Three pairs of major salivary glands (parotid, sublingual,
and submandibular glands) and numerous smaller ones secrete saliva into the mouth (oral cavity), where it is
mixed with food during mastication. Saliva contains water, mucus,
and the enzyme amylase.
Functions of saliva include the following:
The saliva from the parotid gland is a rather thin, watery fluid, but the
saliva from the sublingual and the submandibular glands contains mucus and
is much thicker.
- It has a cleansing action on the teeth
- It moistens and lubricates food during mastication and swallowing
- It dissolves certain molecules so that food can be tasted (see taste)
- It begins the chemical digestion of starches through the action of amylase, which breaks down polysaccharides into disaccharides.
Structure of the salivary glands
The salivary glands are solid structures composed of millions of secretory
cells. Between the cells run tiny ducts which collect the saliva and channel
it into a single, much larger, duct. This large duct carries the saliva
away from the gland and into the mouth.
Position of the salivary glands
The position of each of the three pairs of large salivary glands is indicated
by their names. Parotid means "near the ears"; sublingual means "under the tongue"; and submandibular means "under the mandible"
(that is, under the jaw-bone).
|The parotid glands
The parotid glands are the largest of the salivary glands. They lie
just under the skin, one in front of each ear.
The saliva from each parotid gland is carried to the mouth in a small
vessel called Stensen's duct. If you look carefully inside your own
mouth you may be able to see the orifice (opening) of this duct on
the inside of your cheek, just opposite the crown of the upper second
|The sublingual glands
The sublingual glands are the smallest of the salivary glands. They
lie in the floor of the mouth underneath the tongue.
The rather special feature of these glands is that, instead of having
a single large duct like the parotid and submandibular glands, they
have a whole row of much smaller ducts. These ducts open into the
mouth along the top of the little transverse ridge which is on the
floor of the mouth under the tongue.
|The submandibular glands
The name of this salivary gland is a little confusing, for the gland
does not, in fact, lie under the mandible, but in a small depression
on the medial surface of that bone. This depression is called the
Each submandibular gland has a duct which runs forward through the
structures in the floor of the mouth, and opens by an easily seen
orifice at the base of the frenulum of the tongue.
Disorders of the salivary glands
The parotid glands can be infected with the mumps virus, and stones (calculi) can form in a salivary gland or duct. A stone
in a duct causes a swelling that enlarges during eating because saliva flow
is blocked; it pain also cause pain. Surgical removal of a stone from a
duct is usually straightforward, but if the stone is within the gland, the
entire gland may have to be removed. Poor oral hygiene may allow bacterial
infection in a gland, sometimes leading to an abscess. Tumors may develop;
however, they are rare except for a type of parotid tumor that is slow-growing,
noncancerous, and painless.
Insufficient salivation causes a dry mouth. This problem may be due to dehydration
or Sjogren's syndrome, or it may occur as a side effect of certain drugs.