TOOTH

plural Teeth, any of the hard, resistant structures occurring on the jaws and in or around the mouth and pharynx areas of vertebrates. Teeth are used for catching and masticating food, for defense, and for other specialized purposes. The teeth of vertebrates represent the modified descendants of bony dermal (skin) plates that armoured ancestral fishes. A tooth consists of a crown and one or more roots. The crown is the functional part that is visible above the gum. The root is the unseen portion that supports and fastens the tooth in the jawbone. The root is attached to the tooth-bearing bonethe alveolar processesof the jaws by a fibrous ligament called the periodontal ligament or membrane. The neck of the root is embraced by the fleshy gum tissue (a specialized area of mucous membrane that lines the mouth cavity). The shape of the crown and root vary among different teeth and among different species of animals.