The submandibular gland produces the majority of your saliva when you’re not eating. Sitting beneath your jawbone on each side, this pair of glands generates roughly 65% of your resting saliva, making it the single largest contributor to the fluid that keeps your mouth moist, protects your teeth, and starts the digestive process.
Where the Gland Sits
Each submandibular gland weighs about 7 to 8 grams and sits in a small triangle formed by the lower border of the jawbone and the muscles of the neck. The upper surface of the gland rests partly against a shallow depression on the inner surface of the jaw and partly on the mylohyoid muscle, the flat sheet of muscle that forms the floor of your mouth. The gland wraps around the back edge of that muscle, with a deeper portion extending inward toward the tongue.
Saliva leaves the gland through a narrow tube called the submandibular duct, which is about 5 centimeters long and 1.5 millimeters wide. The duct travels forward and upward, crossing paths with the nerve that provides sensation to your tongue, before opening into the mouth at a small bump on the floor of the mouth just beside the frenulum (the thin fold of tissue under your tongue). You can sometimes feel this opening with the tip of your tongue.
What It Produces
The submandibular gland makes a mixed type of saliva that’s mostly watery but has a slight thickness to it. About 90% of the gland’s secretory cells produce a thin, enzyme-rich fluid, while the remaining 10% produce mucus, a thicker substance that helps lubricate food for swallowing. The mucus-producing cells are typically clustered together with crescent-shaped caps of the watery cells sitting at their edges.
This blend gives submandibular saliva a useful dual character. The watery component carries digestive enzymes that begin breaking down starches the moment food enters your mouth. The mucus component coats food particles, making them easier to chew and swallow, and also forms a protective film over the soft tissues lining your mouth and throat. Together, these secretions help neutralize acids produced by oral bacteria, wash away food debris, and deliver minerals like calcium and phosphate that strengthen tooth enamel.
How It Contributes to Daily Saliva
Your body produces saliva continuously, even when you’re not eating. During this unstimulated, resting state, the submandibular glands are responsible for about 65% of the total output. That makes them far more important to baseline mouth moisture than the parotid glands (the larger glands near your ears), which take over as the dominant producers only when you’re actively chewing or tasting something sour or flavorful.
This resting contribution matters more than it might sound. Baseline saliva is what keeps your mouth comfortable overnight, protects your teeth between meals, and maintains the chemical balance that prevents harmful bacteria from gaining a foothold. When submandibular function drops, the effects on oral health can be significant: increased cavities, gum disease, difficulty swallowing, and a persistent feeling of dryness.
How the Brain Controls Secretion
Saliva production isn’t something the gland does on its own. It’s triggered by signals from the nervous system. The submandibular gland receives its primary instructions through a branch of the facial nerve, which carries parasympathetic signals (the “rest and digest” signals) to a cluster of nerve cells called the submandibular ganglion. From there, nerve fibers reach the gland and tell it to ramp up secretion.
This is why your mouth waters when you smell food, see something appetizing, or even think about eating. Sensory input triggers the parasympathetic pathway, and the gland responds within seconds. The same nerve signals also widen blood vessels supplying the gland, increasing blood flow so the gland has the raw materials it needs to produce saliva quickly. Sympathetic nerves (the “fight or flight” system) also connect to the gland, but their role is more about adjusting the protein content and thickness of saliva than increasing volume.
Why It’s Prone to Salivary Stones
Of all the salivary glands, the submandibular is the most likely to develop salivary stones, small hardened deposits that can block the duct and cause painful swelling. Several features of the gland make it vulnerable. Its duct is long, narrow, and runs upward against gravity, giving minerals more time and opportunity to settle. Its saliva is naturally higher in calcium and phosphate than saliva from other glands, and these minerals are already at concentrations where they can begin to crystallize.
Stones form when calcium phosphate (in a mineral form called hydroxyapatite) deposits around bits of debris in the duct. Research on patients with salivary stones has found that their submandibular saliva has significantly higher calcium concentrations than normal, along with lower levels of magnesium and citrate, two substances that normally act as crystallization inhibitors. In other words, it’s not just that there’s more calcium available to form stones; the natural braking mechanisms are also weaker.
A blocked duct typically causes swelling and pain under the jaw that gets worse during meals, when the gland is trying to push saliva through an obstructed tube. Small stones sometimes pass on their own, especially with hydration and gentle massage. Larger ones may need to be removed through a minor procedure.
Blood Supply to the Gland
The submandibular gland gets its blood primarily from the facial artery, which curves around the lower edge of the jaw and sends branches directly into the gland tissue. The submental artery, a branch of the facial artery, also contributes. Additional blood may come from the lingual artery and the external carotid artery. Venous blood drains through the anterior facial vein and smaller veins that travel alongside the arteries. This rich blood supply is essential: producing saliva requires filtering large volumes of fluid from the bloodstream, and the gland needs constant delivery of water, electrolytes, and proteins to keep up with demand.