•
Incisors—there are eight of these sharp front teeth used for biting into food.
•
Cuspids—these are four canine teeth used to tear food up.
•
Premolars—there are eight of these “bicuspids,” which are flatter for mashing up food.
•
Molars—there are 12 of these on the side of the mouth for crushing food. Four of these are the wisdom teeth.
The teeth are located in the tooth sockets, also referred to as the alveolar processes, located in the mandible and maxilla bones. The gums or gingivae line these tooth sockets; they participate in a minor way in securing the teeth. The periodontal ligaments mainly secure the teeth to the socket. The crown is the part above the gum line, while the root is the part below the gum line. The outer layer is the enamel, which protects the pulp cavity (where the nerves and blood vessels exist), the root canal, and the dentin, which is like bone. Outside of the dentin is a harder layer called cementum. The hardest layer (and the hardest substance in the body) is the enamel. Figure 100 shows the anatomy of the tooth:
THE PHARYNX When it comes to the digestive system, only the oropharynx and laryngopharynx participate in digestion. The oropharynx is directly behind the mouth and is where the food first enters through the fauces and into the pharynx. The laryngopharynx is just above the larynx; the
302
