Final answer:
Dentin is a hard, bone-like tissue that is just underneath the enamel and cementum layers in teeth. It surrounds the pulp cavity that contains connective tissue and the pulp canal.
Step-by-step explanation:
Dentin is comparable to bone but harder, and it is deep to the cementum and enamel. The structure of a tooth includes the visible outer surface, called the crown, which is covered with enamel, the hardest material in the body. Beneath the enamel is a layer of dentin, which extends into the root of the tooth, surrounding the innermost pulp cavity. This cavity includes the pulp chamber and the pulp canal, or root canal, which is rich in blood vessels, lymphatic vessels, connective tissue, and nerves. The root of the tooth and parts of the crown are covered with cementum, a substance that helps anchor the tooth in place in the jawbone.