Speech Anatomy and Physiology Notes
Introduction: Overview of physiology and speech anatomy
Physiology: study of the functions of the body and its parts; Greek origins: physis = nature, logia = to speak; thus physiology involves describing the nature of things.
Anatomy vs physiology: gross (structure visible to the naked eye) and cellular (histology) focus; foundational courses for medical, audiology, and speech-language pathology students.
Purpose for speech sciences: understanding normal communication and disorders; material is revisited in later chapters addressing anatomical/physiological abnormalities.
Speech anatomy integrates three subsystems used for speech production: (a) respiratory, (b) laryngeal, (c) articulatory; these structures were originally for basic survival (breathing, swallowing, coughing) and are now exploited for communication.
Speech Anatomy: three subsystems
Respiratory system: provides the airstream source for speech.
Laryngeal system: modulates voice source and phonation.
Articulatory system: shapes the vocal tract to produce distinct speech sounds.
All three systems work together to produce speech; the same anatomy serves non-speech functions like breathing, swallowing, and coughing.
Respiratory System: components and organization
Major components: lungs, diaphragm, rib cage, trachea, pharynx, and oral/nasal passages.
Respiratory tracts:
Upper respiratory tract: oral and nasal cavities and pharynx.
Lower respiratory tract: trachea, bronchi, and lungs.
Air entry and conditioning:
Air inhaled mainly through the nostrils into the nasal cavity.
Nasal cavity lined with mucous membranes and cilia to warm, moisten, and filter air.
Mouth breathing considerations:
Breathing through the mouth bypasses nasal conditioning, leading to less filtered/warmed air.
Increased risk of irritation, inflammation, and upper respiratory infections; may be a sign of nasal obstruction (e.g., enlarged adenoids) requiring mouth breathing.
Adenoids and tonsils:
Adenoids are paired lymphoid tissues at the back of the nasal cavity that filter inhaled debris.
Respiratory Tract Anatomy: Figure reference and functional details
Figure 2–1 location overview for respiratory structures.
Pharynx: a hollow tube (~5 in / 12.7 cm) behind the nose continuing to the trachea and esophagus; serves dual roles for swallowing and respiration.
Pharyngeal and airway branching:
The pharynx splits into the trachea (laryngeal airway) and the esophagus (food tube).
Food directed toward the esophagus during swallowing; air directed toward the trachea and lungs during respiration.
Breathing rate across lifespan:
At rest: about 14–16 breaths per minute.
After exercise: >60 breaths per minute.
Newborns at rest: 40–50 breaths per minute.
By age 5: ~25 breaths per minute.
Trachea, Bronchi, Bronchioles, and Alveoli: Gas exchange and airway structure
Trachea: main airway carrying air to/from the lungs; elastic tissue with about 20 rings of cartilage; designed for flexibility to accommodate head/neck movement while breathing.
Bronchi: primary divisions of the trachea; split into right and left main bronchi to each lung.
Bronchioles: successive narrowing branches that distribute air within the lungs.
Alveoli: tiny air sacs at the ends of bronchioles; surrounded by capillaries; site of gas exchange: oxygen delivery to blood and carbon dioxide removal.
Functional consequences:
Oxygen is essential for cellular metabolism; carbon dioxide is a waste product exhaled.
The lungs occupy most of the chest cavity; left lung is slightly smaller to accommodate the heart.
The rib cage (12 pairs of ribs) protects the lungs and heart.
Diaphragm:
Primary muscle of respiration; located at the base of the rib cage.
During inhalation, diaphragm contracts downward and rib cage expands;
Diaphragm impairment can severely affect breathing.
Oxygen and air composition:
Air is a mixture of gases: mainly oxygen, nitrogen, and carbon dioxide; oxygen ~20% of air; nitrogen and carbon dioxide as well.
Respiratory Cycle and Speech Breathing
Respiratory cycle components:
Inhalation: active process using respiratory muscles to expand the lungs.
Exhalation: passive recoil of lungs under quiet breathing; air is expelled.
Speech-specific modulation:
In speech, inhalation accounts for about 10% of the cycle; exhalation accounts for about 90% to sustain speaking across larger utterances.
