speech and Hearing Research, 23, 429–446.
Isshiki, N., Harita, Y., & Kawano, M. (1985). What muscle is responsible for lateral pharyngeal wall movement? Annals of Plastic Surgery, 14, 224–227.
Jackson, R. (1976). Nasal-cardiopulmonary reflexes: A role of the larynx. Annals of Otology, Rhinology, and Laryngology, 85, 65–70.
EBSCOhost - printed on 10/23/2020 8:35 PM via CUNY LEHMAN COLLEGE. All use subject to https://www.ebsco.com/terms-of-use
Foundations of Speech and Hearing: Anatomy and Physiology154
Jaw, T., Sheu, R., Liu, G., & Lin, W. (1999). Development of adenoids: A study by measurement with MR images. Kaoh- siung Journal of Medical Sciences, 15, 12–18.
Kaltenborn, A. (1948). An x-ray study of velopharyngeal closure in nasal and non-nasal speakers (Master’s thesis). Northwest- ern University, Evanston, IL.
Karlsson, S., & Carlsson, G. (1990). Characteristics of man- dibular movement in young and elderly dentate subjects. Journal of Dental Research, 69, 473–476.
Kent, R., Carney, P., & Severeid, L. (1974). Velar movement and timing: Evaluation of a model for binary control. Jour- nal of Speech and Hearing Research, 17, 470–488.
Kent, R., & Murray, A. (1982). Acoustic features of infant vocalic utterances at 3, 6, and 9 months. Journal of the Acous- tical Society of America, 72, 353–365.
Kuehn, D. (1976). A cineradiographic investigation of velar movement variables in two normals. Cleft Palate Journal, 13, 88–103.
Kuehn, D. (1990). Commentary on Doyle, Casselbrandt, Swarts, and Bluestone (1990): Observations on a role for the tensor veli palatini in intrinsic palatal function. Cleft Palate Journal, 27, 318–319.
Kuehn, D., & Azzam, N. (1978). Anatomical characteristics of palatoglossus and the anterior faucial pillar. Cleft Palate Journal, 15, 349–359.
Kuehn, D., Folkins, J., & Cutting, C. (1982). Relationships between muscle activity and velar position. Cleft Palate Journal, 19, 25–35.
Kuehn, D., & Kahane, J. (1990). Histologic study of the nor- mal human adult soft palate. Cleft Palate Journal, 27, 26–34.
Kuehn, D., & Moon, J. (1998). Velopharyngeal closure force and levator veli palatini activation levels in varying pho- netic contexts. Journal of Speech, Language, and Hearing Research, 41, 51–62.
Kuehn, D., & Moon, J. (2005). Histologic study of intravelar structures in normal human adult specimens. Cleft Palate- Craniofacial Journal, 42, 481–489.
Kuehn, D., & Perry, J. (2008). Anatomy and physiology of the velopharynx. In J. Losee & R. Kirschner (Eds.), Comprehen- sive cleft care. New York, NY: McGraw-Hill Medical.
Leeper, H., Tissington, M., & Munhall, K. (1998). Temporal aspects of velopharyngeal function in children. Cleft Palate- Craniofacial Journal, 35, 215–221.
Lester, R., & Hoit, J. (2014). Nasal and oral inspiration during natural speech breathing. Journal of Speech, Language, and Hearing Research, 57, 734–742.
Liss, J., Kuehn, D., & Hinkle, K. (1994). Direct training of velo- pharyngeal musculature. Journal of Medical Speech Language Pathology, 2, 243–249.
Lubker, J. (1968). An electromyographic-cinefluorographic investigation of velar function during normal speech pro- duction. Cleft Palate Journal, 5, 1–18.
McClean, M. (1973). Forward coarticulation of velar move- ment at marked junctural boundaries. Journal of Speech and Hearing Research, 16, 286–296.
McKerns, D., & Bzoch, K. (1970). Variations in velopharyngeal valving: The factor of sex. Cleft Palate Journal, 7, 652–662.
McWilliams, B., Morris, H., & Shelton, R. (1990). Cleft palate speech (2nd ed.). Philadelphia, PA: B. C. Decker.
Miller, M., Martin, R., Waldemar, A., Fouke, J., Strohl, K., & Fanaroff, M. (1985). Oral breathing in newborn infants. Journal of Pediatrics, 107, 465–469.
