Larynx

Larynx

• The larynx is the start of the lower respiratory tract.
  • Some sources will include the larynx in the upper respiratory system, whereas others divide it into the upper and lower respiratory systems with the vocal cords as the cut off; others use the epiglottis as the cut off.
• Superiorly, the larynx is attached to the hyoid bone via connective tissues.
• Three key functions of the larynx:
• It conducts air from the pharynx to the trachea.
• It prevents food and liquid from entering the lower respiratory tract.
• It facilitates the production of speech.

Key anatomical structures:

Three larger, singular cartilages:

• Thyroid cartilage – forms anterior and lateral walls; features the laryngeal prominence.
• Cricoid cartilage – circular, forms base of larynx.
• Epiglottis – "flap" that attaches to the internal surface of the thyroid cartilage, anteriorly, and projects posteriorly and superiorly over the opening of the larynx.
  • Upon swallowing, the flap closes off the entryway to the larynx, which prevents foods and liquids from entering the lower respiratory tract.

Three paired sets of smaller cartilages:

• Arytenoid cartilage – articulates with cricoid cartilage posteriorly.
• Corniculate cartilage – sits on arytenoid cartilages.
• Cuneiform cartilage – sits anterior to corniculate cartilages; very small, wedge-shaped.

Membranes and connective tissues:

• Thyrohyoid membrane - connects the thyroid cartilage and hyoid bone.
• Cricothyroid ligament - extends superiorly from the cricoid cartilage to the thyroid and arytenoid cartilages.
• Vocal ligament - thickened superior edge of the cricothyroid ligament comprises the vocal ligament; known as the "true" vocal cord because it facilitates sound production.
• Rima glottides - opening between the vocal cords. During sound production, laryngeal muscles contract to rotate the arytenoid cartilages and alter the opening between the true vocal cords.
• Quadrangular membrane - connects the lateral sides of the epiglottis to the arytenoid cartilages.
  • Free edges of the quadrangular membrane thicken to form the:
    Aryepiglottic ligament, superiorly
    The vestibular ligament, inferiorly

The vestibular ligament and its mucosal covering are often referred to as the "false vocal cord"; it does not participate in sound production.

Clinical correlations:

Laryngitis is inflammation of the vocal cords, which can stem from infectious or non-infectious causes (such as over-use). It typically results in hoarseness but severe swelling can block the airways.