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.
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.
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
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.
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.
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.
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.
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 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.
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.
The vocal folds consist of five layers of tissue:
Epithelial layer (thin outer layer).
Lamina Propria: Composed of two layers of elastin and one layer of collagen fibers.
Thyroarytenoid muscle: The deepest layer.
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.
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.