Larynx Anatomy

• The larynx is the organ of phonation.
• It acts as a protective sphincter for the respiratory system.
• The larynx sits in the median part of the front of the neck.
• It is opposite the 3rd, 4th, 5th, and 6th cervical vertebrae.
• It extends from the upper border of the epiglottis to the lower border of the cricoid cartilage.
• Its upper end opens into the laryngopharynx via the laryngeal inlet.
• The lower end is continuous with the trachea at the level of the sixth cervical vertebra.

Laryngeal Cartilages

• There are single and paired laryngeal cartilages

Single Laryngeal Cartilages

• Thyroid cartilage
• Cricoid cartilage
• Epiglottis cartilage

Paired Laryngeal Cartilages

• Arytenoid cartilages
• Corniculate cartilages
• Cuneiform cartilages

Thyroid Cartilage

• The thyroid cartilage is the largest laryngeal cartilage.
• It is formed of 2 quadrilateral laminae fused anteriorly.
• Posteriorly, the 2 laminae are separated by a wide gap.
• The anterior border forms the laryngeal prominence, a median projection.
• The laminae have a median V-shaped notch - the superior thyroid notch.
• The posterior borders project upward and downward, forming superior and inferior horns.

Cricoid Cartilage

• The cricoid cartilage is smaller, but thicker than the thyroid cartilage.
• It sits below and behind the thyroid cartilage.
• It has the shape of a signet ring.
• It has a quadrilateral lamina posteriorly and a narrow arch anteriorly.
• The superior border (on the lamina) articulates with the arytenoid cartilage, forming the cricoarytenoid joint.
• The inferior border (on the lamina) articulates with the inferior cornua of the thyroid cartilage, forming the cricothyroid joint.

Epiglottis Cartilage

• The epiglottis cartilage is a leaf-shaped lamella of elastic cartilage.
• It projects upwards behind the tongue and hyoid bone.
• It has an upper broad free end and a lower tapering end.
• Anteriorly, it connects to the root of the tongue via the median and lateral glosso-epiglottic folds.

Arytenoid Cartilage

• The arytenoid cartilage is pyramidal-shaped with an apex, base, and 3 surfaces: posterior, anterolateral, and medial.
• The apex is directed upwards and articulates with the corniculate cartilage.
• The base is directed downwards and articulates with the upper border of the lamina of cricoid cartilage.
• The muscular process (lateral process) extends laterally and provides for muscular attachment.
• The vocal process (anterior process) extends anteriorly and gives rise to the true vocal cord.

Corniculate Cartilage

• The corniculate cartilage is a small cartilage on the apex of the arytenoid cartilage.
• It is enclosed in the aryepiglottic fold, forming the corniculate tubercle.

Cuneiform Cartilage

• The cuneiform cartilage is a small nodule enclosed in the aryepiglottic fold.
• It forms the cuneiform tubercle.

Joints of the Larynx

• There are cricothyroid and cricoarytenoid joints.
• The cricothyroid joints; one on each side.
• They are synovial joints between the inferior horn of the thyroid cartilage and the side of the cricoid cartilage.
• They allow rotation between the thyroid and cricoid cartilages.
• The cricoarytenoid joints; one on each side.
• They are synovial joints between the base of the arytenoid cartilage and upper border of the lamina of the cricoid cartilage.
• Medial rotation and gliding close the rima glottidis.
• Lateral rotation and gliding open the rima glottidis.

Major Extrinsic Membranes and Ligaments

• Thyrohyoid membrane: Located between the thyroid cartilage and hyoid bone; allows passage of the internal laryngeal nerve and superior laryngeal artery and vein.
• Thyroepiglottic ligament: Located between the thyroid cartilage and epiglottis; holds the epiglottis to the thyroid cartilage.
• Hyoepiglottic ligament: Located between the hyoid bone and the epiglottis; holds the epiglottis to the hyoid bone.
• Cricotracheal ligament: Located between the cricoid cartilage and trachea; attaches the cricoid cartilage to the first tracheal ring and may be used in establishing an emergency airway.

Major Intrinsic Membranes and Ligaments

• Vocal ligament: Located from the arytenoid (vocal process) to the thyroid cartilage; helps form the true vocal cord.
• Conus elasticus: Also known as the cricovocal or cricothyroid membrane.
  • Lateral part of conus elasticus: Located at the Superior aspect —thyroid, vocal ligament, arytenoid (vocal process) and Inferior aspect —upper border of cricoid; the lateral part of the conus elasticus is bilateral and helps form the true vocal cord.
  • Medial part of conus elasticus: Located from the cricoid cartilage to the thyroid cartilage; it is the primary site for establishing an emergency airway.
• Quadrangular membrane: Located from the arytenoid to the epiglottis; helps form the false vocal cord.
• Vestibular ligament: Located at the free edge of the inferior border of the quadrangular membrane.