Transcript CDS 560- Voice Disorders Instructor

SH 598- Voice Disorders
Syllabus
• Office hours: T; TH 2-4 PM and 9-10
AM (Friday); by appointment.
• Phone: 673-3202
• Teaching Assistant: Donna Eduardo
• Required Text: Understanding Voice
Problems- Colton & Casper.
Instructional Methods
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lecture
case studies
objective exam
individual project & presentation
essay exam
directed readings
class activities
Grading
• Scale
• Critiques
• Grade postings
IMPORTANT!!
• Missing exams- Illness
• Office Hours
• Clinic office hours
Anatomy and
Physiology of Voice
Production
What is voice?
• The acoustic result of the interaction between:
– muscle groups
– cartilage's and
– the aerodynamic system.
• Three major subsystem to be concerned about:
– Respiratory
– Phonatory
– Supraglottal
Anatomy of the Larynx
• Review:
-Anatomical structures of the larynx,
including the primary cartilage's and
intrinsic and extrinsic musculature.
-The function of the individual muscles
should become a second language to
you...at least until the semester ends!
Structural Support of the
Larynx
• Larynx suspended by a single
bone: hyoid bone.
• 6 laryngeal cartilage's: 3 paired
and 3 unpaired: Provide structural
support
Laryngeal Cartilage's
• Epiglottis:
-Shaped like a long leaf,
-Base attached to inner portion thyroid
cartilage,
-Folds down over airway to protect
during swallowing.
-Composed of elastic cartilage (does not
ossify with age).
• Thyroid Cartilage:
-Angled saddle-shaped,
-Anterior attachment of true vocal folds,
-Posteriorly there are 2 superior cornu and 2
inferior cornu,
-Composed of hyaline cartilage- ossifies &
limits flexibility with age,
-Lateral walls are laminae and attach to
midline of notch.
• Cricoid Cartilage:
-Signet
ring shaped,
-2 sets of paired faces: Connects to
other joints,
-Cricothyroid joint: Connects the
cricoid to inferior cornu of the
thyroid cartilage.
Arytenoid, Corniculate & Cuneiform
Cartilage's:
-Hyaline,
-Pyramid shaped with 3 surfaces, anterior angle forms
the vocal process,
-Lateral angle: muscular process, attaches to intrinsic
muscles,
-Corniculate attached to superior tips of arytenoid
cartilage,
-Cuneiform embedded in muscular complex, superior to
corniculate: Provide no clear function, add stability for
abduction.
Laryngeal Cartilage's
• 3 Unpaired
Cartilage's
-Epiglottis
-Thyroid
-Cricoid
• 3 Paired
Cartilage's
-Cuneiform
-Corniculate
-Arytenoid
Extrinsic Laryngeal Muscles
• Three Main Purposes:
1) Fixation (primary role)
2) Elevation (move larynx up)
3) Depression (move larynx down)
• Two major groups: Suprahyoid & Infrahyoid
• Anatomical position:
Suprahyoid- Attachment lies above
hyoid bone.
Infrahyoid- Attachment lies below
hyoid bone.
Extrinsic Laryngeal Muscles
• Suprahyoid Muscles:
1) Digastricus
2) Geniohyoid
3) Hyoglossus
4) Mylohyoid
5) Stylohyoid
• Function: Raise hyoid bone &
indirectly raise larynx.
• Infrahyoid Muscles:
1) Omohyoid & Sternohyoid:
Function: Lowers the hyoid bone &
indirectly lowers larynx.
2) Sternothyroid:
Function: Lowers thyroid cartilage
& lowers larynx.
3) Thyrohyoid:
Function: Raises thyroid cartilage &
raises larynx, or with thyroid fixed lowers
hyoid.
Extrinsic laryngeal Muscles
Mandible
Ant. Digastric
Mastoid Tip
Post.
Digastric
Mylohyoid
Stylohyoid
Hyoid Bone
Thyrohyoid
Sternohyoid
Omohyoid
Sternothyroid
Sternum
Intrinsic Laryngeal Muscles
• Functions:
1) Abduction of vocal folds
for respiration,
2) Fine discrete movements
during voice production &
closure of vocal folds and,
3) Protection of trachea,
More Specifically...
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•
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Change degree of abduction/ adduction
Change mass characteristics of folds
Change tension of folds
Change length characteristics of folds
React during swallowing- closure of
folds
• Assist in muscular mechanical
advantage
Intrinsic Muscles
Action of
Cricothyriod
Pars oblique
Pars recta
• Cricothyroid: fan-shaped, 2 divisions,
Lengthens & tenses vocal folds.
