2/11 SHS Lecture

Anatomy and Physiology of the Larynx

  • Introduction to the Larynx

    • The larynx serves multiple purposes:
    • Acts as a valve system for airways.
    • Aids in waste excretion from both ends of the body.
    • Used for sound production, known as phonation.

  • Phonation Process

    • Phonation can be compared to blowing a raspberry:
    • Involves lips coming together and airflow causing vibration.
    • Lips can vibrate at speeds faster than muscular movement alone.
    • Lips typically vibrate at a frequency of 120 to 200 times per second;
    • Singing can increase this to 400 to 600 vibrations per second for males;
    • Females can reach frequencies in the thousands.

  • Myoelastic-Aerodynamic Theory of Phonation

    • A prominent theory explaining phonation.
    • Key components of the theory:
    • Myo - refers to muscle.
    • Elastic - indicates the property of being flexible and returning to original shape after deformation (like an elastic band).
      • An elastic structure can deform but snaps back to its original shape.
    • Aerodynamic - discusses airflow across a surface.
    • The theory is termed a “theory” because not all aspects of voice production are fully understood.
    • Physiologically, it’s essential for individuals to be able to pull vocal folds together and generate enough air pressure to initiate vibration.

  • Timbre

    • Timbre refers to the quality of a voice or sound that differentiates it from others.
    • Unique anatomical structures contribute to each person’s timbre:
    • Vocal folds contribute to timbre.
    • Structures above vocal folds further shape tone.
    • Analogous to how musical instruments create unique sounds.
    • Vocal folds have a structure akin to musical strings, comprising a core (the vocal ligament) and surrounding tissues (referred to as ligaments).

  • Human Larynx Anatomy

    • Specific anatomical landmarks:
    • Epiglottis - a C-shaped structure that aids in swallowing.
    • Arytenoids - two prominent bumps located on the posterior aspect of the larynx, involved in vocal function.
      • Arytenoids help in positioning and tension of vocal folds.
    • Vocal folds are also termed vocal cords.
    • False Vocal Folds - also known as ventricular folds, located above the true vocal folds.
    • Areapiglottic Fold - the tissue fold connecting the epiglottis to the arytenoids.
    • Piriform Sinuses - spaces on either side of the ventricular folds.
      • Important for swallowing; can pool fluids.
    • Valliculae - the space between the tongue and epiglottis.
      • Important for swallowing, providing an area for food passage.

  • Physiological Notes

    • The anatomy facilitating phonation and contributing to tone (timbre) is crucial for sound production.
    • Muscles contribute to voice quality and sound generation; injury to any of these structures can influence vocal performance.
    • Dehydration and poor vocal habits can lead to issues like mucus production imbalance, swelling, or soreness.
    • Muscular injuries can arise due to trauma or neurological conditions, significantly impacting speech and swallowing ability.

  • Muscles of the Larynx

    • Major intrinsic muscles involved in laryngeal action:
    • Thyroarytenoid Muscle: connects thyroid cartilage to arytenoids.
      • Main muscle contributing to vocal fold tension and closure.
    • Vocalis Muscle: part of the thyroarytenoid that directly influences vocal fold tension.
    • Muscularis Muscle: helps adjust tension and position of vocal folds.
      • Both the vocalis and muscularis contract to close vocal folds for phonation.
    • Lateral Cricoarytenoid Muscle: closes vocal folds in a specific angle.
    • Posterior Cricoarytenoid Muscle: uniquely abducts, or opens, the vocal folds.
    • Naming conventions for muscles often reflect their attachments and locations (e.g., lateral, superior).
    • Cricothyroid Muscle: facilitates the rocking motion to stretch or compress vocal folds, altering pitch.
    • Transverse Arytenoid Muscle: adducts the vocal folds, aiding in phonation.
    • Thyroepiglottic Muscle: connects thyroid to epiglottis, aids in positioning.
    • All muscles are essential for fine motor control in producing a variety of pitches and volumes, allowing for vocal flexibility.
    • The relationship between muscle contraction and sound production is similar to how different musical instruments can be played to achieve the same note through various techniques.

  • Clinical Implications

    • Common vocal pathologies can arise from misuse or injury to the laryngeal structures.
    • Conditions may manifest as swelling, nodules, or trauma affecting vibratory quality.
    • Monitoring and understanding anatomical and physiological processes is crucial for effective therapeutic interventions in individuals with voice disorders.