Resonation and Articulation: Structures and Processes

Resonation and Articulation: Structures and Processes

1. Fundamentals of Resonation

   • Vocal folds vibrate to produce voice. Resonation is process were voice, or laryngeal tone, is modified  when some frequency components  are dampened and others are enhanced. Resonators that serve to modify laryngeal tone are pharynx, nasal cavity, and oral cavity. 
   • Pharynx
     • Pharynx, or throat, is part of upper airway. Located superiorly and posteriorly to larynx. Size and shape of pharynx are modified by the position of tongue in the mouth  (forward or back) and the vertical positioning of the larynx in the neck (high or low).
     • Nasal Cavity
       • Important in resonation. Only three sounds in English-/m/, /n/, and /ng/-are produced with nasal resonance. During production of these sounds, soft palate (velum), is relaxed and lowered. Thus, there is coupling of nasal and oral cavities, they are not separated from none another. 
       • Velum
         • Elevated and retracted for production of all other sounds in English. During production of those sounds, velum is raised and retracted, to make contact with the posterior pharyngeal wall, separating oral cavity from nasal cavity. Cavities are thus uncoupled.  In this way, sounds are produced mainly with oral resonance. 
         • Oral Cavity
           • Primary resonating structure for all English sounds except-/m/, /n/, and /ng/. Source-Filter Theory of vowel production also called acoustic theory of vowel production- provides widely accepted description of how oral cavity is capable of producing speech sounds. 
           • Source-Filter Theory
             • Vocal tract is visualized as series of linked tubes: oral cavity, pharynx, and nasal cavity. These linked tubes provide variable resonating cavity that helps produce speech. The theory states that energy from vibrating vocal folds (the source) is modified by resonance characteristics of vocal tract (the filter). 
             • Vocal folds generate a voicing source. Voicing source is routed through vocal tract, where it's shaped into speech sounds. Speech sounds may be vowels when when source is phonation, and consonants when sources include the turbulence of frication or combinations of turbulence and voicing. 
             • Changes in configuration and shape of articulators govern resonance characteristics of vocal tract. Resonance of vocal tract determine sound of each specific vowel. Whether consonants or vowels are produced, in each case the person produces a noise source and passes it through the filter of the oral cavity, which has been specifically configured for production of that sound
             • Structures within the oral cavity are shaped and moved to provide specific resonance for each sound. These structures are key in the process of articulation. 

