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.

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