Glands of the Mouth

in animals and man, the glands that open into the oral cavity by way of ducts; the secretions of the glands of the mouth moisten and partially digest food and cover food particles with mucus, which facilitates the passage of the particles through the pharynx and esophagus.

In birds the glands of the mouth usually produce a sticky secretion during the nesting period. Among invertebrates the oral glands are usually called salivary glands; they are present in several groups of worms and in mollusks, arachnids, and most insects.

The glands of the mouth in hirudineans and a number of bloodsucking insects and acarians secrete such substances as hirudin and anticoagulin, which prevent the coagulation of the blood that these animals feed on. The secretions of the glands of the mouth of some mollusks are poisonous. The enzymes of the secretions of the oral glands in many worms and insects split carbohydrates and proteins. Multicellular oral glands are developed in all vertebrates except fish. Lampreys have a pair of suborbital oral glands. In caudate and acaudal amphibians an intermaxillary oral gland is located in the palate; in addition, acaudal amphibians have lateral palatine glands in the oral cavity.

Amphibians that have a tongue have lingual glands. In reptiles the palatine, sublingual, labial, and dental oral glands are developed. The supradental oral glands are sometimes divided into an anterior and posterior gland; in poisonous snakes the posterior gland is a poison gland—its efferent duct enters the cavity of the poison fang. In birds, especially those that are granivorous, the palatine, mandibular, and postlabial oral glands are developed.

In all mammals, except cetaceans, and in man there are numerous mucous glands of the mouth, including the labial, genal, palatine, and lingual glands, and there are also protein and mixed large salivary glands that secrete saliva.