2. Fundamentals of Articulation

   • Articulation refers to the connection of movable parts or the  joining of two elements. In speech, articulation is the movement of speech structures to produce speech sounds. Also refers to the act of saying something clearly. For SLP's it mainly means movement of joined anatomical parts as well as the production of speech sounds that result from such movements. 
   • Larynx produces sound that is shaped into speech. Sound travels through pharynx and oral cavity (and nasal cavity for nasal sounds). In the oral cavity, important structures modify the sound into specific sounds for speech. These structures include pharynx, soft palate, hard palate, mandible, teeth, tongue, lips and cheeks.
   • Pharynx
     • Divided into three segments: 1. Laryngopharynx: immediately begins superior to larynx and ends at base of the tongue.Connected to oropharynx 2. Oropharynx: extends up to soft palate and is connected to nasopharynx.  3. Nasopharynx: ends where two nasal cavities begin.
     • Laryngopharynx and oropharynx add resonance to sounds produced by the larynx. However, nasopharynx adds noticeable resonance only to the nasals, /m/, /n/, and /ng/.
     • Muscles of Pharynx
       • 1. Salpingopharyngeus (X, XI): Elevates lateral pharyngeal wall. 2. Stylopharyngeus (IX): Elevates and opens pharynx. 3. Superior pharyngeal constrictor (X, XI): Constricts pharyngeal diameter, pulls pharyngeal wall forward.  4. Middle pharyngeal constrictor (X, XI): Narrows diameter of pharynx. 5. Inferior pharyngeal constrictor, cricopharyngeus (X.XI): Constricts superior oriface of esophagus.  6. Inferior pharyngeal constrictor, thyropharyngeus (X, XI): Reduces diameter of lower pharynx.
       • Soft Palate
         • The velum (soft palate) is a flexible muscular structure at the juncture of the nasopharynx and oropharynx. Located in the posterior area of the oral cavity and hangs from the hard palate (roof of mouth). Uvula is the small, cone-shaped structure at the tip of the velum. 
         • Soft palate is a dynamic structure of muscles That can be elevated or lowered. When velum is lowered, there is coupling of the nasal and oral cavities for nasal sounds or quiet breathing through the nose. 
         • When vellum is raised and retracted, muscles of the pharynx also move inward to meet the muscles of the soft palate. With sphincter-like action, the nasal port is then closed. This is called velopharyngeal closure. 
         • If muscular bulk of soft palate is inadequate, nasal cavity may remain open to some extent. Speakers with this condition sound excessively nasal because sound energy passes through the nasal cavities when it should not. 
         • Muscles of Soft Palate
           • These are the muscles of the soft palate, their innervations, and their functions: 1. Levator Veli Palatini (X, XI): primary elevator of velum 2. Tensor Veli Palatini (V): tenses velum, dilutes eustachian tube. 3. palatoglossus (X, XI): elevates and depresses velum. 4. Palatopharyngeus (X, XI): narrows pharyngeal cavity, lowers velum, may assist in elevating larynx.
           • Hard Palate
             • Bony hard palate is roof of mouth and floor of nose. It's part of maxillae, or paired bones, which are largest in face and form untire upper jaw. Maxillae also called maxillary bone. 
             • Front portion of maxillary bone is called pre maxilla. It houses the four upper front teeth known as the incisors.  Portion of maxillary bone that forms most of hard palate is called palatine process. Consists of two pieces of bone that grow and fuse at midline during the fetal stage. Outer edges of maxillary bone are called the alveolar process, which houses the molar, bicuspid, and cuspid teeth. 
             • For genetic and toxic environmental reasons, the pre maxilla may fail to fuse with maxillary bone. Also, palatine process may fail to fuse at midline. These failures cause cleft palate in utero. 
             • Posteriorly, the maxillary bone joins with the palatine bone (different from palatine process, which is part of maxillary bone). Soft palate attaches to palatine bone. 
             • Mandible
               • Important facial bone. Also known as lower jaw. Houses lower teeth and forms floor of mouth. Formed by fusion of two bones in midpoint of the chin, but is considered one bone in adults.
               • Alveolar arch is part of mandible that houses the teeth. Two arches of mandible are hinged to the skull with a set of muscles and tendons. Mandible is attached to temporal bone of skull by the temporomandibular joint. 
               • Muscles of mandible serve two major functions: (a) opening and closing the mouth (b) chewing food Although its major flask is chewing food, mandible is important for speech because it houses lower teeth, serves as framework for tongue and lower lip, and is integral part of oral cavity. 
               • Elevators of Mandible
                 • These are the elevators of the mandible, their innervations, and their functions: 1. Masseter (V): Elevates mandible. 2. Temporalis (V): Elevates mandible, draws mandible back if protruded. 3. Medial (internal) pterygoid (V): Elevates mandible. 4. Lateral (external) pterygoid (V): Protrudes mandible.
               • Depressors of Mandible