To prolong exhalation for speech, we can (a) inhale more air than in quiet breathing, and (b) prolong expiratory airflow by creating vocal tract resistance.
Balloon analogy for vocal tract resistance (Figure 2–3):
Large balloon inhale = large lung air; exhale with no resistance leads to quick air release.
If resistance is added (pinching end of balloon), exhalation is prolonged—analogy for speech: vocal fold resistance (phonation) and oral cavity resistance (articulation).
Practical implication: respiratory muscles relax gradually to avoid a rapid, forceful air release during speech.
Laryngeal System: framework and major structures
Laryngeal framework components: cartilage, muscles, and bone.
Key structures within the larynx:
Thyroid cartilage: largest laryngeal cartilage; features the laryngeal prominence (Adam’s apple);
Epiglottis: leaf-shaped cartilage above the larynx; protects airway during swallowing by directing food to the esophagus; not central to speech.
Hyoid bone: horseshoe-shaped, high in the neck; anchor for tongue muscles above and laryngeal muscles below; floating bone (no direct bone-to-bone attachments).
Cricoid cartilage: ring-shaped, resting atop the trachea; forms the base of the larynx.
These components collectively form the laryngeal framework from top to bottom.
Figure reference: 2–4.
The Vocal Folds and Phonation
Vocal folds (vocal cords): thyroarytenoid muscle; paired structures on the right and left.
Attachment points:
Anterior (front) attachment inside the thyroid cartilage near the Adam’s apple.
Posterior attachment to the arytenoid cartilages on top of the cricoid cartilage.
Glottis: the space between the vocal folds when they are open.
Phonation process:
During speech, air from the lungs builds up pressure beneath the closed vocal folds; when pressure is sufficient, folds vibrate rapidly as air is expelled through the glottis.
A common analogy: blowing air through two blades of grass held between your fingers can produce a squeal similar to vocal fold vibration.
Fundamental frequency (F0): basic rate of vocal fold vibration; perceived as voice pitch.
F0 values: for young children; for women; for men.
Larger, bulkier vocal folds vibrate more slowly and yield a lower F0; shorter/thinner folds vibrate faster and yield a higher F0 (see Fig. 2–5).
Visual reference: Fig. 2–6 shows sequential steps of vocal fold vibration.
Articulatory System: the movement and contact of speech structures
Articulation: movement of one structure against another to produce speech sounds.
Major articulatory structures (vocal tract from larynx to lips): cavities, muscles, and bones involved in articulation.
Vocal tract definition: an extended space within the body used for vocalization; consists of three cavities:
Oral (mouth)
Nasal (nose)
Pharyngeal (throat)
Movable (active) articulators:
Lips, tongue, soft palate (velum), pharynx, and mandible (lower jaw).
Lips contribute to sounds like /p/, /f/, /m/; ventriloquism is an exception where lips are minimized for effect.
Fixed (inflexible) articulators:
Hard palate, alveolar ridge, and teeth.
Hard palate (bone) forms the roof of the mouth and supports sounds like /sh/ in "shoe".
Alveolar ridge behind the upper teeth hosts sounds like /t/, /d/, /z/ in "two" and "dice"; teeth contribute to /v/, /f/, /th/ in "vie" and "faith".
The tongue:
Considered the most important speech articulator; not a single muscle but a complex set of overlapping muscles.
Essential for all vowel sounds and many consonants (e.g., /s/, /l/, /th/ in "sloth").
The mandible:
Lower jaw; bilateral hinge; contributes to articulation and overall speech clarity; continuous movement during typical speech.
Pipe speech (jaw constrained by a pipe) demonstrates how jaw movement affects speech clarity when movement is restricted.
The soft palate (velum):
The velum closes off the oral and nasal cavities by velopharyngeal closure when producing most vowels and consonants (except /m/, /n/, /ŋ/ in words like "meaning").
If velum remains lowered during speech, nasalization of most sounds would occur.
The pharynx:
Not only a cavity but also an active movable structure helping pharyngeal constriction and assisting with velopharyngeal closure.
