Final answer:
The dentin forms a hard walled cavity that protects the pulp in a tooth. It is covered by enamel, the hardest material in the body.
Step-by-step explanation:
The hard walled cavity that contains and protects the pulp in a tooth is called the dentin. The dentin is a bone-like tissue that surrounds the pulp cavity, which contains blood vessels, lymphatic vessels, connective tissue, and nerves. It is covered by an outer layer of enamel, which is the hardest material in the body.