The glottis, otherwise known anatomically as the rima glottidis is the natural space between the vocal folds. This article will highlight the main information that is known about the rima glottidis and the surrounding internal anatomy of the larynx. It will also briefly summarize some common pathological occurrences in relation to the vocal cords.
The space between the vocal cords changes depending on the activity the larynx is involved in. During regular breathing at rest, the glottis is a narrow wedge shape, but during forced respiration it is a wide triangular shape and the vocal cords are as far apart as they can extend. During phonation, the vocal cords close and the glottis is slit-like, if apparent at all. During pronunciation, the vocal cords vibrate and produce a buzzing sound which makes up the human voice.
Internal Anatomy of the Larynx
The laryngeal cavity extends from the laryngeal inlet to the superior border of the tracheal cavity and is divided up into the vestibule, the ventricle and the infraglottic cavity. The vestibular part, which is most superior, can be found above the vestibular folds. The ventricle is the sinus between the vestibule and the vocal folds and joins the vestibule and the infraglottic cavity together. The most inferior part of the laryngeal cavity is the infraglottic cavity, which starts below the vocal cords and ends at the inferior margin of the cricoid cartilage.
The vocal folds are a paired anatomical structure that bilaterally project into the laryngeal cavity. Their function is to produce sound by allowing the free edges of the folds to vibrate against one another and also to act as the laryngeal sphincter when they are closed. The folds consist of the vocal ligament which is actually the medial free edge of the conus elasticus or cricothyroid ligament, as well as the vocalis muscle which comes from the medial fibers of the thyroarytenoid muscle and the overlying mucosa which covers it.
The vestibular folds, which are otherwise known as the false vocal cords, are folds of the mucous membrane which cover the vestibular ligaments that sit just above the true vocal cords to protect them. These folds extend between the thyroid and arytenoid cartilages.
Lastly, the ventricle of the larynx is composed of the lateral pouches that are naturally created bilaterally between the vocal and vestibular folds.
A singer’s nodule is the common name for a benign laryngeal polyp. These are usually small and are caused by overuse of the vocal cords or incessant smoking, which leads to chronic irritation. In most cases, the inflammation is limited to the true vocal cords, however this disorder has been known to extend to the adjacent structures also. It is significant because if it is on the medial side of a cord, it will obstruct the closure of the cords and create an imbalance of vocal pitch when speaking. Rest is key during the rehabilitation phase.
The benign neoplasm known as laryngeal papilloma is also found upon the true vocal cords. It is usually a single occurrence but can metastasize, especially in adults.