The mouth is the entrance to the digestive tract. It is lined with mucous membranes. At the top part of the mouth is the palate. The palate is divided into the bony hard palate at the front and the fleshy soft palate at the rear of the mouth. The uvula is the piece of dangling soft tissue in the middle of the throat and it is flanked on both sides by the tonsils at the opening to the throat (pharynx).

At the floor of the mouth is a bundle of muscles that forms the tongue. Tiny bumps called papillae cover the top of the tongue, and each contains tiny pores known as taste buds. Individual taste buds located all over the tongue are designed to sense sweet, salty, sour, bitter or umami (“savory”) tastes. Three pairs of salivary glands in the mouth secrete saliva, a substance containing a digestive enzyme (amylase) that begins to break down carbohydrates before food enters the stomach. Saliva also helps to cleanse the mouth, teeth and gums, acting as an important barrier to tooth decay.

The lips are covered with skin on the outside and mucous membranes on the inside. The inside portion of the lips is connected to the gums. The orbicularis oris is the major lip muscle that controls the movement of the lips. Underlying blood vessels cause the lips to appear darker then other facial skin.

During their lifetime, humans have two sets of teeth that form in the mouth. The first set of 20 primary teeth usually begins to erupt between 6 months and 1 year old. Most children have all their primary teeth by age 3. By the time a child is around 6, a second set of 32 permanent teeth begin to erupt. With proper care, these teeth will last for the rest of the person’s lifetime.

There are several types of permanent teeth. The square teeth called incisors are located in the front of the mouth, with four on the bottom and four on top. Sharp teeth called canines (also called eye teeth) are located on either side of the incisors. The incisors and the canines are used to bite into and tear food.

Behind the canines are the premolars (also known as bicuspids). Four premolars (made up of two sets) are located in each jaw. Behind the premolars are the molars which have the largest chewing surfaces. There are 12 molars total, with six in each jaw. Molars are the last three teeth on each side in both the upper and lower jaws. They are known as the first, second and third molars. The molars have grooves (fissures) and points (cusps) which are designed to grind food.

The third molars are also known as the wisdom teeth. They are the last teeth to come in, and often cause complications that require them to be removed.

All of the permanent teeth erupt in phases that roughly correspond to the following ages:

• 6 to 7 years: first molars
• 6 to 9 years: incisors
• 9 to 12 years: canines
• 10 to 12 years: premolars
• 11 to 13 years: second molars
• 17 to 21 years: third molars (wisdom teeth)

The mouth and teeth work together to begin the process of digesting food. Once food enters the mouth, the teeth begin to break it down. Incisors cut the foods and canines tear it. The premolars grind and mash food. Molars are responsible for the most vigorous chewing of food. As food is being chewed the tongue pushes the food up against the teeth.