Salivary glands are exocrine glands. They produce saliva and deliver it through a system of ducts into the oral cavity, which is the defining feature of an exocrine gland. However, recent research has revealed that salivary glands also have some endocrine-like properties, making the full picture more interesting than a simple one-word answer.
What Makes a Gland Exocrine or Endocrine
The distinction comes down to how a gland delivers its product. Exocrine glands secrete substances through ducts onto a body surface, whether that’s your skin, the lining of your gut, or the inside of your mouth. Endocrine glands have no ducts at all. They release hormones directly into the bloodstream, which carries those chemical signals to distant targets throughout the body.
Salivary glands fit squarely into the exocrine category. Saliva forms in tiny clusters of cells called acini at the origin of the gland’s ductal system. From there, it travels through progressively larger ducts before emptying into the mouth. This duct-based delivery system is the hallmark of exocrine function.
How Saliva Is Produced and Modified
Saliva production is a two-stage process. In the first stage, acinar cells generate a primary fluid that’s isotonic, meaning it has roughly the same salt concentration as blood plasma. This initial secretion contains digestive enzymes and mucus. The cells create this fluid by actively pumping chloride ions into the duct space, which pulls sodium along with it. The resulting salt concentration draws water through the cell layer by osmosis.
In the second stage, this fluid passes through the ductal tree, where it gets significantly reworked. The ducts reabsorb sodium and chloride but are impermeable to water, so the water stays behind. The result is a final product that’s hypotonic (much lower in salt than blood) with elevated levels of potassium and bicarbonate. This bicarbonate content is what gives saliva its buffering ability, helping maintain the mouth’s pH in its normal range of 6.2 to 7.6.
What Saliva Contains
A healthy adult produces between 0.5 and 1.5 liters of saliva per day. That fluid carries a surprisingly complex mix of substances. Amylase, a digestive enzyme, begins breaking down carbohydrates while food is still in your mouth. Mucins lubricate the oral lining, protecting it from physical damage, toxins, and irritation. Antimicrobial proteins like lysozyme, lactoferrin, and peroxidase help keep bacterial populations in check, along with small defensive peptides that disrupt the cellular structure of microorganisms.
The Three Major Salivary Glands
You have three pairs of major salivary glands. The parotid glands, located in front of each ear, are the largest. The submandibular glands sit beneath the lower jaw and are the second largest. The sublingual glands, the smallest of the three, rest under the tongue. Beyond these six major glands, somewhere between 800 and 1,000 minor salivary glands are scattered throughout the lining of your mouth, throat, nasal passages, and even into the airways and middle ear. Minor glands are most concentrated along the inner cheeks, lips, tongue, and palate.
How Nerves Control Saliva Flow
Both branches of the autonomic nervous system regulate saliva production, but they do so differently. Parasympathetic nerves (the “rest and digest” system) release acetylcholine, which triggers acinar cells to produce a high volume of watery saliva. This is the dominant pathway for everyday salivation. Sympathetic nerves, the ones activated during stress, release noradrenaline, which prompts gland cells to release stored proteins rather than large volumes of fluid. That’s why your mouth tends to feel dry and thick when you’re anxious: the sympathetic system favors protein-rich, low-volume secretion over the watery flow you’re used to.
The Endocrine Side of Salivary Glands
While salivary glands are textbook exocrine glands, they don’t fit entirely in one box. Research published in Frontiers in Endocrinology has documented that salivary glands contain endocrine cells alongside their secretory and immune cells. The submandibular glands in both rats and humans produce melatonin in their striated ducts. The enzyme responsible for synthesizing melatonin has been directly identified in these structures. Evidence also supports the synthesis of steroid hormones, specifically corticosterone and testosterone, within salivary gland tissue. Estrogen receptors have been found in normal human minor salivary glands as well.
In rodents, the submandibular glands are particularly active endocrine-like organs, producing cell growth factors that enter the bloodstream. These findings have led some researchers to describe salivary glands as having a dual identity: primarily exocrine, but with genuine endocrine functions that contribute to hormonal regulation in the body. This doesn’t change their official classification. In any anatomy or physiology course, salivary glands are listed as exocrine. But the biology is more nuanced than the label suggests, and the endocrine role of these glands is an active area of investigation.