The human mouth has many functions, including the formation of speech and aiding in breathing, but the three main digestive purposes the mouth has are:

• the intake of food
• the beginning of mechanical digestion
• swallowing

  Although the existence of the mouth may seem elementary to life as an animal, it's interesting to note that our two separate openings for food and waste are found only in the larger, more differentiated animals. Many species of animal posses only one opening for both functions and no canal through the body. Since humans evolved from these lower animals, human embroys similarly form a one-way body cavity and anus first during development and differentiate the mouth structure only later (this is a principle of developmental biology.)

  The human mouth is lined with mucous membranes that protect the outer cell layer of the body cavity (the epithelium) from abrasive food and harmful digestive juices while the food passes through the upper alimentary canal. The mucous membrane, along with the submucosa and the serosa, is actually present throughout the entire alimentary tract. However, the mouth and esophagal mucous membranes are not involved in adsorption as their intestinal couterparts are, and subsequently these have a different morphology (stratified, squamous cells.)

  The mouth also bears teeth which aid in the mechanical digestion according to their shape and position. The crown (covered in a shiny layer of enamel) sticks out of the gum, while the root is implanted in the alveolar bone (and is encased in cementum.)

 Children have 20 deciduous teeth and adults have 32 permanent teeth. They are only truly specialized in adults, but in general, they are the incisors, canines, premolars, and molars. Incisors have the cutting function of mastication or chewing of food. Canines are sometimes called cuspids and pierce and tear food that is being eaten. Premolars/bicuspids and molars/tricuspids have large, flat surfaces with two or three grinding cusps on their surface. Then a small rounded mass of food called a bolus is formed so that it can be swallowed easily.

 The bolus is a mixture of the solid food particles reduced in size and saliva. The action of swallowing begins with the elevation of the tongue against the top of the palate to separate a bolus of food. The tongue then propels the separated food into the oropharynx, the upper pharynx, where the process continues.