Larynx Anatomy

• The larynx is the organ responsible for phonation and forms a protective sphincter for the respiratory system.
• Situated in the median part of the front of the neck, corresponding to the 3rd, 4th, 5th, and 6th cervical vertebrae.
• Superiorly, it spans from the upper border of the epiglottis to the inferior border of the cricoid cartilage.
• The upper part connects to the laryngopharynx through the laryngeal inlet.
• The lower end joins with the trachea at the level of the sixth cervical vertebra.

Laryngeal Cartilages

• Single cartilages: thyroid, cricoid, and epiglottis.
• Paired cartilages: arytenoid, corniculate, and cuneiform.

Thyroid Cartilage

• It is the largest laryngeal cartilage.
• It is composed of two quadrilateral laminae fused at the front.
• The laminae are separated by a wide gap at the back.
• There is a median projection at the anterior border which forms the laryngeal prominence.
• The laminae feature a median V-shaped notch, known as the superior thyroid notch.
• The posterior borders create upward and downward projections, forming the superior and inferior horns.

Cricoid Cartilage

• It is smaller but thicker compared to the thyroid cartilage.
• It is situated below and behind the thyroid cartilage.
• Shaped like a signet ring, featuring a quadrilateral lamina at the back and a slender arch at the front.
• 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 horn of the thyroid cartilage, forming the cricothyroid joint.

Epiglottis Cartilage

• It is an elastic cartilage with a leaf-like structure.
• It extends upwards in the region behind the tongue and hyoid bone.
• The cartilage has a broad, free upper section and a narrower, tapered lower section.
• It connects anteriorly to the tongue's root through median and lateral glosso-epiglottic folds.

Arytenoid Cartilage

• Featuring a pyramidal structure with an apex, a base, and three surfaces: posterior, anterolateral, and medial.
• The apex points upwards, connecting with the corniculate cartilage.
• Its base points downwards, articulating with the upper edge of the cricoid cartilage's lamina.
• It includes a muscular process, which provides lateral extension on the lateral side and facilitates muscular attachments.
• Includes a vocal process, which is on the front side and gives rise to the true vocal cord.

Corniculate Cartilage

• It it a small cartilage is on the upper tip of the arytenoid cartilage.
• It is enclosed by the aryepiglottic fold which forms the corniculate tubercle.

Cuneiform Cartilage

• It is a small nodule found within the aryepiglottic fold.
• It contributes to forming the cuneiform tubercle.

Joints of the Larynx

• Cricothyroid joints: One on each side.
• A synovial joint located between the thyroid cartilage's inferior horn and the cricoid cartilage's side.
• Rotation is enabled between the thyroid and cricoid cartilages. -Cricoarytenoid joints: One on each side.
• A synovial joint between the arytenoid cartilage base and the cricoid cartilage lamina's upper border.
• Closing of the rima glottidis involves medial rotation and gliding, while opening involves lateral rotation and gliding.

Extrinsic Membranes and Ligaments

• Thyrohyoid membrane connects the thyroid cartilage to the hyoid bone, allowing passage for the internal laryngeal nerve, and the superior laryngeal artery and vein.
• Thyroepiglottic ligament connects the thyroid cartilage to the epiglottis and supports the epiglottis.
• Hyoepiglottic ligament connects the hyoid bone to the epiglottis and helps in affixing the epiglottis. Cricotracheal ligament connects the cricoid cartilage to the first tracheal ring and may be used for an emergency airway.

Intrinsic Membranes and Ligaments

• The vocal ligament, running from the arytenoid's vocal process to the thyroid cartilage, helps form the true vocal cord.
• The conus elasticus, also referred to as the cricovocal or cricothyroid membrane, splits into:
• A superior section, the thyroid, and the lateral part of the arytenoid's vocal process, forming the lateral part of the true vocal cord bilaterally.
• An inferior section located on the upper border of the cricoid.
• The medial part of the above mentioned conus, running from the cricoid cartilage to the thyroid cartilage, represents the initial site for establishing an emergency airway.
• The quadrangular membrane, connecting the arytenoid to the epiglottis, and supports the formation of the false vocal cord.
• The vestibular ligament is located along the free edge of the quadrangular membrane's lower border.