Anatomy and Physiology of the speech mechanism

Anatomy

The study of body structures and where they are located.

Physiology

The study of how body structures function and work.

Speech science

The study of the physical and biological processes involved in speech production.

Respiratory subsystem

Provides the airflow and energy needed for speech.

Phonatory subsystem

Produces the sound source through vibration of the vocal folds.

Resonatory subsystem

Modifies and shapes the sound produced by the vocal folds.

Articulatory subsystem

Shapes sound into recognizable speech sounds using structures such as the tongue, lips, teeth, jaw, and palate.

Four speech subsystems

Respiration, phonation, resonance, and articulation.

Respiration

Airflow/energy for speech.

Phonation

Sound production through vocal fold vibration.

Resonance

Modification and shaping of sound.

Articulation

Shaping sound into speech sounds.

Sagittal plane

Divides the body into left and right portions.

Coronal/frontal plane

Divides the body into anterior/front and posterior/back portions.

Transverse/horizontal plane

Divides the body into superior/upper and inferior/lower portions.

Anterior

Toward the front of the body.

Posterior

Toward the back of the body.

Superior

Above or toward the head.

Inferior

Below or toward the feet.

Medial

Toward the body's midline.

Lateral

Away from the body's midline.

Proximal

Closer to the point of attachment.

Distal

Farther from the point of attachment.

Epithelial tissue

Covers surfaces and lines organs and body cavities; provides protection and can absorb or secrete substances.

Connective tissue

Supports, connects, protects, and provides structural framework for the body.

Ligament

Connects bone to bone and helps stabilize joints.

Tendon

Connects muscle to bone and transfers muscular force to create movement.

Synarthrosis

A joint that is immovable or nearly immovable; highly stable.

Amphiarthrosis

A slightly movable joint with limited movement and moderate stability.

Diarthrosis

A freely movable joint; generally allows greater movement but can be less stable.

Joint mobility vs stability

Generally, as mobility increases, stability decreases; as mobility decreases, stability increases.

Excitability

A muscle's ability to respond to stimulation.

Contractility

A muscle's ability to shorten and generate force.

Extensibility

A muscle's ability to stretch.

Elasticity

A muscle's ability to return toward its original length after being stretched.

Diaphragm

The primary muscle of inspiration; a dome-shaped muscle separating the thoracic and abdominal cavities.

Visceral pleura

The pleural membrane attached to the surface of the lungs.

Parietal pleura

The pleural membrane lining the inside of the thoracic cavity.

Pleural space

The thin fluid-filled space between the visceral and parietal pleura.

Pleural pressure

Normally negative relative to atmospheric pressure; helps keep the lungs expanded.

Lung-thorax unit

The lungs and thorax working together as a mechanically linked respiratory system.

Pleural linkage

The mechanical connection between the lungs and thoracic wall through the pleural membranes and fluid.

Negative pleural pressure

Pressure in the pleural space that is normally below atmospheric pressure.

Boyle's Law

At constant temperature, pressure and volume are inversely related.

Boyle's Law: volume

When volume increases, pressure decreases.

Boyle's Law: pressure

When volume decreases, pressure increases.

Inspiration

Air enters the lungs because lung volume increases and lung pressure decreases.

Expiration

Air leaves the lungs because lung volume decreases and lung pressure increases.

Quiet inspiration

An active process involving contraction of the diaphragm and usually the external intercostals.

Quiet expiration

A mostly passive process caused by muscle relaxation and elastic recoil.

Forced expiration

An active process that can involve the internal intercostals and abdominal muscles.

Primary muscle of inspiration

The diaphragm.

Primary muscles assisting inspiration

The external intercostals and, when needed, accessory inspiratory muscles.

Primary muscles of forced expiration

The internal intercostals and abdominal muscles.

Thoracic volume during inspiration

Increases.

Thoracic volume during expiration

Decreases.

Lung volume during inspiration

Increases.

Lung volume during expiration

Decreases.

Lung pressure during inspiration

Becomes negative relative to atmospheric pressure, allowing air to enter.

Lung pressure during expiration

Becomes positive relative to atmospheric pressure, allowing air to leave.

Tidal volume (TV)

The amount of air moved during a normal, quiet breath.

Inspiratory reserve volume (IRV)

The additional amount of air that can be inhaled after a normal inspiration.

Expiratory reserve volume (ERV)

The additional amount of air that can be exhaled after a normal expiration.

Residual volume (RV)

The amount of air remaining in the lungs after a maximal expiration.

Inspiratory capacity (IC)

The maximum amount of air that can be inhaled starting from the end of a normal expiration.

IC formula

IC = IRV + TV.

Functional residual capacity (FRC)

The amount of air remaining in the lungs after a normal, quiet expiration.

FRC formula

FRC = ERV + RV.

Vital capacity (VC)

The maximum amount of air that can be voluntarily moved in and out of the lungs.

VC formula

VC = IRV + TV + ERV.

Total lung capacity (TLC)

The total amount of air in the lungs after a maximal inspiration.

TLC formula

TLC = IRV + TV + ERV + RV.

Resting expiratory level (REL)

The lung volume at the end of a normal, quiet expiration.

REL and FRC

REL is approximately associated with FRC because both refer to the lung volume remaining after a normal quiet expiration.

Active force

A force produced by muscle contraction.

Passive force

A force produced by relaxation, elastic recoil, or other restoring forces without active muscle contraction.

Elastic recoil

The tendency of stretched tissue, such as the lungs, to return toward its original shape or size.

Relaxation-pressure curve

A representation of the relationship between lung volume and the passive pressure generated by the respiratory system.

High lung volume

The lungs have a stronger tendency to recoil inward, creating a greater passive expiratory force.

Low lung volume

The chest wall tends to have a stronger outward recoil tendency.

Checking action

Muscular activity used to control or oppose passive respiratory forces.

Inspiratory checking action

At high lung volumes, inspiratory muscle activity can oppose/control strong passive expiratory recoil.

Expiratory checking action

At low lung volumes, expiratory muscle activity can oppose/control the tendency toward inspiration.

Psg

Subglottal pressure used for speech.

Pr

Passive recoil pressure.

Pmc

Muscular pressure/checking action.

Speech pressure equation

Psg = Pr + Pmc.

Why checking action matters for speech

It allows the speaker to control respiratory pressure and airflow instead of simply allowing passive recoil to determine airflow.

Starting speech at low lung volumes

Not efficient or advantageous because there is less available air and maintaining adequate pressure can require greater muscular effort.

Net force

The combined/resulting effect of all forces acting on a system.

Why use the term net force

Because multiple forces can act simultaneously and may assist or oppose one another.

Airflow direction when lung pressure is lower than atmospheric pressure

Air flows into the lungs.

Airflow direction when lung pressure is higher than atmospheric pressure

Air flows out of the lungs.

No airflow condition

There is no pressure difference between the lungs and atmosphere.

Inspiration sequence

Diaphragm contracts → thoracic volume increases → lung volume increases → lung pressure decreases → air enters.

Expiration sequence

Diaphragm relaxes → thoracic/lung volume decreases → lung pressure increases → air exits.

High-volume checking rule

High lung volume → strong passive expiratory recoil → inspiratory checking action.

Low-volume checking rule

Low lung volume → outward chest-wall tendency → expiratory checking action.

Most important Boyle's Law rule

Volume up = pressure down; volume down = pressure up.

Most important speech subsystem order

Respiration → Phonation → Resonance → Articulation.