Saliva Secretion and Salivary Glands (Parotid, Sublingual, Submandibular)

The three paired salivary glands and small buccal glands located throughout the oral cavity contribute to the approximately 1 liter of saliva produced in a day. Salivary flow can vary between 800 milliliters and 2 liters but this is regulated by a number of factors, especially nervous control by the brain stem.

What are the salivary glands?

The salivary glands produce and secrete saliva into the mouth cavity. There are three pairs of salivary glands :

  1. Parotid glands
  2. Submandibular glands
  3. Sublingual glands

In addition, several small salivary glands (accessory glands) are located throughout the palate, cheeks, lips, tongue and tonsils.

Composition of Saliva

Saliva is a combination of a serous and mucoid fluid. The serous fluid is watery and contains the enzyme ptyalin which the starts the digestion of carbohydrates. It is secreted by all three paired salivary glands – parotid, submandibular and sublingual. The mucus component of saliva is secreted throughout the day to moisturize the lining of the mouth and increases during eating to lubricate the food in the mouth and assist with swallowing.

It is secreted by the buccal glands of the mouth as well as the sublingual and submandibular glands. Mixed in with the mucus or ptyalin is a fluid that is high in potassium and bicarbonate ions – process explained below. The composition of saliva changes throughout the day and depending on the situation. During most of the day, when not eating, the saliva is mainly composed of mucus to keep the lining of the mouth moist.

Normal tongue

This is secreted at a rate of approximately 0.5 milliliters per minute. During eating or any other situation that triggers maximal salivation, the salivary flow can increase up to 20-fold. At these times, the rapidly exiting saliva does not contain the same quantity of potassium and bicarbonate ions since the secondary process to facilitate this cannot occur at a sufficient rate.

Additional components of saliva include thiocyanate ions, lysozymes and other proteolytic enzymes, as well as antibodies. These substances play a role in preventing infections in the mouth by destroying microorganisms and digesting any food particles that are stuck between the teeth and which may be used by the bacteria as a food source.

Secretion of Saliva

Multiple acini of the salivary glands produce saliva and then secrete it into collecting ducts where it empties into the main duct of the gland. The acini produce a ion-rich solution containing potassium, bicarbonate, sodium and chloride. This is similar to tissue fluid. Depending on the needs at the time, ptyalin and/or mucus are included in this solution. This primary secretion is not the final saliva composition that exits the gland.

As the primary fluid travels through the ducts, it undergoes a significant change in composition. First the sodium ions in the fluid are exchanged for potassium across the wall of the ducts. The fluid in the ducts now contain less sodium and more potassium. This difference in ions creates a negative electrical potential within the duct and this causes chloride to be reabsorbed.

Simultaneously bicarbonate ions are exchanged for the chloride ions and some bicarbonate is also actively pumped into the ducts. The salivary fluid now has high concentrations of potassium and bicarbonate compared to the primary secretion that initially exited the acini.

Functions of Saliva

  • Lubricate the mouth lining and food during chewing (mastication).
  • Moisten the mucosa of the mouth.
  • Ptyalin plays a small role in the digestion of starch.
  • Antimicrobial action, especially against bacteria, thereby avoiding mouth infections or slowing decay in a tooth cavity.

Nervous Control of Salivation

Parasympathetic impulses travel from the salivatory nuclei in the brain stem (“salivation centers”) reach the salivary glands via the facial and glossopharyngeal nerves. This stimulates saliva production and salivary flow.

The salivation centers may be stimulated by :

  • Impulses from the higher brain – example thinking of food that one finds delectable.
  • Impulses from the mouth and throat – taste sensations (sour and umami) and tactile sensations (smooth objects in the mouth stimulate sflow while rough objects inhibit salivation).
  • Impulses from the stomach and proximal part of the small intestine – irritation of the lining of these parts of the alimentary tract

Parasympathetic stimulation that increases salivation also increases blood flow to the salivary glands. Conversely, increased blood flow to the gland, for reasons other than parasympathetic stimulation of the gland, also increases salivation. These various factors can lead to abnormally low saliva levels (hyposalivation) or excessive salivation (hypersalivation).

