The larynx, also known as the voice box, or the glottis, plays an essential role in human speech and is a flexible segment of the respiratory system. An epithelium-lined tube formed off nine pieces of cartilage bound together by several ligaments connects the pharynx to the trachea. It extends from the fourth to the sixth cervical vertebral level anteriorly to the oesophagus. It plays a vital role in the respiratory tract by allowing air to pass through it while keeping food and drink from blocking the airway.
The different sections of the larynx
- Epiglottis is a thin, leaf-shaped flexible flap structure at the most superior region of the larynx made of elastic cartilage with a mucous membrane. It acts as a switch between the larynx and the oesophagus to permit air to enter the airway to the lungs and food to pass into the gastrointestinal tract. In a relaxed position, the epiglottis projects up the larynx in swallowing. The superior part will move down the larynx and close the trachea windpipe entrance.
- Glottis is an opening between the vocal folds located inferior to the epiglottis. It is about 2.5 cm long from the anterior to the posterior. It is considered generally as the primary valve between the lungs and the mouth. It leads into the windpipe, where the largest cartilage supports it in the larynx, the thyroid cartilage. There are four different ‘states of the glottis’ open, in vibration, narrow and closed.
- Thyroid cartilage is the largest cartilage in the larynx, which supports the Glottis. It is semicircular in shape and has a prominent ridge that extends from its anterior surface. In males, this ridge is larger and known as Adam’s apples. It is connected by a wide ligament called the thyrohyoid membrane to the hyoid bone at the superior surface. The thyroid cartilage anchors the anterior end of the vocal fold attached to the inside of the thyroid cartilage near the body’s midline.
- Cricoid cartilage is hyaline cartilage and is the most inferior structure of the larynx located at the level of the sixth cervical vertebra. It forms the connection between the larynx and the trachea. It is ring-shaped, the posterior portion is wider than the anterior portion, giving space for forwarding movement of the neck. It is connected superiorly to the thyroid cartilage and inferiorly to the trachea by cricotracheal ligament. Posteriorly the Cricoid cartilage almost touches the thyroid cartilage to form what is called the cricothyroid joint. Through changes in the angle of the cricothyroid joint the pitch of the sound can be modified to help control the tension of the vocal folds.
- Cuneiform, corniculate, and arytenoid cartilages are three tiny, paired massed cartilage. Positioned posterior to the thyroid on either side of the sideline of the larynx.
- Arytenoid cartilages sit on the posterior side of the cricoid cartilage and are pyramidal masses of cartilage. They play a vital role in producing sound and act as the pivot point for the vocal fold and the muscles that move the vocal folds.
- Corniculate cartilages rest on top of the arytenoid cartilages, they are horned shaped and help support the posterior end of the glottis.
- Cuneiform cartilages are thin bands of cartilage that laterally extends to support the lateral sides of the glottis from the corniculate cartilages.