Moll, K. (1962). Velopharyngeal closure on vowels. Journal of Speech and Hearing Research, 5, 30–37.
Moll, K., & Daniloff, R. (1971). Investigation of the timing of velar movements during speech. Journal of Speech and Hear- ing Research, 50, 678–684.
Moon, J., & Canady, J. (1995). Effects of gravity on velopha- ryngeal muscle activity during speech. Cleft Palate-Cranio- facial Journal, 32, 371–375.
Moon, J., & Kuehn, D. (2004). Anatomy and physiology of normal and disordered velopharyngeal function for speech. In K. R. Bzoch (Ed.), Communicative disorders relat- ed to cleft lip and palate (5th ed., pp. 67–98). Austin, TX: Pro-Ed.
Moon, J., Kuehn, D., & Huisman, J. (1994a). Measurement of velopharyngeal closure force during vowel production. Cleft Palate-Craniofacial Journal, 31, 356–363.
Moon, J., Smith, A., Folkins, J., Lemke, J., & Gartlan, M. (1994b). Coordination of velopharyngeal muscle activity during positioning of the soft palate. Cleft Palate-Craniofacial Journal, 31, 45–55.
Morris, H. (1975). The speech pathologist looks at the tonsils and the adenoids. Annals of Otology, Rhinology, and Laryn- gology, 84, 63–66.
Netsell, R. (1990). Commentary. Cleft Palate Journal, 27, 58–60. Nusbaum, E., Foly, L., & Wells, C. (1935). Experimental studies
of the firmness of the velar-pharyngeal occlusion during the production of the English vowels. Speech Monographs, 2, 71–80.
Oller, K. (1986). Metaphonology and infant vocalizations. In B. Lindblom & R. Zetterstrom (Eds.), Precursors of early speech (pp. 21–36). New York, NY: Stockton Press.
Poppelreuter, S., Engelke, W., & Bruns, T. (2000). Quantitative analysis of the velopharyngeal sphincter function during speech. Cleft Palate-Craniofacial Journal, 37, 157–165.
Rodenstein, D., Perlmutter, N., & Stanescu, D. (1985). Infants are not obligatory nasal breathers. American Review of Respi- ratory Disease, 131, 343–347.
Rudcrantz, H. (1969). Postural variations of nasal patency. Acta Otolaryngologica, 68, 435–443.
Ruscello, D. (1982). A selected review of palatal training pro- cedures. Cleft Palate Journal, 19, 181–193.
Sasaki, C., Levine, P., Laitman, J., & Crelin, E. (1977). Postna- tal descent of the epiglottis in man. Archives of Otolaryngol- ogy, 103, 169–171.
Seaver, E., Dalston, R., Leeper, H., & Adams, L. (1991). A study of nasometric values for normal nasal resonance. Journal of Speech and Hearing Research, 34, 715–721.
Seaver, E., & Kuehn, D. (1980). A cineradiographic and elec- tromyographic investigation of velar positioning in non- nasal speech. Cleft Palate Journal, 17, 216–226.
Shelton, R., Beaumont, K., Trier, W., & Furr, M. (1978). Video- panendoscopic feedback in training velopharyngeal clo- sure. Cleft Palate Journal, 15, 6–12.
Shimokawa, T., Yi, S., & Tanaka, S. (2005). Nerve supply to the soft palate muscles with special reference to the distribu- tion of the lesser palatine nerves. Cleft Palate-Craniofacial Journal, 42, 495–500.
EBSCOhost - printed on 10/23/2020 8:35 PM via CUNY LEHMAN COLLEGE. All use subject to https://www.ebsco.com/terms-of-use
4 Velopharyngeal-Nasal Function and Speech Production 155
Shprintzen, R. (1992). Assessment of velopharyngeal func- tion: Nasopharyngoscopy and multiview videofluoros- copy. In L. Brodsky, L. Holt, & D. Ritter-Schmidt (Eds.), Craniofacial anomalies: An interdisciplinary approach (pp. 196– 207). St. Louis, MO: Mosby.
Shprintzen, R., McCall, G., Skolnick, L., & Lenicone, R. (1975). Selective movement of the lateral aspects of the pharyngeal walls during velopharyngeal closure for speech, blowing, and whistling in normals. Cleft Palate Journal, 12, 51–58.
