Ch.4 Anatomy Phonation

Spoken Communication

• Voicing (Phonation)

  • Phonation: The product of voiced and unvoiced phonemes.

  • Phonemes: Sounds of speech produced through vocal folds.

  • Voiced Phonemes: Produced with vocal fold vibration.

  • Unvoiced Phonemes: Air flows through the vocal tract without vibrations.

• Cognate Pairs:

  • Most voiced phonemes have an unvoiced pair (e.g. 'b' vs 'p').

  • Lack of vocal fold movement results in unvoiced sounds.

  • Phonation is essential for speech, while respiration provides energy.

• Larynx:

  • Principal function is airway protection during swallowing; non-biological function includes voicing.

  • Structure: Musculo-cartilaginous, situated at the midline in the pharynx.

Structure of the Larynx

• Musculo-cartilaginous structure located superior to the trachea and inferior to cervical vertebrae C4-C6.

• Unpaired Cartilages: Epiglottis, Thyroid Cartilage, Cricoid Cartilage.

• Paired Cartilages: Arytenoid, Cuneiform, Corniculate.

  • Important to build each cartilage for understanding the larynx structure.

Laryngeal Membranes and Ligaments

• Membranes and ligaments connect laryngeal cartilages.

• Extrinsic Membranes:

  • Thyroid Membrane: connects thyroid cartilage to hyoid bone.

  • Ligaments connecting hyoid bone to epiglottis, thyroid cartilage, and more.

• Intrinsic Ligaments: Connect cartilages, maintain form and support of larynx.

  • Major components include:

    • Fibroelastic Membrane

    • Quadrangular Membrane

    • Conus Elasticus

    • Vocal Ligament

Vocal Folds

• Composition: Five layers of tissue involved in vibration.

  • Outside layer: Squamous Epithelium (pearly white appearance).

  • Superficial Lamina Propria: Contains elastin fibers, provides cushion and stretch.

  • Intermediate Lamina Propria: Cross-layered elastin fibers, adds strength.

  • Deep Lamina Propria: Made of collagen fibers, limits extension (provides strength).

  • Vocal Ligament: Combination of intermediate and deep lamina propria.

• Function of Vocal Folds:

  • Vibration is caused by approximation (adduction) of folds, while abduction allows for breathing.

Phonation Theories and Vocal Health

• Cover-Body Theory: Describes how the cover (layers of folds) and body (muscle) contribute to vibration.

• Vocal health is influenced by internal (hydration, health) and external (environment, smoke) factors.

  • Staying hydrated is essential; external irritants can compromise vocal quality.

Laryngeal Cavity and Spaces

• Classification of spaces helps in identifying issues or neoplasms.

• Key Spaces:

  • Aditus: Entrance to the larynx from the pharynx.

  • Vestibule: Area between aditus and ventricular folds (false vocal folds).

  • Ventricle: Space between true and false vocal folds.

  • Glottis: Space between vocal folds; variable depending on activity.

  • Supra- and Subglottic Spaces: Areas above and below the glottis, respectively.

Cartilages of the Larynx

• Unpaired Cartilages:

  • Thyroid Cartilage: Largest cartilage with specific landmarks (angle, notch).

  • Epiglottis: Floppy, protective structure over the airway during swallowing.

• Paired Cartilages:

  • Arytenoid Cartilages: Crucial for the movement of vocal folds.

  • Cuneiform Cartilages: Provide structure to epiglottis folds.

  • Corniculate Cartilages: Provide support and structure to the epiglottic folds and play a role in the overall function of the larynx, particularly in assisting with the regulation of airflow during phonation and protecting the airway during swallowing.

Laryngeal Musculature

• Intrinsic Muscles:

  • Responsible for fine motor movements (adduction, abduction, pitch adjustments).

  • All innervated by the vagus nerve.

• Extrinsic Muscles:

  • Include laryngeal elevators and depressors (above or below hyoid bone).

  • Primary functional roles in speech production, elevation, and swallowing.

• Specific Muscles:

  • Adductors: Close vocal folds (e.g. lateral cricoarytenoid).

  • Abductor: Opens vocal folds (posterior cricoarytenoid).

  • Tensors: Adjust pitch (cricothyroid).

  • Relaxers: (thyroarytenoid) contribute to lowering pitch.

Interaction Between Structures

• Interaction between intrinsic and extrinsic laryngeal muscles is essential for vocal function.

• Sustained laryngeal positions achieved mainly by extrinsic muscles, while intricate vocal adjustments handled by intrinsic muscles.

• Movements of the tongue also influence laryngeal position and thus pitch.

Larynx Structure and Function

The larynx is a musculocartilaginous structure located at the upper end of the trachea, composed of:

• Cartilages:

  • Unpaired: Cricoid, Thyroid, Epiglottis

  • Paired: Arytenoid, Corniculate, Cuneiform

• Articulations:

  • Thyroid and Cricoid cartilages articulate at the cricothyroid joint, allowing them to come closer together in front.

  • Arytenoid and Cricoid cartilages articulate, permitting a wide range of arytenoid motion.

  • Corniculate cartilages rest on arytenoids; Cuneiform cartilages reside in the aryepiglottic folds.

  • The epiglottis protects the airway during swallowing.

The cavity of the larynx is a constricted tube lined with:

• Smooth mucous membrane covering its surface.

• Sheets and cords of ligaments connecting the cartilages.

• Associated ligaments include:

  • Thyrohyoid membrane, lateral thyrohyoid ligament, median thyrohyoid ligament (covering the space between the hyoid bone and thyroid).

  • Hyoepiglottic and thyroepiglottic ligaments attaching the epiglottis to the hyoid and thyroid.

Key anatomical features include:

• Valleculae: Folded areas between the tongue and epiglottis.

• Cricotracheal ligament: Connecting the trachea to the larynx.

• Fibroelastic membrane: Includes upper quadrangular membranes and aryepiglottic folds, lower conus elasticus, and the vocal ligament.

• Pyriform sinus: Space between the aryepiglottic membrane and thyroid cartilage laterally.

Vocal Folds

The vocal folds consist of five layers of tissue:

1. Epithelial layer (thin outer layer).

2. Lamina Propria: Composed of two layers of elastin and one layer of collagen fibers.

3. Thyroarytenoid muscle: The deepest layer.

4. The vocal ligament is made of elastin.

• The aditus serves as the entryway into the vestibule of the larynx.

• Ventricular and vocal folds are separated by the laryngeal ventricle; the glottis is the variable space between the vocal folds.

Cartilages and Muscles

The laryngeal cartilages include several important landmarks for muscle attachment:

• Articular facet for arytenoid cartilage: Allows rocking, gliding, and limited rotation.

• Cricoid cartilage: Shaped like a signet ring, with a higher back.

• Thyroid cartilage: Features two prominent laminae, superior and inferior horns, and a thyroid notch.

  • Attached to the hyoid bone at the superior cornu and to the cricoid cartilage at the inferior horn.

Intrinsic Muscles: Fine motor control (adduction, abduction, pitch adjustments), all innervated by the vagus nerve.Extrinsic Muscles: Influence laryngeal positioning; include both infrahyoid and suprahyoid muscles such as:

• Elevators: Digastricus, mylohyoid, hyoglossus, and geniohyoid muscles.

• Depressors: Sternohyoid, sternothyroid, and omohyoid muscles.

• Thyropharyngeus, thyrohyoid, and cricopharyngeus: Elevate the larynx.