The salivary glands are a group of exocrine glands located within the soft tissue of the head and neck near or within the oral cavity. They produce and excrete a substance called saliva, which is a mixture of water, electrolytes and enzymes. 

Saliva contributes to digestion by moistening and lubricating food in the oral cavity and beginning the digestion process. All salivary glands excrete saliva in the oral cavity via their ducts.

The salivary glands belong to the accessory organs of the digestive system. These glands are classified regarding their size and duct types, and they can be subdivided into the following two main groups:

• Minor salivary glands 
• Major salivary glands

Overall, the salivary glands are essential structures for digestion, maintaining oral hygiene, and speech.

Minor salivary glands

Each person has numerous minor salivary glands scattered throughout the oral cavity and oropharynx. They are embedded in the mucosa of mentioned structures and are only 0.04 - 0.2 inches (1 to 5 mm) large. They are classified depending on their location, and the most common minor salivary gland types include the following glands:

• Labial glands - located in the upper and lower lips;
• Buccal glands - found within the cheeks;
• Palatine glands - situated in the hard and soft palates; the anterior aspect of the hard palate usually does not contain any of these glands; 
• Lingual glands - found in the tongue.

Besides the mentioned glands, small amounts of minor salivary glands can also be seen within the anterior aspect of the floor of the oral cavity, tonsils, tonsillar pillars, uvula, supraglottis and paranasal sinuses. The minor salivary glands produce a relatively small amount of saliva (5 - 10%) compared to the major salivary glands. 

Most of the glands produce mucous saliva (palatine and some lingual). However, some are mixed (labial, buccal and some palatine) or even serous glands. Minor serous salivary glands are found only within the tongue and are called the lingual glands of von Ebner. They are positioned close to the foliate and circumvallate papillae. 

Recent studies have shown that there are also some minor salivary glands in the nasopharynx. These glands are called the tubarial glands.

Major salivary glands

The major salivary glands are a collection of exocrine tissue that secrete saliva through one central duct. Each person has three pairs of major salivary glands:

• Parotid gland (Read more!) - the largest salivary gland; located in front of the external ear; it secretes saliva through the parotid duct (Stensen's duct), which opens into the oral cavity opposite the maxillary second molar tooth;
• Submandibular gland (Read more!) - the second largest gland; positioned behind the mandible and under the lower jaw; it secretes saliva through the submandibular duct (Wharton's duct), which opens into the floor of the oral cavity near the frenulum of the tongue; it wraps around the mylohyoid muscle;
• Sublingual gland (Read more!) - the smallest gland; situated below the tongue; it mainly secretes saliva through the main duct of the sublingual gland (Bartholin's duct) that also opens into the floor of the oral cavity.

About 20 - 70% (usually around 20%) of people in the population present with an accessory parotid gland, referred to as the accessory lobe of the parotid gland. This accessory gland contains salivary tissue that is in close association and usually adjacent to Stensen's duct. 

Overall, the major salivary glands are the primary glands responsible for producing about 90 - 95% of saliva.

Note: To read more about the salivary glands, please visit our 3D Salivary glands article!