Intrinsic Muscles
Thyroarytenoid
Vocal
Ligament
Thyrovocalis
Thyromuscularis
• Thyroarytenoid: muscle making up true vocal folds, 2
parts: thyrovocalis (bound to vocal ligament) &
thyromuscularis (lateral to arytenoids).
Thyroarytenoid Functions
• Decreases distance between the
thyroid & arytenoid cartilage's,
• Shortens folds,
• Decreases tension
• Decreases pitch of the voice,
• Active contraction lowers pitch of
voice.
Intrinsic Muscles
Action of Post.
Cricoarytenoid
Posterior
Cricoarytenoid
• Posterior Cricoarytenoid: Abducts the vocal folds,
actively contracted at the end of phonation & any
speech sound not requiring v.f. vibration.
Intrinsic Muscles
Action of Lat.
Cricoarytenoid
Lateral
Cricoarytenoid
• Lateral Cricoarytenoid: lies on upper surface of
cricoid cartilage, adducts vocal processes of
arytenoids closing membranous portion of v.f.’s.
Intrinsic Muscles
Transverse
Interarytenoids
Oblique
Interarytenoids
• Interarytenoids (transverse & oblique):
Unpaired, 2 part muscle, adducts v.f.’s in
cartilaginous portion by pulling arytenoid
tips together.
The Glottis
Glottis
•
•
•
•
Glottis is an open space between vocal folds.
Size is dependent on what position the v.f.’s are in.
Not a muscle or cartilage.
Abduction- open v.f.’s; Adduction- closed v.f.’s
Ventricular Folds
• False Folds,
• Superior & lateral to true vocal folds,
• Their role in phonation?
-No role in voicing
• Consist of muscle, but doesn’t have
innervation for discrete movements,
• Hyperfunctional voice?
Neuroanatomy of Vocal Mechanism
• Volitional control of laryngeal muscles:
Resides in brain.
• Connecting points in brain having a role in
control of phonation: cortex, subcortical
areas, midbrain & medulla.
• Next slides will briefly review phonation
neuroanatomy & neurophysiology.
Cortical Mechanisms of Phonatory Control
• The cerebral cortex is responsible for
conceptualization, planning, and execution
of the speech act (phonation).
• Three major areas of cortex responsible for
vocalization:
• a) Precentral & postcentral gyrus,
• b) Anterior (Broca’s) area, and
• c) Supplementary motor area.
Cortical Areas Involved in Speech Movement
Control
Premotor & Supplementary
Cortex
Primary Motor
Cortex
Somatosensory
Cortex
Broca’s Area
1. Stimulation of these areas can initiate, stop or distort vocalization.
2. These behaviors occur in dominant & nondominant hemispheres.
Speech and Phonation are Complex Motor Acts
• Involves simultaneous activation and control
of many muscles.
• Control of these motor acts occurs in cortex.
• Control of individual muscles occurs lower in
brain.
• No evidence that cortical stimulation
produces a response in a muscle.
• Higher brain function = idealization of an
event, integration of sensory information,
feedback control, and coordination of various
muscles.
Subcortical Mechanisms
• Motor cortex:connections to Thalamus, a major
portion of diencephalon or interbrain.
• Parts of diencephalon: a) hypothalamus, b)
metathalumus, c) epithalumus, d) subthalamus,
and, e) third ventricle.
• Thalamus has major pathways to motor cortex &
Broca’s area.
• Thalamus also connects to midbrain, cerebellum
and other structures in diencephalon.
Nuclei in the thalamus that project to parts of cerebral
cortex
• Motor area receives
projections from
ventrolateral nucleus.
• 1971- Found that
ventrolateral nucleus
was responsible for
initiation of speech
movements & control
of loudness, pitch,
rate & articulation.
to &
from
Sup.
Parietal
Massa
Intermedia Lobule
to & from
Prenucleus
Lateral
• Broca’s area- receives Dorsal
connections from
dorsomedian &
centromedian nuclei.
Ventral
Lateral
to &
from
Parietal
Lobe
Dorsal
Median
Ventral
posterior
Lateral
Thalamus: What Does it Do?
Projections to Cerebral Cortex
• Acts as relay for
impulses in lower
brain.
• integrates emotion
into complex
motor act.
Thalamus
Diencephalon
• Plays a major role
Midbrain
in:
Projections • coordinate
to Cerebellar
outgoing
Cortex
information:cortex
• integrating
incoming sensory
information and,
Pons
• adding emotion to
speech.
Midbrain Structures
• Midbrain (mesencephalon) lies beneath
thalamus.