                 •  These are the depressors of the mandible, their innervations, and their functions: 1. Anterior belly of digastric (V): depresses mandible in conjunction with posterior belly of digastric; pulls hyoid forward. 2. Posterior belly of digastric (VII): depresses mandible in conjunction with anterior belly of digastric; pulls hyoid back. 3. Geniohyoid (XII, CI): depresses mandible. 4. Mylohyoid (V): Depresses mandible
               • Teeth
                 • Lower dental arch is part of mandible, and upper dental arch is part of maxillary bone. Major function of teeth is mastication (chewing), but teeth also aid in production of some speech sounds. For example, labiodental sounds /f/ and /v/ require lower lip to come in contact with upper feet. Thus, teeth are considered articulators.
                 • Teeth are called different names depending on location in the mouth. Deciduous teeth are temporary teeth that appear in  baby , usually around 6 to 9 months. Babies normally have 20 deciduous teeth, 10 per arch. Of the 10, 4 are incisors, 2 are canine, and 4 are molar. 
                 • Adults have 32 teeth, 16 per arch. Of 16 test, 4 are incisors, 2 are canine, 4 are premolar, and 6 are molar. Deciduous dental arch doesn't have premolars or third molars.
                 • Occlusion
                   • The way two dental arches come together when a person "bites down." Occlussion is normal if  (a) Upper and lower dental arches meet each other in a symmetrical manner, and (b) If the individual teeth in both arches are properly aligned. 
                 • Maloclussions
                   • Maloclussions include deviations in the positioning of individual teeth and the shape and relationship of the upper and lower dental arches.
                 • Tongue
                   • Plays an important role in eating and speech production. Taste buds of the tongue help people taste food, and muscles of tongue help it to move food around the oral cavity for efficient mastication and swallowing. Movements of tongue are critical to articulation. For example, tongue movement is necessary to produce /k/, /ng/, and many other sounds. Tongue can also constrict air passage and thus create friction needed for sounds such as /$/.
                   • Tongue is divided into four major parts: 1 Tip: Thinnest and most flexible part of tongue; plays important role in articulation. 2. Blade: Small region adjacent to tip; in a resting position, blade is portion of tongue that lies just inferior to alveolar ridge. 3. Dorsum: Large are of tongue that lies in contact with both hard and soft palates. 4. Root: Very back and bottom portion of tongue.
                   • Lingual frenulum connects mandible with inferior portion of tongue. This band of tissue may stabilize the tongue during movement.
                   • Extrinsic Muscles
                     • All muscles of tongue innervated by cranial nerve XII: 1. Genioglossus: Forms bulk of tongue; is able to retract tongue, draw tongue downward, draw entire tongue anteriorly to protrude tip or press tip against alveolar ridges and teeth.. 2. Styloglossus: Draws tongue up and back, may draw sides of tongue upward to help make dorsum concave. 3. Hyoglossus: Retracts and depresses tongue. 4. Chondroglossus: Depresses tongue. 5. Palatoglossus: Some consider it a muscle of the velum, but it helps elevate the tongue (but depresses the velum).
                   • Intrinsic Muscles of Tongue
                     • All muscles of tongue innervated by cranial nerve (XII): 1. Superior Longitudinal Muscle: Shortens tongue, turns tip upward, assists in turning lateral margins upward. 2. Inferior Longitudinal Muscle: Shortens tongue, pulls tip downward, assists in retraction. 3. Transverse Muscles: Narrow and elongate tongue. 4. Vertical Muscles: Flattens tongue
                   • Face: Lips and Cheeks
                     • Muscles of face assist in producing various sounds, especially labial sounds /m/, /b/, and /p/.
                     • Primary muscle of lips is obicularis oris. Cheeks are primarily composed buccinator muscle, a large flat muscle whose inner surface is covered with mucous membrane.
                     • Muscles of Face
                       • All innervated by buccal branches or mandibular marginal branch of cranial nerve VII (Facial Nerve). Following are the muscles, innervations, and functions of facial muscles.
                       • 1. Mentalis: Pulls lower lip out, wrinkles and elevates chin. 2. Platysma: Depresses mandible. 3. Risorius: Retracts lips at corners. 4. Buccinator: Constricts oropharynx; moves food onto grinding surfaces of molars. 5. Depressor Labii Inferioris: Pulls lips down and out to dilate orifice. 6. Depressor anguli oris (Triangularis): Helps to press lower and upper lips together; depresses corners of mouth.
                       • 7. Zygomatic minor: Elevates upper lip. 8. Zygomatic major: Retracts and elevates angle of mouth. 9. Obicularis oris inferioris and superioris: Pulls lips together, seals lips, serves as point of insertion for other muscles, interacts with other muscles to produce facial expressions. 10. Levator anguli oris: Draws corners of mouth upward and toward medial. 11. Levator labii superioris: Elevates upper lip. 12. Levator labii superioris alaque nasi: Elevates upper lip.

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