Process of Speech Production: brain, energy, and transmission
Brain involvement:
Speech production begins with the brain encoding a message; language centers generate the plan and issue neural commands to respiratory, laryngeal, and articulatory systems.
Detailed brain anatomy and nervous system context are discussed in Chapter 9.
Energy transformation in speech:
Speech involves transforming aerodynamic energy (air from the lungs) into acoustic energy (sound).
Conceptual model: S * T = P, where:
S = source (respiratory system provides the initial energy)
T = transfer function (laryngeal and articulatory shaping; a filter-like transformation)
P = product (acoustic speech signal)
Formula and interpretation:
The respiratory system supplies the energy; the laryngeal and articulatory systems shape and transform that energy to produce speech sounds; the resulting acoustic signal is perceived as words and sentences.
Auditory nerve (peripheral to central):
The auditory nerve is also known as the acoustic nerve, eighth cranial nerve, or vestibulocochlear nerve; essential for both hearing and balance.
Hearing Anatomy: audition and the auditory pathway
Audition (hearing) components:
Peripheral auditory system: outer ear through to the auditory nerve.
Central auditory system: brain pathways analyzing the auditory signal.
Flow of sound:
Sounds are captured by outer ear structures, transmitted through the middle ear, converted to neural signals by the inner ear, and carried by the auditory nerve to the brain for interpretation.
The lecture connects hearing anatomy to speech research and disorders, emphasizing the integration of speech production and perception.
Real-world relevance and implications
Health and clinical relevance:
Mouth breathing can contribute to higher rates of upper respiratory infections and may be linked to asthma exacerbations.
Obstructions (e.g., enlarged adenoids) can force mouth breathing, highlighting the need to assess nasal patency in speech-language pathology.
Lung cancer statistics emphasize epidemiological context for pulmonology and phonation considerations in speech pathology.
Practical implications in therapy and assessment:
Understanding the respiratory support for speech informs therapy targeting breath control, phrasing, and prosody.
Knowledge of velopharyngeal closure is critical for diagnosing and treating hypernasality or hyponasality.
The dynamic interplay of movable vs fixed articulators guides articulation therapy and coordination across speech sound production.
Foundational connections:
The material links to foundational anatomy and physiology concepts, reinforcing why anatomy and physiology are prerequisites for understanding speech-language pathology.
Foundational formulas and numerical references (summary)
Speech energy transformation:
Fundamental frequency differences by speaker type:
(young children)
(women)
(men)
Key respiratory cycle proportions for speech: inhalation ≈ 10%, exhalation ≈ 90% of the cycle during speaking.
Oxygen content of air and gas exchange context: air ~20% O2; oxygen uptake for cellular processes; CO2 expelled during exhalation.
Clinical numbers for reference:
Lung cancer is the second most common cancer in both men and women; in 2023, about people died from lung cancer in the U.S. — roughly men and women.
Anatomy and protection: the rib cage consists of 12 pairs of ribs protecting lungs and heart; the diaphragm is the primary breathing muscle.
Structural relationships: left lung slightly smaller than the right to accommodate the heart; thyroid cartilage with Adam’s apple; hyoid bone as a floating anchor for tongue and laryngeal muscles; cricoid cartilage forms the base of the larynx.
Notation of anatomical terms and figures:
Figure references: 2–1 (respiratory), 2–2 (inspiratory/expiratory proportions), 2–3 (balloon analogy), 2–4 (laryngeal features), 2–5 (F0 vs vocal fold size), 2–6 (vocal fold vibration), 2–7 (articulatory system), 2–8 (additional articulatory details).
Glossectomy definition: surgical removal of all or part of the tongue, typically to treat tongue cancer; most patients retain some speech ability after partial glossectomy.
Masseter muscle: one of the strongest muscles, capable of exerting about of force during chewing.
Connections to prior and real-world contexts
Foundational anatomy and physiology are prerequisites for understanding speech and hearing disorders.
The chapter reinforces how physical structures (airway, larynx, articulators) directly influence speech production and perception, and how pathology or developmental variation can alter communication.
The integration of brain control with respiratory, laryngeal, and articulatory systems highlights the interdisciplinary nature of speech-language pathology, neurology, and physiology.