Siegel-Sadewitz, V., & Shprintzen, R. (1986). Changes in velo- pharyngeal valving with age. International Journal of Pediat- ric Otorhinolaryngology, 11, 171–182.
Skolnick, M. (1970). Videofluoroscopic examination of the velopharyngeal portal during phonation in lateral and basal projections—A new technique for studying the mechanics of closure. Cleft Palate Journal, 7, 803–816.
Skolnick, M., McCall, G., & Barnes, M. (1973). The sphincteric mechanism of velopharyngeal closure. Cleft Palate Journal, 10, 286–305.
Stoksted, P. (1953). Rhinometric measurements for determi- nation of the nasal cycle. Acta Otolaryngologica, Supplement 109, 1–159.
Subtelny, J., & Koepp-Baker, H. (1956). The significance of adenoid tissue in velopharyngeal function. Plastic and Reconstructive Surgery, 12, 235–250.
Thom, S., Hoit, J., Hixon, T., & Smith, A. (2006). Velopharyn- geal function during vocalization in infants. Cleft Palate- Craniofacial Journal, 43, 539–546.
Thompson, A., & Hixon, T. (1979). Nasal air flow during nor- mal speech production. Cleft Palate Journal, 16, 412–420.
Tomoda, T., Morii, S., Yamashita, T., & Kumazawa, T. (1984). Histology of human eustachian tube muscles: Effect of aging. Annals of Otology, Rhinology, and Laryngology, 93, 17–24.
Tucker, L. (1963). Articulatory variations in normal speakers with changes in vocal pitch and effort (Master’s thesis). University of Iowa, Iowa City.
Vorperian, H., Kent, R., Lindstrom, M., Kalina, C., Gentry, L., & Yandell, B. (2005). Development of vocal tract length during childhood: A magnetic resonance imaging study. Journal of the Acoustical Society of America, 117, 338–350.
Warren, D., Dalston, R., & Dalston, E. (1990). Maintaining speech pressures in the presence of velopharyngeal impair- ment. Cleft Palate Journal, 27, 53–58.
Warren, D., Dalston, R., Trier, W., & Holder, M. (1985). A pressure-flow technique for quantifying temporal pat- terns of palatopharyngeal closure. Cleft Palate Journal, 22, 11–19.
Warren, D., & DuBois, A. (1964). A pressure-flow technique for measuring velopharyngeal orifice area during continu- ous speech. Cleft Palate Journal, 1, 52–71.
Warren, D., Hairfield, W., Seaton, D., Morr, K., & Smith, L. (1988). The relationship between nasal airway size and nasal-oral breathing. American Journal of Orthodontics and Dentofacial Orthopedics, 93, 289–293.
Warren, D., Mayo, R., Zajac, D., & Rochet, A. (1996). Dyspnea following experimentally induced increased nasal airway resistance. Cleft Palate-Craniofacial Journal, 33, 231–235.
Wasz-Hockert, O., Lind, J., Vuorenkoski, V., Partanen, T., & Valanne, E. (1964). The infant cry: A spectrographic and auditory analysis. Clinics in Developmental Medicine, Sup- plement 29. London, UK: Heinemann.
Zaino, C., & Benventano, T. (1977). Functional, involutionale- ment, and degenerative disorders. In C. Zaino & T. Ben- ventano (Eds.), Radiologic examination of the oropharynx and esophagus (pp. 141–170). New York, NY: Springer-Verlag.
Zajac, D. (1997). Velopharyngeal function in young and older adult speakers: Evidence from aerodynamic studies. Jour- nal of the Acoustical Society of America, 102, 1846–1852.
Zajac, D. (2000). Pressure-flow characteristics of /m/ and /p/ production in speakers without cleft palate: Developmen- tal findings. Cleft Palate-Craniofacial Journal, 37, 468–477.
Zajac, D., & Hackett, A. (2002). Temporal characteristics of aerodynamic segments in the speech of children and adults. Cleft Palate-Craniofacial Journal, 39, 432–438.
Zajac, D., & Mayo, R. (1996). Aerodynamic and temporal aspects of velopharyngeal function in normal speakers. Journal of Speech and Hearing Research, 39, 1199–1207.
Zankl, A., Eberle, L., Molinari, L., & Schinzel, A. (2002). Growth charts for nose length, nasal protrusion, and phil- trum length from birth to 97 years. American Journal of Med- ical Genetics, 111, 388–391.
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