The parotid glands are located on either side of the lower jaw below the ear. The submaxillary or submandibular glands  are located along the jaw bone on either side of the head. The sublingual glands spread out and cover the area beneath the mucous membrane of the floor of the mouth located toward the chin. These sublingual glands are not visible because when the tongue is raised they remain under the mucous membrane that covers the floor of the mouth and toward the chin, spread out over this area.

The floor of the mouth becomes prominent upon raising the tongue and at the midline, appearing as an elevated fold of mucous membrane a ridge can be seen that binds each lip to the gums. On each side of this ridge on the floor of the mouth is a slight fold called the sublingual papilla, from which the sublingual glands open. Running outward and backward from each sublingual papilla is a ridge (the plica sublingualis) that marks the upper edge of the sublingual (under the tongue) salivary glands and onto which most of the ducts of that gland open.

The sublingual gland secretes a mixed substance known as saliva. The sublingual glands are unlike the other two major salivary glands, both of which also secrete this mixed substance (saliva), in that they (sublingual glands) are not encapsulated in a capsule of tissue which is found  surrounding the other two major salivary glands, the parotid and submaxillary (also called the submandibular). The sublingual glands have many ducts (Rivinius ducts) that empty where the floor of the mouth and the tongue meet.

Several combine to form what is called Bartholin’s ducts which are the larger of the major ducts of the sublingual glands which empty into the submaxillary duct. These major salivary glands secrete a  mixed fluid that is mainly mucus (saliva). They are exocrine glands (glands that secrete their products (enzymes) into ducts).