Glottis

1. Overview

The glottis is the part of the larynx composed of the vocal folds (true vocal cords) and the rima glottidis—the opening between them. It plays a central role in phonation (voice production), airway regulation, and protection of the lower respiratory tract. The glottis is highly dynamic, changing its shape during breathing, speaking, and swallowing.

2. Location

The glottis is located in the larynx, at the level of the C4–C6 vertebrae in adults. Specifically, it lies:

• Inferior to the vestibular folds (false vocal cords)

• Superior to the trachea

• Within the thyroid cartilage and supported by the arytenoid cartilages posteriorly

It forms the narrowest part of the upper airway in adults and is a major regulator of airflow into the trachea and lungs.

3. Structure

The glottis consists of two main components:

• Vocal folds (true vocal cords):

  • Formed by the vocal ligament, vocalis muscle, and mucosal covering

  • Attach anteriorly to the thyroid cartilage and posteriorly to the vocal processes of the arytenoid cartilages

• Rima glottidis: The variable slit-like opening between the vocal folds

  • Changes shape depending on respiration, phonation, or effort closure (e.g., coughing)

  • Widest during deep inspiration; narrowest during phonation or forced expiration

The glottis is innervated by branches of the vagus nerve (CN X):

• Recurrent laryngeal nerve: Motor innervation to all intrinsic laryngeal muscles except cricothyroid

• External branch of the superior laryngeal nerve: Motor to cricothyroid (which adjusts vocal fold tension)

4. Function

The glottis has several core functions:

• Phonation: Vibration of the vocal cords produces sound during exhalation

• Airflow regulation: Controls the amount of air passing through the larynx into the trachea

• Airway protection: Closes during swallowing to prevent aspiration into the lower airway

• Pressure generation: Closes during the Valsalva maneuver, aiding in coughing, lifting, defecation, and childbirth

5. Physiological Role(s)

The glottis contributes to respiratory and vocal physiology in several ways:

• Sound production: Varying vocal cord tension and aperture of the rima glottidis alters pitch, volume, and tone

• Breath control: During speech and singing, the glottis modulates exhaled air precisely

• Cough reflex: Sudden glottic closure followed by explosive opening generates forceful expulsion of irritants

• Protection of lungs: Reflex closure prevents entry of food, liquids, or foreign particles during swallowing

6. Clinical Significance

Glottic Stenosis

A narrowing of the glottic space due to trauma, infection, or intubation injury. Can result in:

• Stridor (high-pitched inspiratory sound)

• Dyspnea

• Voice changes

May require surgical intervention such as dilation or reconstruction.

Vocal Cord Paralysis

Results from damage to the recurrent laryngeal nerve, leading to impaired vocal fold movement. Causes include:

• Thyroid surgery

• Lung cancer (especially left-sided due to nerve course)

• Neurological disorders

Can result in hoarseness, aspiration risk, or airway compromise.

Laryngitis

Inflammation of the vocal cords, often due to infection or overuse, affecting glottic function. Symptoms include:

• Hoarseness or loss of voice

• Throat discomfort

Usually self-limited but may become chronic in smokers or voice professionals.

Intubation Injury

Prolonged or traumatic endotracheal intubation can cause glottic edema, ulceration, or stenosis. Proper tube sizing and technique are critical to prevent damage.

Laryngeal Carcinoma (Glottic Cancer)

Cancer involving the vocal cords is one of the most common laryngeal cancers. Symptoms include:

• Persistent hoarseness

• Voice changes

• Dysphagia or airway obstruction in advanced cases

Early detection allows for excellent outcomes with radiation, surgery, or laser therapy.