Picture of Salivary Glands
(1) Parotid glands   (2) Submandibular glands   (3) Sublingual glands

Parotid Glands

Anatomy and Location

This is the largest of the salivary glands and is wedged between the ramus of the mandible (jawbone) and the mastoid process of the skull. Simply, it is located behind the angle of the jaw, slightly in front of and below the ear. The parotid gland is enveloped by a fibrous capsule known as the parotid sheath. Fatty tissue between the lobes of the parotid gland allow it a significant degree of flexibility.

Apart from being the largest gland, it is also a very significant part of the face anatomy because the parotid plexus of the facial nerve (CN VII), retromandibular vein and external carotid artery are embedded in it. It is important to note that the parotid plexus of facial nerve does not innervate the parotid gland and the retromandibular vein does not drain the gland.

The parotid gland resembles an inverted, irregularly-shaped pyramid. The apex of the gland is pointing downwards with the apex just behind (posterior) to the angle of the mandible and the base in line with the zygomatic arch. The parotid duct leaves the anterior edge of the gland, passes medially (towards the middle) through the buccinator muscle and enters the oral cavity opposite the second maxillary (upper) molar tooth.

Blood and Lymph

Oxygenated blood reaches the parotid gland via the external carotid artery which is embedded in it. Small veins drain the parotid gland and empties into the jugular veins (internal and external).

Lymph drains into parotid nodes that lie on the parotid sheath and within the gland and empties into the superficial and deep cervical lymph nodes.

Nerve Supply

The innervation of the parotid gland is via :

  • PARASYMPATHETIC (increases saliva secretion)
    • glossopharyngeal nerve (presynaptic secretory fibers) -> otic ganglion -> auriculotemporal nerve (postsynaptic parasympathetic fibers)
  • SYMPATHETIC (reduces saliva production)
    • cervical ganglia -> external carotid nerve plexus
    • great auricular and auriculotemporal nerve

Submandibular Glands

Anatomy and Location

The submandibular gland (also known as sumbaxillary gland) lies along the body of the lower jaw (mandible), extending slightly below and above the mandible. It sits in the roof of the mouth where it is divided into two lobes by the mylohyoid muscle – superficial and deep lobes. Like the parotid gland, it has an outer capsule.

The submandibular duct (Wharton’s duct) runs anteriorly and empties saliva via the sumbandibular papilla (caruncle) that is located on either side of the base of the tongue (lingual frenulum). The lingual nerve runs under the duct.

Blood and Lymph

Oxygenated blood reaches the submandibular glands via the submental artery (branch of the facial artery) and deoxygenated blood exits via the submental vein.

Lympatic vessels from the submandibular glands empty into deep cervical lymph nodes.

Nerve Supply

  • PARASYMPATHETIC (increases saliva secretion)
    • facial nerve (presynaptic parasympathetic fibers) -> chorda tympani nerve -> lingual nerve -> submandibular ganglion (postsynaptic fibers)
  • SYMPATHETIC (reduces saliva production)
    • superior cervical ganglion -> postsynaptic sympathetic fibers

Sublingual Glands

Anatomy and Location

These ovoid-shaped glands are the smallest of the salivary glands and lie deep in the floor of the mouth. The sublingual gland on each side unite to form a single mass around the root of the tongue (lingual frenulum). It does not contain a capsule like the parotid and submandibular glands.

Several sublingual ducts open into into the mouth on either side of the tongue although the largest duct may join with the submandibular duct to empty saliva through the submandibular caruncle.


Oxygenated blood reaches the sublingual glands via the sublingual branch of the lingual artery and submental artery. Venous drainage is via the sublingual and submental veins.

Nerve Supply

  • PARASYMPATHETIC (increases saliva secretion)
    • facial nerve (presynaptic parasympathetic fibers) -> chorda tympani nerve -> lingual nerve -> submandibular ganglion (postsynaptic fibers)

Last updated on September 11, 2018.

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