The glottis is the part of your larynx (voice box) that produces sound, regulates airflow during breathing, and protects your lungs from food and liquid. It consists of the true vocal cords, the space between them, and the small cartilages that pull them open or push them together. That space between the vocal cords, called the rima glottidis, is the narrowest point in your entire airway, and its ability to open wide or seal shut is what makes all three of these functions possible.
How the Glottis Produces Your Voice
Voice production starts when the vocal cords close together, narrowing or sealing the glottis. Your lungs push air upward, and pressure builds below the closed vocal cords. Once that pressure reaches a threshold, it forces the vocal cords apart, and air rushes through the gap. As air escapes, it creates a drop in pressure between the cords (the Bernoulli effect), which sucks them back together. The natural elasticity of the cords helps pull them shut as well. This cycle repeats rapidly, producing a vibration that chops the airstream into rapid pulses.
Those pulses of air travel up through your throat and mouth, where the shape of your tongue, lips, jaw, and soft palate mold them into recognizable speech sounds. The vocal cords themselves don’t vibrate like guitar strings in a simple back-and-forth motion. Different portions of each cord’s surface move inward and outward at slightly different times, creating a wave-like ripple across the tissue. This ripple is essential for sustaining vibration, because it keeps energy flowing from the airstream into the cords continuously rather than in isolated bursts.
Pitch depends largely on how tightly the vocal cords are stretched. Longer, thicker cords vibrate more slowly and produce a lower pitch, which is why men’s voices are typically deeper. The glottic opening in adult men averages about 9.8 mm across, compared to roughly 8.9 mm in women, reflecting differences in vocal cord length and laryngeal size.
How the Glottis Controls Breathing
Every breath you take involves the glottis adjusting its width. During inhalation, the arytenoid cartilages rotate the vocal cords outward (abduction), widening the opening to let air pass freely into the lungs. During exhalation, the cords drift partially inward (adduction), narrowing the gap. In one study measuring these movements, the glottic opening widened to an average area of about 126 mm² during inhalation and narrowed to about 70 mm² during exhalation. The widest and narrowest points closely aligned with the midpoint of each breathing phase rather than the very start or end.
This narrowing on the exhale isn’t random. By partially restricting outgoing air, the glottis helps maintain a small amount of positive pressure in the lungs, which keeps the tiny air sacs (alveoli) from collapsing between breaths. The exact degree of opening varies significantly from person to person, but the rhythmic pattern of widening and narrowing is consistent across healthy adults.
Protecting Your Airway
The glottis acts as a gate between your throat and your lungs. When you swallow, your vocal cords snap shut to prevent food or liquid from entering the airway. This reflex is fast and automatic. If something does slip past, the cough reflex kicks in: the glottis closes, your chest and abdominal muscles contract to build pressure behind it, and then the glottis opens suddenly, releasing a high-velocity blast of air that forces the material back up.
The same sealing mechanism is at work during the Valsalva maneuver, which you perform more often than you might realize. Straining to lift something heavy, bearing down during a bowel movement, or even bracing your core during physical exertion all involve forceful exhalation against a closed glottis. This traps air in the chest, stiffens the torso, and creates significant changes in blood pressure and heart rate. Clinicians actually use a controlled version of this maneuver to diagnose certain heart conditions, because the four distinct phases of pressure change reveal how well the cardiovascular system adapts.
What Happens When the Glottis Malfunctions
Because the glottis sits at the intersection of breathing, speaking, and swallowing, problems with it tend to be noticeable quickly. Laryngospasm is one of the more dramatic examples: the vocal cords involuntarily slam shut, and for several seconds to as long as two minutes, you can’t inhale or exhale. The sensation is one of sudden suffocation, often with voice loss or hoarseness and a high-pitched breathing sound (stridor). Episodes typically resolve on their own, but they’re frightening. Common triggers include acid reflux irritating the larynx, upper respiratory infections, severe coughing, emotional stress, and in rare cases, low blood calcium or nerve damage.
Glottic stenosis, a gradual narrowing of the glottic opening from scar tissue or inflammation, is graded on a scale from 1 to 4. Grade 1 means up to 50% of the airway is blocked, grade 2 is 51% to 70%, grade 3 is 71% to 99%, and grade 4 means the airway is completely sealed. Lower grades may cause only a breathy voice or mild exercise intolerance, while higher grades can make even resting breathing difficult. Causes include prolonged intubation (a breathing tube pressing against the vocal cords), autoimmune conditions, and trauma.
Vocal cord paralysis, where one or both cords can’t move properly, affects both voice quality and airway protection. A paralyzed cord stuck in the open position lets air escape during speech, producing a weak, breathy voice, and increases the risk of food or liquid entering the lungs during swallowing. A cord stuck in the closed position narrows the airway and can cause noisy, labored breathing.
How Doctors Examine the Glottis
The standard way to assess glottic function is flexible fiberoptic laryngoscopy, a thin camera threaded through the nose and down to the level of the vocal cords. During the exam, you’ll be asked to say “eee” so the doctor can watch both cords come together, then sniff in sharply so the cords pull apart fully. This “hee-sniff maneuver” gives a clear picture of whether each cord is moving normally, moving sluggishly, or not moving at all. The procedure takes just a few minutes and doesn’t require sedation.
For a more detailed look at how the vocal cords vibrate, a rigid videostroboscope can be placed in the back of the mouth. It uses flashing light timed to the vibration frequency, creating a slow-motion view of the mucosal wave across the cord surface. In children or in cases where neither method provides a clear enough view, direct laryngoscopy under general anesthesia may be necessary.