Illustration of mouth and salivary glands
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After you take your first bite of pie, your salivary glands produce saliva — a mixture of secretions that help lubricate and break down food. Besides the salivary glands in the lining of your mouth, you have three pairs of larger salivary glands — the parotid, sublingual and submandibular glands. You typically produce about 2 pints (about 1 liter) of saliva a day.

Not all of the work is chemical, though. As you savor the bite of pie, your teeth work to break down the pie while your tongue mixes it with saliva. This action transforms it into a soft, moist, rounded mass (bolus) suitable for swallowing.