The Phonatory System Is the Source of Voiced Sound

PHONATORY SYSTEM

•  the phonatory system is the source of voiced sound

•  phonation is the generation of voiced sound

•  phonation is accomplished with the larynx (voice box), which is attached to the top of the trachea, and is the outlet of the respiratory pump into the upper airway

The larynx

•  is the structure at the entrance to the trachea that functions as a valve biologically and as the source of voice for speech

•  it can close tightly, as when we lift a heavy object, to make the thorax rigid with compressed air – providing stability to the body during heavy muscular activity

•  it can accomplish the explosive movements of a cough, expelling mucus and irritants at great velocity into the airway

•  it can valve the air stream so as to produce finely controlled vibrations of two fleshy cushions called the vocal folds

Functions of the larynx borrowed for speech:

•  the ability to open in order to produce about half of the consonants, the half that are voiceless sounds (these sounds are made with busts and hisses of noise)

•  the ability to close (al the level of the vocal folds) just enough to vibrate when air pressure pushes against it – these vibrations produce voiced sounds, the tones that characterize vowels and semivowels particularly

•  it is our ability of controlling the rate and manner of vibration of the laryngeal valve, that accounts for our ability to control pitch, loudness, and to some extent, quality of speech

The laryngeal anatomy

•  supraglottal cavity or supraglottal space or laryngeal aditus

•  false or ventricular folds

•  ventricle / ventricular cavity or ventricular space

•  vocal folds or true vocal folds

•  subglottal cavity

•  glottis

Laryngeal cartilages

•  cricoid

•  thyroid

•  arytenoid

–  vocal process

–  muscular process

–  apex

•  epiglottis

–  important during swallowing

•  corniculate and cuniform

–  no known function during speech production

Laryngeal membranes

•  Inner Laryngeal Membranes

•  quadrangular membrane

–  covers the supraglottic space

–  its lowest edge “makes” the false/ventricular fold

•  conus elasticus

–  covers the subglottic space

–  its uppermost edge “makes” the vocal ligament

Vocal Folds

•  located bellow the false/ventricular folds and bellow the ventricular space/cavity

•  attach anteriorly to the thyroid cartilage

•  attach posteriorly to the vocal process of the arytenoid cartilage

•  the space between the edges of the right and left vocal folds is known as glottis or glottic space

•  histologically is “made-up” by 5 layers of tissue

–  epithelium (most superficial)

–  superficial layer of the lamina propria (gelatinous)

–  intermediate layer of the lamina propria (elastic fibers like rubber bands)

–  deep layer of the lamina propria (collagenous fiber like threads)

–  vocalis muscle

•  vocal ligament

–  upper most medial edge of the conus elastic membrane

–  histologically

•  intermediate layer of the lamina propria (elastic fibers like rubber bands)

•  deep layer of the lamina propria (collagenous fiber like threads)

Laryngeal Muscles

•  intrinsic (move the arytenoids and control tension/length/mass of vocal folds )

•  extrinsic (move the entire larynx)

Intrinsic Laryngeal Muscles

•  thyroarytenoid (tenses and relaxes)

–  external/lateral thyroarytenoid - thyromuscularis - shorten the folds/act as relaxor

–  internal/medial thyroarytenoid - thyrovocalis/vocalis - tenses the folds during isometric contraction

•  isotonic

•  isometric

•  cricothyroid (tenses)

•  posterior cricoarytenoid (the only abductor muscle - move folds away from midline)

•  lateral cricoarytenoid (one of the adductor muscles - move the folds towards the midline)

•  interarytenoids (the other adductor muscles - move folds towards the midline)

–  oblique arytenoids (or oblique interarytenoid)

–  transverse arytenoids (or transverse interarytenoid)

•  aryepiglottic (epiglottis down) and thyroepiglottic (epiglottis up)

–  confusion regarding these muscles: not all people have this muscle fibers and still their epiglottis is moved up and down

Adduction of vocal folds

•  movement of the folds towards the midline

•  it is accomplished by gliding the arytenoids on top of the cricoid

–  lateral cricoarytenoid

–  oblique inter arytenoid

–  transverse interarytenoid

•  action of adductory muscles results in medial compression of the folds (squeeze the folds tightly at midline)

•  GLOTTAL VIBRATION CAN ONLY BE ACCOMPLISHED WHEN THE VOCAL FOLDS ARE ADDUCTED / approximated at the midline

Abduction of folds

•  movement of the folds away from the midline

•  it is accomplished by rocking the arytenoids on top of the cricoid

–  posterior cricoarytenoid

•  action of abductor muscle results in required for production of voiceless sounds

•  GLOTTAL VIBRATION CAN NOT BE ACCOMPLISHED WHEN THE VOCAL FOLDS ARE ABDUCTED

Extrinsic Laryngeal Muscles

•  suprahyoid

•  infrahyoid

suprahyoid muscles

•  one attachment at hyoid bone and the other attachment above it

•  pulls the larynx up or the tongue forward or backward

–  mylohyoid

–  geniohyoid

–  digastric

–  stylohyoid

infrahyoid muscles

•  one attachment at hyoid bone and the other attachment below it

•  pulls the hyoid bone down

–  sternohyoid

–  omohyoid

•  pulls the larynx upward

–  thyrohyoid

•  pulls the larynx downward

–  sternohyoid