VOICE DISORDERS Chapter 11

***Review notes from AUS 304, Anatomy & Physiology of Phonatory System ***Chapter 11 – Anatomy review at beginning of chapter  Structures of the Laryngeal Skeleton (Table 11.1)  Structures within the Larynx (Table 11.2)  Structure of the True Vocal Folds, & Hirano’s Cover-Body Model (Table 11.3).  Intrinsic Muscles of the larynx (Table 11.4)  Innervation of the Larynx – (Table 11.4)

Anatomy of the Larynx

 The larynx or voicebox is situated on top of the trachea where the aerodigestive tract splits into two separate pathways.  It consists of a framework of cartilage with surrounding soft tissues  It serves three important functions:

1. Control of airflow during breathing 2. Protection of airway (by closing off the trachea during swallowing) 3. Production of sound for speech

Laryngeal Cartilages

Cricoid:

 Ring-shaped cartilage that sits on top of the trachea

Thyroid:

 Cartilage positioned on top of the cricoid cartilage

 Shield-shaped and most prominent of the laryngeal cartilages

 The cricothyroid joint permits rocking and gliding motion of the thyroid

Epiglottis:

 Leaf-shaped cartilage that covers the laryngeal vestibule during swallowing

Arytenoids:

 Two small pyramidal shaped cartilages that sit on top of the cricoid (form the cricoarytenoid joint)

 Play a critical role in phonation

 The true vocal fold attach at one end of the arytenoids

 Many muscles attach to muscular process (on the back of the arytenoids) and can move in different ways: Laryngeal Muscles Movement of larynx is controlled by two groups of muscles:

1. Intrinsic: muscles that move vocal folds and other muscles within larynx 2. Extrinsic: position the larynx in the neck also called “strap muscles”

Intrinsic Muscles:

PCA or posterior cricoarytenoid:

LCA or lateral cricoarytenoids:

IA or interarytenoids:

TA or thyroarytenoid:

CT or cricothyroids: Laryngeal Spaces

Glottis: Refers to the space between the vocal folds

Anterior commissure: Where the VFs attach to the thyroid cartilage

Posterior glottis:

Vocal Folds (See Hirano’s Cover-Body Model)

Cover = Mucosa Body = Muscles

1. Cover has two layers: (see web cross-section fig) 1.Epithelium:

2.Lamina propria:

2. Body: made up of thyroarytenoid muscle Vocal Fold Motion (web fig mucosal wave)

1. Vocal folds at rest are:

2. For speech, muscle contraction brings the folds together

3. Pressure builds

4. Folds are blown apart

5. Folds come back together via 2 things:

6. Cycle repeats Mucosal wave: folds do not open all at once; rather the bottom part opens first then the top part opens. A good mucosal wave is necessary for the folds to open in a uniform and symmetric fashion for optimal voice quality.

Neural Control of Larynx (See Fig) Vagus Nerve (CN X) has three branches that innervate the larynx.

1. Pharyngeal Branch

2. Recurrent Laryngeal Nerve (RLN)

3. Superior Laryngeal Nerve (SLN): as 2 branches of its own:

a. Extrinsic

b. Intrinsic Physiology of the Larynx

1. Changing Frequency of VF vibration heard as “Pitch”

Three mechanisms alter the frequency of vocal fold vibration:

1. Mass

2. Length

3. Tension

2. Changing Loudness

1. Increase subglottal pressure (pressure below the VFs)

2. Increase medial compression of the folds

3. Increase amplitude of articulatory movements (doesn’t play as crucial a role as other 2)