1. Epithelium 

• Thin and stiff

• Maintains the shape of vocal fold

2. Superficial layer of the lamina propria

• Reinke’s space

• Consist of loose fibrous components, which can be known as a mass of soft gelatin

3. Intermediate layer of the lamina propria

• Consist of elastic fibers

• Like bundle of soft rubber bands

4. Deep layer of the lamina propria

• Consist of collagenous fibers and somewhat like a bundle of cotton thread

5. Vocalis Muscle

• Constitutes the main body of the vocal fold and is like a bundle of stiff rubber bands.

Vocal fold vibration – sequence of vibratory cycles:

The low pressure created behind the fast-moving air column produces a “Bernoulli effect” which causes the bottom to close, followed by the top. Closure of the vocal folds cuts off the air column and releases a pulse of air

• Situated between vertebrae C3-C6

• Not rigidly fixed in the neck 

• Capable of limited up-down, and side-to-side movements

Larynx movements serve primarily to help protect the airway from aspiration of food or liquid.

Extrinsic (external) Muscles:

1. Respiration 

2. Phonation

3. Resonance

Describes how the relative stiffness and compliance of the layers of the VF’s contributes to the vibration of the VF’s (how the stiffness of the VF’s have an effect on the vibration of VF’s)

Five layers of the VF’s are placed under THREE vibratory divisions (based on biomechanical properties): 

1. Compliant cover

2. Stiffer transitional zone

3. Least compliant body

    

    

   SUMMARY: The cover-body theory is a theory that explains how the stiffness of the VF’s have a direct effect on the vibration of the VF’s using biochemical properties, divided into three groups. → Compliant cover, Stiffer transitional zone, and least compliant body.

The myoelastic aerodynamic theory is responsible for explaining the elastic recoil that pulls the vocal folds together, and blows them apart. Before phonation, the vocal folds are adducted. As subglottal pressure increases, the vocal folds are forced open, and air rushes through the glottis.

‘Myo’: involvement of muscles

‘Elastic’: ability of those muscles to return to original shape

‘Aero’: airflow and pressure

‘Dynamic’: movement and change.

putting myoelastic theory and cover body theory together. Understanding the fundamentals of energy exchange provides insight into the physics of VF oscillation and coal efficiency in normal and pathological situations.

These Self-sustained oscillations of VF’s are a result of: 

• Coupling between the aerodynamic energy → Which is transferred to the VF’s → biomechanical structure of the VF;s → acoustic loading of the vocal tract

  The rate of energy transfer from the fluid of the VF tissue → directly correlated with the PRESSURE and VELOCITY fields within the GLOTTIS.

1. The VF’s adduct (come together), once fully closed, there is increase in subglottal air pressure

2. The increased subglottal pressure causes VF to separate, causing them to abduct (open) completely (not necessarily widely) 

3. A puff of air is released as the VF’s abduct (seperate completely)

4. The decreased air pressure & elastic recoil of VF causes them to move back towards midline

5. The VF’s approximate first on the inferior border and then on their superior border, eventually adducting, but not all the way

6. The Vf’s have completed one cycle due to: Myoelastic-aerodynamic forces, not simply repetitive muscle contraction.

Perceptual attribute correlated with change in the rate of VF vibration

• Length of VF’s

• Tension of VF’s

• Mass of VF’s 

• Subglottal pressure

(LOUDNESS) 

• Subglottal pressure

• Medial compression of VF’s

• Duration, speed and degree of closure

• Supralaryngeal adjustments

• The glottal source (voice source)

• The resonant characteristics of vocal tract (anything that makes noise)

Pediatric Larynx: 

Position: 

• Infants’ Larynx is located high in the neck (C1 and C3)

• The tip of epiglottis touch the velum

• Starts to descend (in the neck) at around 2yrs old. 

Size: 

• Smaller than adult larynx

• Thyrohyoid membrane is much shorter

• Length of VF’s is 2.5-3.0 mm

• Larynx reaches full size during puberty

• Length if VF gradually continues until 20 years of age

Shape: 

• Shaped like a funnel

• Becomes cylindrical with age

Consistency: 

• Cartilages are soft and liable: allows for growth and protection

• VF mucosa is thinner in newborns and young children

 International classification of functioning & measure health and disability

The ICF framework/model can be used in interprofessional collaborative practice and person-centered care.

1. Functioning and disability (those life areas impacted in the activities/participation in relation or due to the impairment) 

1. Body functions and structures: describes actual anatomy/physiology of the human body

2. Activity and Participation: describes a person's functional status (communication, mobility, learning, applying knowledge, etc.) 

2. Contextual factors (not part of an individual's health condition, race, religion, etc.) 

1. Environmental factors: factors that aren’t within the person’s control. (family, work, government agencies, laws, and cultural beliefs). 

Personal Factors: Include race, gender, age, educational level, etc. These personal factors typically arent coded in ICF although they may influence how a person functions.

• based on etiology (Consequence of disease) but as a component of health.

Global level

• Organization (people) dedicated to the well-being of people

• They are guided by science

• Also used to protect people from now being products

• How all medical people talk to each other, on a global level- usually in numbers. Use codes. 

• Provides critical knowledge on the extent, causes and consequences of human disease via data that is reported and the clinical terms coded with ICD.

• Allows the systematic recording, analysis, interpretation, and comparison of mortality and morbidity data collected in different countries or regions and at different times. 

• Functional 

• Organic

• Structural 

• Neurological

• Psychogenic

• Other

• VD that results in inefficient use of the vocal mechanism when the structure is NORMAL (most common type of VD)

CAUSES: vocal abuse, phonotrauma-yelling, excessive cough, muscle tension, vocal fatigue, ventricular phonation

Organic:

Structural:

Neurological:

• Organic: VD that results from physical changes in the vocal mechanism (not born with it). This is not something that the person has done to harm the vocal tract, this is anatomical. 

  Structural: vocal fold abnormalities (vocal nodules, edema, inflammation of larynx). Neurological: result from problems with the central or peripheral nervous system (paralysis, M.S. parkinsons)

• False vocal fold use during phonation 

Reason: true V.F’s will not come together- False VF make up for them

• These patients are not willingly experiencing voice limitations. 

• They do have disordered voice due to psychologically damaging circumstances (sometimes these can go away in 1 session)

• Abnormal and inappropriate pattern of adduction (closing) during inspiration -breathing

• Stress and exercise may cause

• Can be environmentally stimulated - asthma, chemicals

Response: Increase tension, causes trauma to vf’s (vf’s come together while trying to breathe in.)

• Typically caught in early infancy

• Laryngeal function/structure collapses

• Aeratnodes-come together for false v.f’s

• This is treated through surgery and we work on feeding, swallowing, language, the whole 9 yards.

• Buildup of mass on VF

• In PAIRS

• White-ish on glottal margin of each VF

• Swelling in VF’s- change in vocal quality

Causes: singers, whispering

• Breathiness

• Decreased habitual pitch

• Decreased loudness

• Hoarse quality

• Vocal fatigue

• Localized FLUID FILLED sac on VF (blister like)

Sessile: adhere to mucosal surface (top layer)

Pedunculated: attached by stim stalk (large-floppy)

• Closed sac filled with fluid or a semisolid substance

• Usually only happen on 1 side

• Benign

• Unilateral

• Inner margin