The sudden spray of liquid from your mouth during a wide yawn is a common and entirely harmless physiological event, often informally referred to as “gleeking.” This unexpected squirt is not water, but rather a jet of saliva propelled by the forceful muscle contractions that accompany a deep yawn. The phenomenon is a simple mechanical reaction, resulting from temporary pressure built up in the structures responsible for producing and releasing saliva. Understanding this process requires looking closely at the anatomy in the floor of the mouth and the powerful movements involved in yawning.
The Saliva Factory: Key Anatomy
The source of the unexpected spray is a pair of major salivary glands located in the lower portion of the mouth: the sublingual and submandibular glands. These glands sit just beneath the tongue and the floor of the mouth, producing a significant portion of the saliva that keeps the mouth moist and aids in digestion. The saliva produced by these glands must exit into the oral cavity through small openings called ducts. The submandibular gland primarily empties its contents through Wharton’s duct, which opens via a tiny nozzle located near the base of the tongue. While these ducts usually allow saliva to drain steadily, their location makes them vulnerable to external pressure from sudden, intense movements.
Jaw Movement and Pressure Build-Up
The act of yawning is a complex reflex that involves a massive, involuntary stretching of the facial, jaw, and throat muscles. During a yawn, the jaw is opened to its maximum extent, and the muscles in the neck and throat undergo a strong, sustained contraction. This wide opening and stretching motion has a direct impact on the submandibular and sublingual glands. The forceful extension of the jaw causes the muscles in the floor of the mouth to become taut and compress the underlying structures. This muscular contraction acts like a powerful squeeze on the salivary glands, trapping saliva within the duct system and causing a rapid accumulation of pressure, similar to squeezing a filled toothpaste tube.
The Mechanism of Forced Expulsion
The final squirt occurs when the concentrated pressure inside the duct system finds a sudden release point. The narrow opening of the duct acts like a small nozzle, and the highly pressurized saliva is forced out at a high velocity. This rapid release of built-up fluid pressure is what creates the characteristic jet or spray that appears to shoot from under the tongue. The position of the tongue during a yawn often contributes to the direction and velocity of the expelled saliva. As the jaw extends, the tongue tends to retract and press down or backward, which further compresses the area and guides the stream forward. This involuntary squirt is a simple side effect of anatomy and physics colliding during a powerful reflex.