Laryngeal Anatomy and Physiology Lecture Review

Laryngeal Cartilages

• The thyroid cartilage is connected to the cricoid cartilage through a joint.

• Posterior View:

  • Epiglottis.

  • Arytenoid cartilages (paired) sit atop the cricoid cartilage.

  • Paired cartilages: Arytenoid, Corniculate, Cuneiform.

  • Unpaired cartilages: Thyroid, Cricoid, Epiglottis.

Extrinsic Muscles of the Larynx

• Functions:

  • Hold the laryngeal mechanism in place within the anatomy.

  • Help elevate the larynx within the vocal tract.

  • Help depress the larynx.

  • Support the positioning of the laryngeal mechanism in the neck.

• Three Primary Functions:

  1. Elevation of the larynx:

     • Occurs during swallowing (larynx goes up and out, due to extrinsic muscles).

     • Plays a minor role in manipulating the cricothyroid cartilage for pitch.

     • Involved in singing.

  2. Depression of the larynx:

     • Used for inspiration (inhalation).

  3. Support of the laryngeal mechanism in the neck.

• Categories of Extrinsic Muscles:

  • Suprahyoid Muscles:

    • Located above the hyoid bone.

    • Primarily responsible for elevating the larynx.

    • Examples: Mylohyoid, Digastric.

    • Important in medical settings for classification.

  • Infrahyoid Muscles:

    • Located below the hyoid bone.

    • Primarily responsible for depressing the larynx.

    • Depress the hyoid and larynx as they are interconnected.

• Overall Role: These muscles work together to aid in safe swallowing and to facilitate a full breath (inspiration).

• A reference chart for medical settings would include muscle, function, origin, insertion, and cranial nerve innervation.

Intrinsic Muscles of the Larynx

• All five intrinsic muscles of the larynx are paired.

• They are crucial for both this course and for professional practice.

• Thyroarytenoid Muscle (Vocalis Muscle):

  • Function: Shortens the vocal folds when it contracts.

  • Location/Connection: Originates from the anterior thyroid cartilage and inserts into the arytenoid cartilage.

  • Significance: It is the deepest layer of the vocal fold (most medial/within the vocal fold structure).

  • Includes sub-sections: Thyromuscularis and Thyrovocalis.

• Posterior Cricoarytenoid Muscle:

  • Location: Posteriorly situated, connecting the cricoid and arytenoid cartilages.

  • Function: The only intrinsic muscle responsible for abduction ($AB$ -duction) of the vocal folds, opening them. It moves the lateral processes of the arytenoid medially, causing the vocal processes to abduct.

• Lateral Cricoarytenoid Muscle:

  • Location: Lateral to the cricoid, connecting to the arytenoid cartilages.

  • Function: Initiates the process of adduction ($AD$ -duction) of the vocal folds, pulling them inward.

• Interarytenoid Muscles (Oblique and Transverse Arytenoid):

  • Location: Connect from one arytenoid cartilage to another.

  • Function: Along with the lateral cricoarytenoids, they complete true vocal fold adduction ($AD$ -duction) by tightening them like a corset, ensuring no gaps. This is vital for protecting the airway during swallowing.

  • Oblique and Transverse arytenoids are sub-sections of interarytenoids.

• Cricothyroid Muscle:

  • Function: Primarily involved in pitch change.

  • Achieves pitch change by elongating/stretching and condensing the vocal folds.

  • It causes the thyroid cartilage to tilt closer to or away from the cricoid cartilage:

    • Tilting the thyroid closer to the cricoid elongates the true vocal fold.

    • Relaxing (moving the thyroid away from the cricoid) condenses the true vocal fold.

Laryngeal Membranes and Ligaments

• Overall Function: These structures hold all the laryngeal cartilages together, acting like a sling to ensure seamless movement and control of the laryngeal mechanism as one unit.

• Extrinsic Membranes:

  • Connect the laryngeal mechanism to structures outside the larynx.

  • Thyrohyoid Membrane: Connects the thyroid cartilage to the hyoid bone (superiorly).

  • Cricotracheal Membrane: Connects the cricoid cartilage to the trachea (inferiorly).

• Intrinsic Membranes:

  • Connect each of the laryngeal cartilages together within the laryngeal structure.

  • Line the laryngeal interior to create a continuous membrane (e.g., between epiglottis, vocal folds, subglottal area).

  • Ensure continuity as seen during scoping (no spaces).

• Ligaments:

  • Are thicker connective tissues compared to membranes.

  • Further help everything stay in place and move together during elevation and depression.

  • Hyothyroid Ligament: Connects the inner surface of the thyroid cartilage to the hyoid bone.

  • Cricothyroid Ligament: Connects the thyroid to the cricoid cartilages.

  • Cricotracheal Ligament: Connects the cricoid to the trachea.

  • Both membranes and ligaments are very important for swallowing.

Aryepiglottic Fold

• Location: A fold that extends bilaterally between the arytenoid cartilage and the epiglottis.

• Contents: Contains the cuneiform and corniculate cartilages, as well as mucous glands.

• Function of Embedded Cartilages:

  • The cuneiform and corniculate cartilages provide pliability but prevent the aryepiglottic fold from being sucked inward or collapsing during inspiration or swallowing.

  • Without these cartilages, the tissue would be too pliable and collapse.

Laryngeal Cavities (Glottis and Surrounding Spaces)

• The glottis serves as the central reference point.

• Glottis: The space between the true vocal folds, located at the level of the vocal folds.

• Supraglottic: The cavity located above the glottis.

• Subglottic: The cavity located below the glottis.

• Order: Supraglottic $\rightarrow$ Glottis $\rightarrow$ Subglottic $\rightarrow$ Trachea.

• These terms (supraglottic, glottic, subglottic) are used to refer to disorders or pathologies within the larynx.

Ventricular (False) Vocal Folds

• Location: Sit slightly superior and lateral to the true vocal folds.

• Attachments: Attach to the arytenoids posteriorly and just below the epiglottis at the level of the thyroid cartilage anteriorly.

• Composition: Made of mucosis glands and fibroelastic tissue, allowing movement without easy fatigue.

• Functions:

  • Crucial for swallowing.

  • Act as a protective barrier to prevent pathogenic particles or agents from reaching the true vocal folds.

  • Considered