Untitled Flashcards Set

Larynx Structure 

The larynx is a musculo-cartilaginous structure.

  • Located at the superior (upper) end of the trachea.

  • Main function: protecting the airway and the lower respiratory tract.

  • Cartilages are bounded by ligaments and lined with mucous membranes.


Cartilage Rings

Composed of THREE UNPAIRED CARTILAGES

  • Unpaired: only one.

    • Thyroid: The biggest Cartilage.

      • Above the cricoid cartilage.

      • The epiglottis is attached to the thyroid.

    • Epiglottis: Flexible, leaf-shaped.

      • Protects the airway

    • Cricoid: Ring

      • Sits on top of the trachea.

      • LAST PART of the larynx.


Also composed of THREE PAIRED CARTILAGES

  • Paired: a set of cartilages.

    • Arytenoids: Pyramid shaped

      • Sits on top of the cricoid (superior posterolateral surface).

      • Houses the Vocal Folds:

        • One end attaches to the thyroid cartilage and the other on the arytenoid cartilage.

    • Corniculate: 

      • Sit on the apex (on top of the arytenoids), projecting posteriorly to form the peak of the pyramid.

      • Base (inferior surface): It’s concave surface is the point of articulation with the convex arytenoid facet of the cricoid cartilage.

    • Cuneiform: Small cartilages embedded within the aryepiglottic folds.

      • Situated above and anterior to the corniculate cartilages.

      • Causes a small bulge on the surface of the membrane that looks white under illumination.


Larynx Location

The larynx sits on top of the last ring of the trachea.

  • It is adjacent to cervical vertebrae 4 through 6.

    • C4-C6

      • But the larynx of an infant is located higher.


The entire larynx is strung from the hyoid bone.

  • NOT APART OF THE LARYNX.


Average Length

Males: 44 mm

Females: 36 mm


The Trachea

Composed of a series of cartilage rings connected and separated by a fibroelastic membrane.


Thyroid Cartilage 

The largest cartilage of the larynx (unpaired).

  • Prominent anterior surface:

    • Made up of two plates called the thyroid laminae joined at the midline at the thyroid angle.


Thyroid Notch: V-shaped depression located at the superior-most point of the thyroid angle.


Laryngeal prominence (or Adam’s apple): 

  • Visible and palpable protrusion in the larynx.

    • More prominent in men than women.

      • Due to the angle being smaller in males (thyro angular).


The posterior aspect of the thyroid has two prominent sets of horns (or cornua)

  • Superior horn: Project superiorly to articulate with the hyoid bone.

  • Inferior horn: Project downward to articulate with the cricoid cartilage.



Cricoid Cartilage 

It is a complete ring resting on top of the trachea.

  • The most inferior cartilage of the larynx.

    • It is the approximate diameter of the trachea.

  • HIGHER in the back than the front.


The superior facets are for articulation with the arytenoid cartilages.

  • The cricoarytenoid joints: Permit the rotation of the arytenoid cartilages on the cricoid.

The lateral-inferior facets are for articulation with the inferior horns of the thyroid cartilage.

  • The cricothyroid joints: Permit the rotation of the inferior horns of the thyroid cartilage on the cricoid.



Membrane vs. Ligament:

If the membrane is thick, it’s a ligament. If it’s sheet-like, it’s just a membrane.


Vocal ligament: The superior margin of the conus elasticus (the red lines) forms the vocal ligament, the base of the vocal folds.


Median cricothyroid ligament + conus elasticus = cricothyroid membrane.



Epiglottis

The unpaired epiglottis is a leaflike structure.

  • Arises from the inner surface of the angle of the thyroid cartilage just below the notch, being attached there by the  thyroepiglottic ligament.


The epiglottis covers the entrance of the trachea.

  • Keeps food from going down the trachea rather than the esophagus.


The sides of the epiglottis are joined with the arytenoid cartilages via the aryepiglottic folds.


Swallowing

During swallowing, food passes over the epiglottis, and, from there, laterally to the pyriform sinuses.

  • Pyriform sinuses: Small fossae or indentations between the aryepiglottic folds medially and the thyroid cartilage.


Arytenoid and Corniculate Cartilages

Vocal Processes

The vocal processes of the arytenoid cartilages project anteriorly toward the thyroid notch. The posterior portion of the vocal folds attaches to the vocal processes.



Muscular Process

Forms the lateral projection of the arytenoid pyramid.

  • Is the point of attachment for muscles that adduct and abduct the vocal folds.



Hyoid Bone

Unpaired.

  • NOT a bone of the larynx.


Forms the union between the tongue and the laryngeal structure.

  • Articulates loosely with the superior horn of the thyroid cartilage.

  • ONLY BONE of the body that IS NOT attached to another bone.


Three major elements of the hyoid bone:

  1. The corpus: Body of the hyoid is a prominent shield-like structure forming the front of the bone.

  2. Greater cornu: Arises on the lateral surface of the corpus, projecting posteriorly.

  3. Lesser cornu: At the junction of the corpus and greater cornu.


Nine muscles attach to the hyoid bone.


Movement of the Cartilages:

Cricothyroid Joint

  • This synovial joint is the junction of the cricoid cartilage and the inferior horn of the thyroid cartilage.

  • Permits the thyroid cartilage to:

  1. Rock down in front.

  2. Glide forward and backward slightly.

  • Provides major adjustments for change in vocal pitch.

    • Especially increasing fundamental frequency.


NOTE: When this muscle contracts, the thyroid cartilage tilts forward.



THE CT MUSCLE → Contracts → The thyroid cartilage glides forward and downward → Because the vocal folds are attached to the inner surface of the thyroid cartilage → They elongate → Their tension increases → FO (Pitch) increases.



Cricoarytenoid joint

  • This synovial joint is the articulation formed between the cricoid and arytenoid cartilages.

    • Permits:

  1. Rocking motion

    1. Anterior-posterior movement of the arytenoids over the cricoid cartilage.

    2. Brings the two vocal processes toward each other → permitting the vocal folds to approximate (abduction).

  2. Gliding (sliding) motion

    1. Anterolateral movement of the arytenoids on the cricoid cartilage.
      Facilitates changes in vocal fold length.

  3. Minimal rotation of the arytenoid cartilage.

    1. This motion is limited to extremes of abduction.

      1. Too much movement can cause dislocation.