• Cerebral peduncles lie on anterior surface of
midbrain and connect cerebrum with brainstem
and spinal cord.
• Posterior side has four colliculi: Superior (visual
function), inferior (audition).
• Within midbrain lies cerebral aqueduct of
Sylvius, surrounded by periaqueductal gray.
Periaqueductal Gray: What does it do?
• Stimulation of dorsal and ventrolateral areas of
periaqueductal gray = activity in some laryngeal
muscles.
• 1985- Larson reported cells in ventrolateral area
stimulate muscle activity, whereas some suppress
activity.
• Periaqueductal gray is an intermediate area
between recognition of a stimulus and production
of motor act.
Brainstem
• Bilateral structures in brainstem implicated
in neural control of phonation:
• Nucleus ambiguus
• Nucleus tractus solitarii
• Nucleus parabrachialis
• How do we know these structures
are involved in phonation?
Cerebellum
• Structure lying posterior to midbrain area.
• Control of movement.
• Three main portions: a) Vermis, b) Pars
Intermedia, c) Hemispheres
• Consists of traverse folia- increases surface
area.
• Fissura prima- fissure separating anterior &
posterior lobes.
Peripheral Connections: The Vagus Nerve
• Major nerve that supplies larynx.
• Provides sensory fibers in larynx & fibers to
control muscles of larynx.
• Cell bodies of vagus located in nucleus
ambiguus.
• Laryngeal muscles controlled by cells in caudal
portions of nucleus.
• Vagus emerges from surface of medulla
between cerebellum peduncle and inferior
olives in midbrain.
• Vagus exits skull through jugular foramen.
Distribution of Vagus (X) Nerve
Nucleus Ambiguus
chief part
Pharyngeal
Nucleus
Nerve
ambiguus
vagal accessory
Vagus (X) nerve
Vagus (X)
Nerve
Jugular foramen
Jugular
Foramen
Recurrent
Laryngeal Nerve
Superiornerve
Pharyngeal
Laryngeal
SuperiorNerve
laryngeal nerve
Cricothyroid
muscle
Vagus innervation of larynx
Nodose ganglion
Pharyngeal branch
Hyoid bone
Thyroid memb.
Thyroid gland
Right recurrent
laryngeal nerve
Sup. laryngeal
nerve
Internal SLN
External SLN
Cricothyroid memb.
Common carotid
artery
Left recurrent
laryngeal nerve
Vagus nerve
What nerve innervates the intrinsic
laryngeal muscles?
• Intrinsic laryngeal muscles are innervated
by branches of vagus (X) nerve
• The vagus nerve splits into several
branches:
1. Recurrent laryngeal nerve,
2. Superior laryngeal nerve,
3. Pharyngeal nerve.
Recurrent Laryngeal nerve of Vagus
• Courses along laryngeal branch of
inferior thyroid artery.
• It passes under caudal border of inferior
constrictor muscle.
• Divides into a motor & sensory branch
prior to entry into larynx.
• Innervates int. muscles that control
abduction/adduction of vocal folds
RLN & SLN
• Inferior Recurrent Laryngeal Branch:
– Thyroarytenoid
– Lateral Cricoarytenoid
– Posterior Cricoarytenoid
– Interarytenoids
• Superior Laryngeal Branch:
– Cricothyroid
SLN & RLN
• Ensure ability of intrinsic muscles
to move quickly & fine motor
control
• High conduction velocity
• Rapid contractions
• Low innervation per motor unit
ratio.
Conclusion
• Neurology of larynx is specific and finely
tuned
• More is known about peripheral
connections
• Less known about higher brain centers
• Coordination of respiratory, phonatory &
supraglottal areas must occur for adequate
speech production.
Readings & Directed Reading
Assignment
• For lecture - Chs. 10 & 11 in Colton &
Casper.
• Directed Reading assignment- Hoit,
J.D.(1995). Influence of body position on
breathing and its implications for the
evaluation and treatment of speech and
voice disorders. Journal of Voice, vol.9 (4):
341-347.
Activity
1) With you mouth open, hold your breath,
then abruptly release it with a vocal tone.
What physiologic events occur at the glottis?
2) Produce an /h/ sound alone. What is the
status of the glottis? How did it get there?
3) Produce an /h/ sound, then slide into
phonation. What muscles are contracting to
affect what conditions in the glottis?
More questions...
1) Place your finger on the laryngeal
prominence, alternate between high
and low pitched tones. Can you
identify a change in the position of the
larynx and describe the prime movers?
2) Can you phonate while inhaling?
What are the physiological
differences?