CODI 504 - Voice Disorders
Lecture 1 :  Review of Laryngeal Anatomy & Physiology

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1. Connective Tissues: Hyoid Bone

•  Horseshoe - shaped
•  Suspended by muscles & ligaments
•  Landmarks
• Corpus (body
• Greater horn
• Lesser horn

2. Connective Tissues: Laryngeal cartilages

•  Hyaline cartilage - softer and more flexible than bone
•  Major cartilages
•   Thyroid
•    Superior & inferior cornu, lamina
•    Thyroid notch
•   Cricoid
•    Ring-shaped, connects with upper tracheal ring
•    Articulates with arytenoids & thyroid
•   Arytenoids (paired)
•    Pyramidal in shape - 4 surfaces/3 angles
•   Vocal and muscular process

3. Connective Tissue:  Laryngeal Cartilages

•   Epiglottis
•   Leaf-shaped
•   Attaches to interior surface of thyroid
•   Aids in directing food/liquids during swallow
•   Corniclulate
•   A pex of arytenoid
•   Cuneiform
•   Embedded in aryepiglottic folds

4. Connective Tissue: Laryngeal Cartilages

• Joints and articulation
• Cricothyroid joint - rocking (tilting) motion & slight anteroposterior movement
• Cricoarytenoid joint - gliding (anterior-posterior plane) motion and rocking(mediolateral) motion
• Ligaments & membranes
• Thyrohyoid ligament
• Thyrohyoid membrane
• Cricothyroid ligament (medial & lateral)

5. Laryngeal Cavity:  Landmarks

• Lined with fibroelastic membranes covered with epithelial tissue
• 3 regions: supraglottal, glottal, subglottal
• Space between vocal folds is called the glottis
• Anterior 2/3 called membranous glottis
• Posterior 1/3 called cartilaginous glottis

6.  Muscles of the Larynx:  Intrinsic Muscles

• Functions
• Adduct & abduct glottis
• Change relative position of cartilages
• Change dimensions & physical properties of vocal folds
• Modify laryngeal airway resistance
• Thyroarytenoid
• 2 muscle groups - thyrovocalis & thyromuscularis
• Decrease distance between thyroid/arytenoid
• Shortening vocal folds, decrease tension, increase mass(thicken)
• Cricothyroid
• 2 divisions -pars rectus & pars oblique
• Decrease space between thyroid/cricoid therefore increasing space between thyroid/arytenoid
• Lengthens vocal folds, decreases mass (thins) and increases tension
• Posterior Cricoarytenoid
• Abducts arytenoids by rocking backwards
• Rotates vocal processes laterally
• Opens glottis
• Lateral Cricoarytenoid
• Rotation of vocal processes medially
• Tilting of arytenoids forward
• Closes (adducts) membranous portion of glottis
• Interarytenoid muscle
• Two-part muscle
• Oblique and transverse fibers
• Adducts arytenoids, closing cartilaginous portion of glottis

7.  Neural Innervation of  Intrinsic Muscles

•  Neural innervation from 2 branches of vagus (CN X)
•  Superior laryngeal branch - CT
•  Recurrent (inf) laryngeal branch - all others
•  Both branches composed of axons with cell bodies in brainstem nuclei of CN X and CN XI
•  Right RLN loops around subclavian artery & ascends to larynx
•  Left RLN loops around aorta and ascends

8.  Muscles of the Larynx:  Infrahyoids

•  General function - lower larynx, lengthen vocal tract
•  All innervated by CN XII
•  Sternohyoid - Lowers larynx indirectly
•  Sternothyroid - Lowers larynx directly
•  Omohyoid - depresses or retracts hyoid or pulls it to rt/lf
•  Thyrohyoid - elevates thyroid/lowers hyoid

9.  Muscles of the Larynx:  Suprahyoids

•  Forms sling supporting hyoid & indirectly supporting larynx
•  Stylohyoid - elevates & retracts hyoid (larynx indirectly)
•  Digastric - together elevate hyoid/lower mandible
•  Anterior belly - elevation/anterior movement of hyoid
•  Posterior belly - elevation/posterior movement
•  Mylohyoid - elevates hyoid (along with larynx and tongue)
•  Geniohyoid - anterior movement of hyoid (slight elevation)

10.  Muscles of the Larynx:  Neural Innervation of Suprahyoids

•  CN V - mylohyoid & anterior belly of digastric
•  CN VII - Stylohyoid & posterior digastric
•  CN XII - Geniohyoid

11.  Sensory (afferent) Innervation of the Larynx

•  Afferent information carried via SLN and RLN
•  Sensory receptors are embedded in the mucosal linings, in joints & in muscles
•  Mucosal receptors in supraglottic areas signal larynx to close
•  Mucosal receptors in subglottic areas signal adductor muscles to increase activity and decrease abductor activity
•  Exact feedback function of joint/muscle receptors not clear

12.  Morphology of Vocal Fold Tissue

•  Vocal folds are layered with specialized tissues in each layer
•  Epithelium
•  Lamina propria
•  Superficial layer
•  Intermediate layer
•  Deep layer
•  Muscular layer (thyrovocalis)
•  Epithelium & superficial layer of lamina propria called cover
•  Intermediate and deep layers form vocal ligament & called transition
•  Muscular layer called body